THE NEXT GENERATION VIRGO CLUSTER SURVEY. X. PROPERTIES OF ULTRA-COMPACT DWARFS IN THE M87, M49, AND M60 REGIONS

The NGVS is a deep optical imaging survey in the u*, g, i, and z bands, with additional partial coverage in r, carried out with MegaCam, the 340 megapixel camera on CFHT (Boulade et al. 2003).²⁴ The survey covers an area of Ω = 104 deg² inscribed within the virial radii of the Virgo A (R₂₀₀ = 1.55 Mpc) and Virgo B (R₂₀₀ = 0.96 Mpc) subclusters (Ferrarese et al. 2012), which are centered on M87 and M49, respectively. Beginning with the NGVS "pilot program" (see Ferrarese et al. 2012), images were collected during six consecutive observing seasons, 2008 through 2013. Each MegaCam pointing (i.e., NGVS field) measures roughly 1° × 1° on the sky. There is some overlap between fields, so that the 104 deg² survey area is covered by 117 distinct NGVS pointings. Each NGVS field is assigned a pair of ordered numbers according to its location within the survey grid. Field (+0, +0) is in the cluster center and includes M87; the field numbers grow with increasing right ascension and declination. In addition, four background fields were also observed (see Table 1 of Ferrarese et al. 2012). The background fields are located well beyond the survey boundaries (offset from M87 by ≈16°), at about three virial radii from the center of the A subcluster and at Galactic latitudes corresponding to the highest and lowest values spanned by the main survey.

Exposure times in seconds for the five filters are:

$$\begin{eqnarray}{T}_{{u}^{*}} & = & 11\times 582=6402\\ {T}_{g} & = & 5\times 634=3170\\ {T}_{r} & = & 7\times 687=4809\\ {T}_{i} & = & 5\times 411=2055\\ {T}_{z} & = & 8\times 550=4400\end{eqnarray} \tag{ 1 }$$

Different dithering patterns were used for the different filters with the exception of the g and i bands which shared an identical strategy. In the g-band, the limiting magnitude for point sources is 25.9 mag (10σ) while the surface brightness limit for extended sources is μ_g ∼ 29.0 mag arcsec⁻² at 2σ above the mean sky level. This means that the NGVS is roughly three magnitudes deeper than either the Sloan Digital Sky Survey (SDSS; York et al. 2000) or the Virgo Cluster Catalog (VCC; Binggeli et al. 1985). In addition, the NGVS image quality is excellent: the FWHM for every image, in all filters, is always better than 1''. The best seeing conditions were reserved for the i band, where the FWHM never exceeded 06, with a median of 054. The g band images have longer exposure time and the larger FWHM with a median of 080 (Ferrarese et al. 2012).

The pre-processing for all NGVS images includes bad pixel masking, overscan and bias subtraction, flat fielding, fringing correction (which is necessary only for the i and z bands) and scattered light correction. The individual images are then corrected for a global background map and stacked using the MegaPipe pipeline (Gwyn 2008) with the adoption of an artificial skepticism method (see Ferrarese et al. 2012 for details). The final stacks are then photometrically and astrometrically calibrated to SDSS images and scaled to have photometric zero point of m_AB = 30.

For the Virgo core region centered on M87 (a 3.62 deg² survey that is comprised of the NGVS+0+0, NGVS+0+1, NGVS-1+0, and NGVS-1+1 fields), a deep K_s band imaging survey (Next Generation Virgo cluster Survey—InfraRed, hereafter NGVS-IR) was also carried out with CFHT, using the WIRCam instrument (see Muñoz et al. 2014 for more details). The NGVS-IR has a limiting magnitude of K_s ∼ 24.4 mag (5σ) for point sources and a surface brightness limit of ${\mu }_{{K}_{s}}\simeq 24.4$ mag arcsec⁻². The seeing was always better than 07, with the median seeing of the stacked mosaic being 054. The NGVS-IR raw images were processed using the 'I'iwi processing pipeline v2.0,²⁵ with cosmic rays removed and saturated pixels corrected. After the sky removal, the images were stacked together using the SWARP software package (Bertin et al. 2002). Full details on NGVS-IR reductions can be found in Muñoz et al. (2014).

To construct an NGVS compact-source catalog, SExtractor (Bertin & Arnouts 1996) was first run on each NGVS field in double image mode. Objects were detected in the g-band images using SExtractor parameters: DETECT_THRESH = 1.5, ANALYSIS_THRESH = 5.0, DETECT_MINAREA = 2.0, DEBLEND_NTHRESH = 32.0 and DEBLEND_MINCONT = 0.002, and then measured in each of the u*griz images. More than 25 million objects were detected and measured across the 117 NGVS fields. All the objects were detected on the MegaPipe global background stacked images, which have the highest photometric accuracy for point-like sources such as stars and GCs. Note, however, that this catalog is not suitable for investigations of extended objects, especially low surface brightness galaxies. Future papers in this series will discuss the identification and characterization of extended sources in the survey.

By contrast, UCDs at the distance of Virgo are both bright and compact (see, e.g., Haşegan et al. 2005 for an early demonstration of this based on HST/ACS imaging) so we expect to detect virtually every UCD in the cluster. As discussed below, the main obstacle facing a systematic study of UCDs in Virgo is the high level of contamination from stars, compact background galaxies and spurious features such as asterisms or blends.

While UCDs are often taken to have half-light radii, r_h, larger than 10 pc, the exact dividing point with GCs is somewhat arbitrary. Nevertheless, the great majority of GCs are smaller than r_h ∼ 10 pc; in the Virgo cluster, which lies at a distance of 16.5 Mpc (Mei et al. 2005; Blakeslee et al. 2009), the average GC half-light radius is 2.7 ± 0.35 pc ∼ 0035 (Jordán et al. 2005, similar results can be found in Webb et al. 2013). By contrast, the half-light radii of known UCDs span a range, from 11 to 93 pc with a median of ∼20 pc or 025 (Haşegan et al. 2005; Evstigneeva et al. 2008). Virgo galaxies are much larger than GCs or UCDs: i.e., the effective radii of even the most compact galaxies in Virgo are larger than 150 pc ∼ 2'' (Ferrarese et al. 2006). Thus, a typical GC in Virgo can only be resolved at HST resolution, but a typical UCD can be resolved in high-quality ground-based images, like those from the NGVS. Note that the MegaCam pixel size is 0187, which corresponds to ∼15 pc at this distance.

In order to measure structural parameters—including half-light radii and total magnitudes—for the many thousands of GC candidates in the ACSVCS, Jordán et al. (2005) developed the KINGPHOT software package. Briefly, KINGPHOT fits—inside a fitting radius, r_fit—point-spread function (PSF)-convolved King (1966) models to each GC candidate and then determines structural parameters via χ² minimization. Needless to say, reliable PSF determination is essential for the successful application of this code. In the case of the ACSVCS, the KINGPHOT measurement limit on r_h was found to be ∼1 pc, which is about 1/8 of the instrumental PSF for ACS/WFC (FWHM ∼ 01). The uncertainty on r_h was also found to grow when r_h became comparable to r_fit.

In the present study, KINGPHOT has been adapted to measure the half-light radii for UCDs and bright GCs in the NGVS images. Not surprisingly, the main challenge in an application of KINGPHOT to ground-based images lies in the estimation of the PSF. Although the NGVS image quality is superb for a ground-based survey, the PSF is nevertheless much broader than that of HST (by about a factor of five in the i band). In addition, ground-based PSFs can change from field to field, and may vary significantly across an individual MegaCam pointing.

Complete details on the construction of PSFs in the NGVS will be presented in S. D. J. Gwyn et al. (2015, in preparation). Briefly, candidate PSF stars were first identified using SExtractor and DAOphot (only stars identified by both SExtractor and DAOphot were used). Additionally, stars within a distance of 40 pixels from other bright objects were discarded. The PSF was then generated using the DAOphot routine psf with a bivariate Gaussian and allowed to vary across the field with second order variations. In each NGVS field, the residual images for the PSF stars were checked to ensure there were no systematic trends with magnitude or position, and KINGPHOT was run only on bright point sources with high signal-to-noise ratios (S/N). Measurements in the g and i bands (which have the highest S/N and the best image quality) were made independently. Our final r_h values represent weighted averages of the measurements in the g and i bands.

For the catalog described in Section 2.2, a set of aperture magnitudes (within diameters of 3, 4, 5, 6, 7, 8, 16, and 32 pixels)²⁶ were measured for all objects. Because the PSFs differ from field to field, the magnitude within a given aperture does not represent the same percentage of total flux. Accordingly, we corrected the aperture magnitudes to infinite aperture in a two-stage process. First, a sample of bright (but unsaturated) stars were selected in each field and their 16-pixel aperture magnitudes corrected to infinity (calibrated to SDSS PSF magnitudes). Then, the other aperture magnitudes (3, 4, 5, 6, 7, and 8 pixels) were corrected to a 16-pixel aperture.

After the application of these corrections, we have a homogeneous database of point-source photometry across the entire NGVS survey area, all calibrated against the SDSS. This catalog also accounts for the small but measurable spatial variations in the PSF within individual fields, thereby tightening the stellar color–color and color–magnitude diagrams and aiding in the selection of targets (see, e.g., Figure 1 of Durrell et al. 2014). Figure 1 shows the aperture correction map made by stacking individual MegaCam pointings. The color coding highlights regions of negative and positive deviations in blue and red, respectively.

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It is important to determine the ranges in effective radius and magnitude over which the NGVS KINGPHOT measurements are reliable. We have addressed this question in several ways. First, we carried out a large number of simulations in which artificial sources were generated using PSF-convolved King models plus a realistic amount of noise. The simulated objects were then added randomly to NGVS images and their sizes measured using KINGPHOT. The artificial objects had g-band magnitudes in the range 20–23 mag, half-light radii between 1 and 100 pc, and concentration parameters, $c\equiv {\mathrm{log}}_{10}{r}_{t}/{r}_{c},$ between 0.5 and 2.3.²⁷ Figure 2 compares the actual and measured cluster sizes from these simulations; the symbols show mean values of Δ r_h/r_h while the errorbars show the standard deviation at each r_h. Results are shown, from top to bottom, in bins of decreasing magnitude (g = 20–23 mag). The KINGPHOT measurements are found to be in good agreement with the actual sizes over a wide range in radius, with the exception of the most compact objects which have input sizes of r_h ∼ 2 pc.

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The simulations show that there is a tendency to overestimate the sizes of the smallest objects and underestimate the sizes of the largest objects. The most reliable KINGPHOT measurements are obtained for objects brighter than g ∼ 21.5 mag and having half-light radii of r_h ∼ 30 pc. Of course, there are good reasons to expect that the measurements for the larger (r_h ≳ 50 pc) objects would show increased scatter. First, at fixed magnitude, larger objects always have lower mean surface brightness, and the lower S/N ratio will naturally lead to an enhanced scatter. Second, in our analysis the KINGPHOT fitting radius for the NGVS is 7 pixels. This corresponds to ≃105 pc at the distance of Virgo. Jordán et al. (2005) have shown that the KINGPHOT measurements begin to show a bias when r_h ≳ r_fit/2, which translates to ≳ 50 pc for the NGVS. As noted above, UCDs are often defined to have sizes between 10 and 100 pc, although the exact limits are arbitrary and several recent studies have found that most UCDs have 10 ≤ r_h ≤ 30 pc (Brodie et al. 2011; Chiboucas et al. 2011; Strader et al. 2011; Penny et al. 2012). Our choice of fitting radius thus seems appropriate for the majority of known UCDs. We conclude from the simulations that the KINGPHOT measurements should be reliable for UCDs and GCs brighter than g ≃ 21.5 and having half-light radii in the range ∼10–100 pc.

A second check on the reliability of the KINGPHOT sizes is possible using the independent g- and i-band measurements. We compare the measurements in these two bands in Figure 3, now showing only those objects with g ≤ 21.5 mag (see above). The dotted lines show sizes of 5, 10, 50, and 100 pc. The half-light radii are in good agreement over a wide range in radius—roughly from 5 to 100 pc. A third check on the NGVS size measurements is possible using regions of overlap between adjacent NGVS fields, where some sources can have their sizes measured in completely independent stacks. Figure 4 shows this comparison for the overlap regions in the four M87 fields. The agreement is once again very good, apart from the most compact objects. In fact, this comparison is likely to be overly pessimistic since the measurements in this case are made entirely at the edges of individual MegaCam fields where the image quality is poorest.

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Finally, we can compare our sizes with those measured from HST images. The blue squares in the upper panel of Figure 5 show the results of this comparison for GCs and UCDs from the ACSVCS (Haşegan et al. 2005; Jordán et al. 2005). Note that the NGVS sizes shown here refer to weighted mean sizes measured in the g and i bands. The agreement is quite good for objects with r_h ≳ 10 pc, although it is worth bearing in mind that the ACSVCS sizes were also made with KINGPHOT. The cyan squares in this figure show objects from Strader et al. (2011), who collected HST images and measured half-light radii for spectroscopically confirmed GCs and UCDs using the ISHAPE program of Larsen (1999). For the smallest objects (r_h ≲ 5 pc), the NGVS sizes are clearly overestimated, as expected from the simulations shown in Figure 2. For larger objects, the NGVS measurements generally compare favorably with the HST values, although there is a ∼25% downward offset for r_h ≳ 10 pc relative to the values of Strader et al. (2011). The explanation of this offset is unclear, and while it may be tempting to attribute the offset to the use of different algorithms (i.e., KINGPHOT versus ISHAPE), previous studies have shown the codes to yield fully compatible results (e.g., Peng et al. 2009), at least for GC-sized sources. In any case, our aim in this study is not to measure UCD sizes at a level of precision that rivals HST, but simply to identify any UCDs with sizes in the range ∼10–100 pc.

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After some experimentation, candidate UCDs identified on the basis of their magnitudes and colors (Section 2.4) were considered to have sizes appropriate for bonafide UCDs if three conditions were satisfied: (1) the measurement errors on r_h were less than 1.5 pc, in both the g and i bands; (2) the fractional difference in the size measurements was $| {r}_{h,g}-{r}_{h,i}| /$ $\langle {r}_{h}\rangle \leqslant 0.5;$ and (3) the weighted mean half-light radius was $\langle {r}_{h}\rangle \geqslant 11$ pc. Additionally, we limit our selection to sources brighter than g = 21.5 mag. Taken together, these criteria ensure that objects with uncertain sizes, spurious sources, and compact objects that may suffer from biased size measurements, are eliminated from our analysis. The lower panel of Figure 5 compares the g- and i-band sizes for candidate UCDs identified in our three program regions.

Before proceeding, we pause to explain the photometric measurements used in this analysis. For each UCD candidate, we have u*giz aperture magnitudes (and, in the M87 region, u*grizK_s), measured in a series of ever larger apertures as described above. We also have PSF-convolved King-model fits from KINGPHOT in the g and i bands. In principle, these latter values should provide the best photometry for the UCDs. However, there are two limitations with their use: (1) the KINGPHOT measurements are available only in two of the six bands; and (2) analogous measurements exist only for the brightest (g ≲ 21.5 mag) objects. For these reasons, in this paper we generally rely on the corrected, 16-pixel diameter aperture magnitudes when comparing the UCD and GC properties. In addition, aperture colors are most reliable when using relatively small apertures, so colors are based on measurements within an 8-pixel diameter aperture. Figure 6 compares the 16-pixel aperture and KINGPHOT magnitudes for our final sample of UCDs (see Section 2.6) in the M87 region, demonstrating that there is good agreement between the two sets of measurements.

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To select a sample of UCDs, we must rely on a combination of parameters: magnitudes, half-light radii, colors (specifically, their location within the color–color diagram or diagrams), and mean effective surface brightness. The magnitude range adopted for the selection of both UCDs and GCs in our study is 18.5 ≤ g ≤ 21.5 mag (−12.7 ≲ M_g ≲ −9.7). The bright limit is set by saturation in the NGVS long exposures while the faint limit reflects the minimum S/N needed to measure accurate sizes using KINGPHOT (see Section 2.3). Note that we select both UCD and GC candidates from their location in color–color diagrams (Sections 2.4.1 and 2.4.2) and identify UCDs on the basis of their larger sizes (11 ≤ r_h ≤ 100 pc, Section 2.3) and lower mean surface brightness at fixed luminosity (Section 2.4.2).

In this work, we aim to study the properties of UCDs around three luminous early-type galaxies in the Virgo cluster: M87 (=NGC 4486, VCC1316), M49 (=NGC 4472, VCC1226), and M60 (=NGC 4649, VCC1978). Some basic properties of these three galaxies are listed in Table 1, including coordinates, magnitudes, colors, effective radii, mean effective surface brightness, concentration c₈₂ (defined as the ratio of the radii containing 80% and 20% of the luminosity derived from a curve-of-growth analysis), stellar luminosity, stellar mass, X-ray gas mass, dark matter mass, VCC morphology, NGVS classification type, and other names.

Table 1.  Basic Data for M87, M49, and M60

Parameter	Units	M87	M49	M60	Referencesa
(1)	(2)	(3)	(4)	(5)	(6)
α(J2000)	degree	187.7059365	187.4448543	190.9165323	(1)
δ(J2000)	degree	+12.3911224	+8.0004889	+11.5527000	(1)
g	mag	9.03	8.71	9.11	(1)
$\langle (g-i)\rangle$	mag	1.15	1.12	1.10	(1)
Re	arcsec	96.3	105.7	76.0	(1)
${\langle {\mu }_{g}\rangle }_{e}$	mag arcsec−2	20.95	19.67	19.22	(1)
c82	⋯	10.06	9.85	9.71	(1)
${\mathrm{log}}_{10}[{L}_{g,\star }/{L}_{g,\odot }]$	⋯	10.92	11.04	10.89	(1)
${\mathrm{log}}_{10}[{M}_{\star }/{M}_{\odot }]$	⋯	11.55	11.63	11.46	(1)
${\mathrm{log}}_{10}[{M}_{\mathrm{gas}}/{M}_{\odot }]$	⋯	13.28	11.64	∼11	(3), (4)
${\mathrm{log}}_{10}[{M}_{\mathrm{DM}}/{M}_{\odot }]$	⋯	14.15	13.94	13.54	(3), (4)
VCC Morphology	⋯	E2/S01(2)	E0	S01(2)	(2)
NGVS Classification Type	⋯	E-Q	($\mathrm{Esh}| \mathrm{st}$)-Q	E(sh:)-Q	(1)
NGC	⋯	4486	4472	4649	⋯
VCC	⋯	1316	1226	1978	(2)

Note.

^aKey to references: (1) NGVS; (2) Binggeli et al. (1985), (3) Schindler et al. (1999), (4) Humphrey et al. (2006). All magnitudes and surface brightnesses have been extinction corrected and transposed to the SDSS photometric system. Luminosities and masses are calculated assuming the distance moduli listed in Mei et al. (2007).

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Although these are the three brightest galaxies in the cluster,²⁸ they occupy very different environments, as shown in Figure 7. As is well known, Virgo is not a dynamically relaxed system but consists of several distinct subclusters (e.g., Binggeli et al. 1987, 1993; Schindler et al. 1999; Mei et al. 2007). Subcluster A, which is centered on M87, is the dominant component of Virgo. Subcluster B, which is centered on M49 and located ∼4° to the south of M87, is considerably smaller and more compact than subcluster A (Binggeli et al. 1993). The third, less conspicuous, subcluster (C) is centered on a small group of galaxies containing M59 and M60 located ∼3° to the east of M87 (Binggeli et al. 1987).²⁹ Similarly, X-ray imaging of the cluster shows some dramatic differences in the properties of the hot gas in the vicinity of these galaxies (Böhringer et al. 1994). Located at the center of subcluster A, M87 is unsurprisingly embedded in a vast, massive reservoir of X-ray-emitting gas. M49 contains much less (∼1/40) hot gas than M87, but substantially more than M60 (4–5×).

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These three galaxies also reside in quite different environments in terms of their surrounding diffuse light. Located at the cluster center, M87 possesses an extended diffuse envelope and is embedded in a web of intracluster light (Castro-Rodriguéz et al. 2009; Mihos et al. 2009; Rudick et al. 2010). However, this web is highly concentrated in the central regions of Virgo (Castro-Rodriguéz et al. 2009; Boselli et al. 2014, J. C. Mihos et al. 2015, in preparation). Rather than being embedded in an extended envelope of diffuse light, M49 shows tidal features scattered througout its halo (Janowiecki et al. 2010; Arrigoni Battaia et al. 2012; Ferrarese et al. 2012), while M60 shows diffuse light associated with M59 (Yan et al. 2008). These differences in the prominence and morphology the diffuse light surrounding each galaxy are likely related to the different dynamical histories of the three regions.

2.4.1. u*iK_s Selection

In the NGVS pilot program region (the four fields in the immediate vicinity of M87: NGVS+0+0, NGVS+0+1, NGVS-1+0 and NGVS-1+1), we have imaging in all five optical bands, u*griz (Ferrarese et al. 2012), plus K_s-band imaging from the NGVS-IR (Muñoz et al. 2014). In this region, we are thus able to select UCD and GC candidates directly from the (${u}^{*}-i$)-(i − K_s) color–color diagram (=u*iK_s) which was shown by Muñoz et al. (2014) to be remarkably effective in separating UCDs and GCs from foreground stars and background galaxies. Indeed, Figure 8 shows that the sources in the M87 region—many of which have been observed spectroscopically (see Zhu et al. 2014; Zhang et al. 2015)—can be neatly separated into three main groups in the u*iK_s diagram: GCs and UCDs, background galaxies, and foreground stars. The polygon in this figure shows our adopted selection region for UCDs and GCs, a region that includes all of the spectroscopically confirmed UCDs and most of the confirmed GCs in the vicinity of M87 (Hanes et al. 2001; Strader et al. 2011; Zhang et al. 2015).

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2.4.2. u*gz Selection

Unfortunately, of the 117 MegaCam fields that make up the NGVS, a K_s-band photometric catalog is available at this time in only the four pilot program fields. For the remaining fields, including the M49 and M60 regions, we must rely on the (${u}^{*}-g$)-(g − z) color–color diagram (=u*gz) to identify UCD and GC candidates. While there is certainly a separation of UCDs and GCs from foreground stars and background galaxies in this color–color space, it is not as dramatic as in the case of u*iK_s (Muñoz et al. 2014). As Figure 9 demonstrates, the sample of u*gz-selected UCD and GC candidates (blue and cyan dots) shows some overlap with the regions occupied by spectroscopically confirmed stars and galaxies (green and orange dots). As the previous figure, the polygon in Figure 9 shows our adopted selection region for UCDs and GCs.

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To better understand contamination arising from the selection of UCDs and GCs in the u*gz diagram, we show in Figure 10 the distribution of u*gz-selected candidates from the M87 region in the u*iK_s diagram (red dots). For comparison, the complete sample of sources in this region is shown by the faint gray dots. Clearly, the level of contamination is non-negligible, with many of the u*gz-selected UCD and GCs candidates located in the regions occupied by stars or galaxies.

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To reduce the contamination in this u*gz-selected sample, we impose an additional selection on mean effective surface brightness, $\langle {\mu }_{g}{\rangle }_{e}.$ In the upper panel of Figure 11, the spectroscopically confirmed UCDs and GCs are found to occupy a relatively narrow range in surface brightness (dashed histogram). The lower panel of Figure 11 shows mean effective surface brightness plotted against (g − i) color for all u*gz- and u*iK_s-selected sources from the M87 region (gray and black dots, respectively). Spectroscopically confirmed UCDs, GCs, and galaxies are shown by the blue, cyan and orange symbols, as indicated in the legend. The irregular pentagon (denoted by the dotted lines) shows the region of $\langle {\mu }_{g}{\rangle }_{e}$-(g − i) space used to identify UCDs and GCs; the diagonal boundary in the upper right corner was used to minimize contamination from background galaxies, which tend to have red colors and low surface brightness. While a selection on surface brightness does mean that a small number of (high surface brightness) GCs will be missed, all but four of the spectroscopically confirmed UCDs are identified using this approach.

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Figure 10 plots the u*gz and surface brightness-selected objects in the u*iK_s diagram as blue dots. Although a handful of objects are still found in the regions of the diagram occupied by stars or galaxies, the sample is clearly much cleaner than before. We notice that the u*iK_s-selection does introduce many background galaxies, as seen in the lower panel of Figure 11 (the cloud of black points in the upper right corner). Therefore, we proceed by selecting UCD candidates relying on a combination of u*iK_s and $\langle {\mu }_{g}{\rangle }_{e}$-(g − i) diagram for the M87 region, and a combination of u*gz and $\langle {\mu }_{g}{\rangle }_{e}$-(g − i) diagrams for M49 and M60 regions.

2.4.3. Visual Inspection of UCD Candidates

After the color–color selection, the UCD candidates in all three regions (M87, M49 and M60) were separated from GCs on the basis of their half-light radii. Operationally, the UCDs were defined as those objects with r_h > 11 pc (Section 2.3; see also Drinkwater et al. 2004; Brüns and Kroupa 2012; Penny et al. 2012; Willman & Strader 2012) and M_g < −9.7 mag. Up to this point, UCD selection was performed in a completely objective manner. However, a final, somewhat subjective step—a visual inspection of each candidate—is required to eliminate obvious contaminants or artifacts. Such contaminants were usually found to be nucleated dwarf galaxies or compact background galaxies. After a visual inspection, each candidate was assigned a classification code to identify it as a UCD or an another type of object: (1) = probable UCD; (2) = dwarf nucleus; (3) = background galaxy; (4) = other type of contaminant (usually a candidate UCD with uncertain properties due to its being located close to a bright star, stellar halo, or CCD bleed trail).

Figures 12–16 present g-band mosaics for our complete, objectively selected sample of candidate UCDs in the M87 region. Each panel has been labelled with both our class parameter and the object identification number from Tables 2 and 3. These 127 objects make up our sample of UCD candidates that satisfy the joint selection criteria on magnitude, color and size described above.

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Table 2.  Photometric Properties of UCD Candidates in the M87 Region

ID	NGVSID	αJ2000	δJ2000	$E(B-V)$	g16	${({u}^{*}-g)}_{8}$	${(g-r)}_{8}$	${(g-i)}_{8}$	${(g-z)}_{8}$	${(g-{K}_{s})}_{8}$	Δenv	UCD
		(degree)	(degree)	(mag)	(mag)	(mag)	(mag)	(mag)	(mag)	(mag)	(mag)
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)	(12)	(13)
1	NGVS-J122623.21+121925.2	186.5966882	12.3236728	0.027	19.603 ± 0.001	0.910 ± 0.003	0.435 ± 0.002	0.728 ± 0.002	0.840 ± 0.003	1.231 ± 0.003	0.061	0
2	NGVS-J122628.69+125642.6	186.6195415	12.9451739	0.029	19.695 ± 0.001	1.312 ± 0.003	0.616 ± 0.002	0.920 ± 0.002	1.120 ± 0.003	1.145 ± 0.004	0.064	1
3	NGVS-J122633.05+123847.6	186.6377219	12.6465456	0.032	21.303 ± 0.003	1.009 ± 0.008	0.482 ± 0.005	0.728 ± 0.006	0.808 ± 0.009	0.596 ± 0.015	0.006	0
4	NGVS-J122636.42+125512.9	186.6517616	12.9202470	0.028	18.947 ± 0.001	1.354 ± 0.002	0.622 ± 0.001	0.944 ± 0.001	1.152 ± 0.002	1.226 ± 0.002	0.000	1
5	NGVS-J122638.52+123702.7	186.6604821	12.6174078	0.032	20.575 ± 0.002	1.041 ± 0.005	0.498 ± 0.003	0.753 ± 0.004	0.825 ± 0.005	0.617 ± 0.009	−0.004	1
6	NGVS-J122638.79+124545.8	186.6616360	12.7627110	0.030	20.520 ± 0.002	1.029 ± 0.005	0.498 ± 0.003	0.750 ± 0.004	0.886 ± 0.005	0.632 ± 0.007	0.010	1
7	NGVS-J122643.32+121743.9	186.6804595	12.2955414	0.027	20.750 ± 0.002	0.985 ± 0.007	0.517 ± 0.003	0.723 ± 0.004	0.907 ± 0.007	0.490 ± 0.012	0.079	0
8	NGVS-J122646.48+131732.2	186.6936696	13.2922923	0.027	21.395 ± 0.003	0.936 ± 0.008	0.467 ± 0.005	0.727 ± 0.006	0.788 ± 0.009	1.203 ± 0.013	−0.006	0
9	NGVS-J122647.07+122714.0	186.6961017	12.4538766	0.030	19.541 ± 0.001	1.122 ± 0.004	0.631 ± 0.002	0.964 ± 0.002	1.108 ± 0.003	0.981 ± 0.004	0.406	0
10	NGVS-J122649.87+115931.8	186.7077996	11.9921620	0.025	21.487 ± 0.003	1.103 ± 0.011	0.487 ± 0.005	0.767 ± 0.007	0.902 ± 0.011	1.081 ± 0.013	0.018	0
11	NGVS-J122656.56+123532.2	186.7356434	12.5922742	0.031	19.801 ± 0.001	1.123 ± 0.003	0.576 ± 0.002	0.846 ± 0.002	0.992 ± 0.003	0.877 ± 0.004	0.077	1
12	NGVS-J122708.43+132009.0	186.7850984	13.3358383	0.026	21.365 ± 0.004	1.011 ± 0.012	0.509 ± 0.007	0.755 ± 0.009	0.906 ± 0.012	0.678 ± 0.022	0.283	0
13	NGVS-J122726.54+131150.7	186.8605838	13.1974160	0.031	20.907 ± 0.003	0.965 ± 0.007	0.441 ± 0.005	0.767 ± 0.007	0.851 ± 0.008	0.912 ± 0.011	0.028	0
14	NGVS-J122727.19+125546.0	186.8632841	12.9294426	0.028	21.012 ± 0.002	0.958 ± 0.006	0.478 ± 0.004	0.718 ± 0.005	0.804 ± 0.007	0.550 ± 0.014	−0.027	1
15	NGVS-J122729.00+131903.4	186.8708425	13.3176108	0.026	21.322 ± 0.003	1.112 ± 0.009	0.547 ± 0.005	0.883 ± 0.006	1.047 ± 0.008	1.296 ± 0.011	0.097	0
16	NGVS-J122745.56+124356.4	186.9398394	12.7323291	0.029	21.526 ± 0.003	1.080 ± 0.010	0.501 ± 0.005	0.744 ± 0.007	0.850 ± 0.010	0.692 ± 0.015	0.010	0
17	NGVS-J122804.51+121507.6	187.0187896	12.2521076	0.027	21.378 ± 0.005	1.017 ± 0.017	0.469 ± 0.009	0.751 ± 0.010	0.764 ± 0.019	1.201 ± 0.012	0.071	0
18	NGVS-J122806.62+122436.4	187.0275966	12.4101100	0.028	20.941 ± 0.002	1.022 ± 0.007	0.521 ± 0.004	0.721 ± 0.005	0.828 ± 0.008	0.629 ± 0.009	0.018	0
19	NGVS-J122837.21+122845.6	187.1550495	12.4793425	0.024	21.014 ± 0.002	1.045 ± 0.007	0.530 ± 0.004	0.747 ± 0.005	0.885 ± 0.007	0.680 ± 0.014	0.014	1
20	NGVS-J122856.90+130220.5	187.2370664	13.0390265	0.022	21.342 ± 0.004	0.953 ± 0.010	0.514 ± 0.006	0.725 ± 0.008	0.855 ± 0.012	0.588 ± 0.016	0.084	1
21	NGVS-J122910.66+124304.1	187.2944290	12.7178146	0.022	20.883 ± 0.002	1.127 ± 0.008	0.632 ± 0.004	0.818 ± 0.004	0.918 ± 0.008	0.883 ± 0.007	0.005	1
22	NGVS-J122914.82+113622.4	187.3117572	11.6062340	0.034	21.220 ± 0.003	0.893 ± 0.008	0.404 ± 0.005	0.723 ± 0.006	0.918 ± 0.009	1.372 ± 0.007	−0.007	0
23	NGVS-J122914.87+115343.8	187.3119410	11.8955165	0.027	20.189 ± 0.001	1.047 ± 0.004	0.539 ± 0.002	0.790 ± 0.003	0.925 ± 0.004	0.753 ± 0.004	0.058	1
24	NGVS-J122925.49+121835.8	187.3562019	12.3099218	0.024	20.838 ± 0.003	1.135 ± 0.009	0.476 ± 0.004	0.756 ± 0.006	0.880 ± 0.008	1.039 ± 0.008	0.041	0
25	NGVS-J122936.29+113708.5	187.4011880	11.6190412	0.036	21.057 ± 0.002	1.169 ± 0.008	0.516 ± 0.004	0.799 ± 0.005	0.989 ± 0.007	1.345 ± 0.007	0.014	0
26	NGVS-J122937.04+130620.9	187.4043319	13.1058181	0.022	20.988 ± 0.002	0.945 ± 0.006	0.383 ± 0.004	0.654 ± 0.005	0.753 ± 0.008	0.931 ± 0.011	0.034	0
27	NGVS-J122937.93+114058.1	187.4080229	11.6828173	0.035	21.198 ± 0.003	1.005 ± 0.008	0.506 ± 0.004	0.718 ± 0.005	0.924 ± 0.008	0.715 ± 0.012	0.006	1
28	NGVS-J122940.39+122728.1	187.4182872	12.4577958	0.023	19.958 ± 0.001	1.112 ± 0.004	0.515 ± 0.002	0.775 ± 0.002	0.849 ± 0.003	0.644 ± 0.005	0.017	1
29	NGVS-J122941.32+123952.4	187.4221790	12.6645688	0.021	20.255 ± 0.002	1.161 ± 0.005	0.509 ± 0.003	0.791 ± 0.004	0.971 ± 0.004	0.820 ± 0.006	0.049	1
30	NGVS-J122941.56+124427.6	187.4231465	12.7410002	0.022	20.948 ± 0.002	1.179 ± 0.007	0.584 ± 0.004	0.848 ± 0.004	1.012 ± 0.006	0.930 ± 0.008	−0.020	1
31	NGVS-J122942.29+131727.6	187.4261812	13.2910772	0.026	19.680 ± 0.001	1.633 ± 0.004	0.764 ± 0.002	1.068 ± 0.002	1.287 ± 0.002	1.732 ± 0.003	0.235	0
32	NGVS-J122945.26+125100.9	187.4385733	12.8502553	0.020	20.508 ± 0.002	1.095 ± 0.005	0.537 ± 0.003	0.768 ± 0.003	0.894 ± 0.005	0.794 ± 0.008	0.007	1
33	NGVS-J122947.20+121717.8	187.4466393	12.2882768	0.025	19.679 ± 0.001	1.033 ± 0.004	0.443 ± 0.002	0.725 ± 0.002	0.834 ± 0.003	1.236 ± 0.003	0.180	0
34	NGVS-J122950.93+123653.2	187.4621952	12.6147895	0.021	21.429 ± 0.004	1.063 ± 0.010	0.460 ± 0.006	0.696 ± 0.008	0.851 ± 0.011	0.636 ± 0.017	−0.022	0
35	NGVS-J122952.28+123737.8	187.4678260	12.6271638	0.021	20.803 ± 0.002	1.275 ± 0.007	0.626 ± 0.003	0.873 ± 0.004	1.099 ± 0.006	1.087 ± 0.007	0.006	1
36	NGVS-J122952.41+123504.1	187.4683715	12.5844700	0.022	19.746 ± 0.001	1.055 ± 0.004	0.491 ± 0.002	0.692 ± 0.003	0.902 ± 0.003	0.662 ± 0.004	0.070	1
37	NGVS-J122954.98+123350.9	187.4790895	12.5641282	0.022	20.617 ± 0.002	1.003 ± 0.005	0.484 ± 0.003	0.703 ± 0.004	0.862 ± 0.006	0.615 ± 0.008	0.043	1
38	NGVS-J122956.35+131312.1	187.4847166	13.2200542	0.024	20.002 ± 0.001	1.018 ± 0.004	0.575 ± 0.002	0.751 ± 0.003	0.798 ± 0.004	0.591 ± 0.008	0.135	0
39	NGVS-J122957.12+123602.9	187.4880095	12.6008171	0.022	20.266 ± 0.001	0.997 ± 0.004	0.474 ± 0.002	0.719 ± 0.003	0.866 ± 0.004	0.590 ± 0.006	−0.021	1
40	NGVS-J123001.95+124226.9	187.5081185	12.7074667	0.022	19.865 ± 0.001	0.937 ± 0.005	0.487 ± 0.002	0.713 ± 0.003	0.750 ± 0.004	0.533 ± 0.005	0.038	1
41	NGVS-J123002.46+123633.8	187.5102296	12.6093775	0.022	20.208 ± 0.001	1.125 ± 0.005	0.528 ± 0.002	0.790 ± 0.003	0.956 ± 0.004	0.842 ± 0.005	−0.010	1
42	NGVS-J123004.05+120714.0	187.5168687	12.1205496	0.028	19.732 ± 0.001	1.085 ± 0.003	0.533 ± 0.002	0.795 ± 0.002	0.878 ± 0.003	0.648 ± 0.003	0.008	1
43	NGVS-J123006.06+123954.0	187.5252451	12.6649930	0.021	19.479 ± 0.001	1.171 ± 0.003	0.516 ± 0.002	0.792 ± 0.002	0.987 ± 0.002	0.901 ± 0.003	−0.017	1
44	NGVS-J123006.13+122435.3	187.5255256	12.4098184	0.026	20.594 ± 0.002	1.208 ± 0.006	0.544 ± 0.003	0.849 ± 0.003	0.944 ± 0.005	0.910 ± 0.006	−0.023	1
45	NGVS-J123007.57+123631.0	187.5315491	12.6086113	0.022	19.052 ± 0.001	1.213 ± 0.002	0.551 ± 0.001	0.843 ± 0.001	1.027 ± 0.002	1.006 ± 0.002	0.003	1
46	NGVS-J123009.82+123736.5	187.5409141	12.6267936	0.022	21.041 ± 0.002	1.090 ± 0.007	0.520 ± 0.004	0.784 ± 0.005	0.925 ± 0.007	0.815 ± 0.011	−0.025	1
47	NGVS-J123010.00+123604.7	187.5416814	12.6012962	0.022	21.497 ± 0.003	1.062 ± 0.010	0.491 ± 0.006	0.741 ± 0.007	0.911 ± 0.010	0.690 ± 0.018	−0.048	1
48	NGVS-J123010.89+121143.7	187.5453605	12.1954912	0.025	21.038 ± 0.002	1.025 ± 0.008	0.476 ± 0.004	0.725 ± 0.005	0.760 ± 0.009	0.535 ± 0.013	0.284	0
49	NGVS-J123011.07+124721.7	187.5461272	12.7893612	0.022	20.576 ± 0.002	1.127 ± 0.005	0.519 ± 0.003	0.792 ± 0.003	0.948 ± 0.005	0.784 ± 0.007	0.023	1
50	NGVS-J123014.74+120726.5	187.5614188	12.1240380	0.028	21.253 ± 0.003	0.939 ± 0.008	0.378 ± 0.004	0.660 ± 0.006	0.736 ± 0.010	0.803 ± 0.011	−0.019	0
51	NGVS-J123016.54+121556.8	187.5689170	12.2657885	0.023	20.037 ± 0.001	1.015 ± 0.005	0.431 ± 0.003	0.735 ± 0.003	0.899 ± 0.004	0.632 ± 0.004	0.081	1
52	NGVS-J123017.80+114447.4	187.5741725	11.7465080	0.033	19.136 ± 0.001	1.474 ± 0.004	0.765 ± 0.001	0.988 ± 0.002	1.255 ± 0.002	1.594 ± 0.001	0.146	0
53	NGVS-J123019.63+120924.6	187.5818070	12.1568307	0.027	21.079 ± 0.002	1.065 ± 0.007	0.492 ± 0.004	0.705 ± 0.004	0.818 ± 0.006	0.527 ± 0.009	0.004	1
54	NGVS-J123020.05+115518.7	187.5835090	11.9218754	0.030	19.343 ± 0.001	1.099 ± 0.003	0.582 ± 0.001	0.814 ± 0.002	0.999 ± 0.002	0.842 ± 0.003	0.120	1
55	NGVS-J123021.83+122402.4	187.5909557	12.4006720	0.023	19.932 ± 0.001	1.404 ± 0.004	0.626 ± 0.002	0.958 ± 0.002	1.175 ± 0.002	1.296 ± 0.002	0.024	1
56	NGVS-J123022.97+123148.7	187.5957005	12.5302086	0.022	19.753 ± 0.001	1.079 ± 0.003	0.521 ± 0.002	0.767 ± 0.002	0.863 ± 0.003	0.706 ± 0.005	0.099	1
57	NGVS-J123025.75+122621.1	187.6073036	12.4391949	0.022	20.461 ± 0.001	1.079 ± 0.005	0.516 ± 0.002	0.756 ± 0.003	0.883 ± 0.004	0.727 ± 0.005	0.004	1
58	NGVS-J123026.56+122044.6	187.6106637	12.3457239	0.023	20.376 ± 0.001	1.089 ± 0.005	0.593 ± 0.002	0.750 ± 0.003	0.875 ± 0.004	0.699 ± 0.004	−0.019	1
59	NGVS-J123026.89+122331.1	187.6120793	12.3919745	0.022	19.928 ± 0.001	1.155 ± 0.004	0.596 ± 0.002	0.801 ± 0.002	0.940 ± 0.003	0.854 ± 0.003	0.012	1
60	NGVS-J123029.91+123822.2	187.6246350	12.6394879	0.021	20.466 ± 0.002	0.927 ± 0.005	0.466 ± 0.002	0.680 ± 0.003	0.766 ± 0.005	0.464 ± 0.013	0.023	1
61	NGVS-J123030.86+121841.7	187.6285824	12.3115772	0.023	19.735 ± 0.001	1.131 ± 0.003	0.556 ± 0.002	0.794 ± 0.002	0.962 ± 0.002	0.834 ± 0.003	0.077	1
62	NGVS-J123031.44+125156.6	187.6310053	12.8657287	0.021	20.133 ± 0.001	1.347 ± 0.005	0.644 ± 0.002	0.956 ± 0.002	1.148 ± 0.003	1.303 ± 0.004	0.102	1
63	NGVS-J123031.53+122602.6	187.6313759	12.4340546	0.022	20.296 ± 0.001	0.987 ± 0.004	0.570 ± 0.002	0.717 ± 0.003	0.835 ± 0.004	0.521 ± 0.005	0.003	1
64	NGVS-J123033.43+122954.3	187.6392871	12.4984422	0.021	19.236 ± 0.001	1.120 ± 0.003	0.543 ± 0.001	0.793 ± 0.002	0.932 ± 0.002	0.825 ± 0.003	0.141	1
65	NGVS-J123034.12+122246.5	187.6421756	12.3795711	0.022	21.333 ± 0.003	1.043 ± 0.009	0.517 ± 0.004	0.741 ± 0.006	0.869 ± 0.008	0.605 ± 0.011	−0.017	1
66	NGVS-J123035.02+123452.7	187.6459060	12.5813054	0.021	20.506 ± 0.002	1.035 ± 0.006	0.513 ± 0.003	0.754 ± 0.004	0.876 ± 0.005	0.708 ± 0.012	0.140	1
67	NGVS-J123036.52+122152.8	187.6521566	12.3646753	0.023	20.549 ± 0.002	1.081 ± 0.007	0.554 ± 0.003	0.760 ± 0.004	0.922 ± 0.005	0.676 ± 0.005	−0.003	1
68	NGVS-J123039.16+122132.5	187.6631525	12.3590152	0.023	20.717 ± 0.002	1.016 ± 0.007	0.603 ± 0.004	0.796 ± 0.004	0.988 ± 0.006	0.745 ± 0.007	0.035	1
69	NGVS-J123041.81+122341.2	187.6742275	12.3947905	0.023	21.180 ± 0.003	1.000 ± 0.009	0.489 ± 0.005	0.751 ± 0.006	0.868 ± 0.008	0.604 ± 0.010	0.001	1
70	NGVS-J123043.25+122212.4	187.6802149	12.3701094	0.023	21.207 ± 0.003	1.068 ± 0.010	0.479 ± 0.005	0.789 ± 0.006	0.935 ± 0.008	0.756 ± 0.009	0.009	1
71	NGVS-J123045.34+122033.5	187.6889027	12.3426310	0.024	20.679 ± 0.002	1.020 ± 0.007	0.528 ± 0.004	0.773 ± 0.004	0.919 ± 0.006	0.672 ± 0.007	0.022	1
72	NGVS-J123045.95+113752.5	187.6914326	11.6312694	0.040	21.157 ± 0.002	1.010 ± 0.009	0.420 ± 0.004	0.717 ± 0.005	0.850 ± 0.008	1.169 ± 0.010	0.150	0
73	NGVS-J123046.50+122017.7	187.6937513	12.3382606	0.024	20.786 ± 0.002	1.014 ± 0.007	0.527 ± 0.004	0.770 ± 0.004	0.921 ± 0.006	0.698 ± 0.008	0.034	1
74	NGVS-J123047.40+123301.7	187.6974884	12.5504714	0.021	19.463 ± 0.001	1.204 ± 0.003	0.606 ± 0.001	0.907 ± 0.002	1.082 ± 0.002	1.123 ± 0.003	0.067	1
75	NGVS-J123047.66+120825.2	187.6985647	12.1403408	0.026	19.732 ± 0.001	1.036 ± 0.003	0.486 ± 0.002	0.682 ± 0.002	0.847 ± 0.003	0.556 ± 0.003	0.041	1
76	NGVS-J123047.70+122430.5	187.6987573	12.4084661	0.023	19.779 ± 0.001	1.010 ± 0.004	0.517 ± 0.002	0.765 ± 0.003	0.906 ± 0.003	0.687 ± 0.004	0.019	1
77	NGVS-J123048.19+123510.7	187.7008418	12.5863658	0.021	19.135 ± 0.001	1.130 ± 0.003	0.560 ± 0.001	0.827 ± 0.001	0.971 ± 0.002	0.875 ± 0.003	0.065	1
78	NGVS-J123049.28+123718.2	187.7053422	12.6217134	0.021	19.951 ± 0.001	1.103 ± 0.004	0.563 ± 0.002	0.820 ± 0.002	0.946 ± 0.003	0.808 ± 0.007	0.016	1
79	NGVS-J123049.49+121426.9	187.7062251	12.2408141	0.024	20.574 ± 0.002	1.156 ± 0.007	0.595 ± 0.003	0.747 ± 0.004	0.916 ± 0.006	0.740 ± 0.007	0.015	1
80	NGVS-J123051.07+122611.9	187.7127756	12.4366444	0.022	19.674 ± 0.001	1.271 ± 0.004	0.604 ± 0.002	0.915 ± 0.002	1.124 ± 0.002	1.181 ± 0.002	0.006	1
81	NGVS-J123051.65+121409.9	187.7152156	12.2360794	0.024	21.050 ± 0.003	1.058 ± 0.009	0.550 ± 0.004	0.669 ± 0.005	0.826 ± 0.007	0.513 ± 0.011	0.022	1
82	NGVS-J123051.75+122053.3	187.7156252	12.3481400	0.024	20.806 ± 0.002	1.041 ± 0.007	0.517 ± 0.004	0.764 ± 0.004	0.898 ± 0.006	0.649 ± 0.007	−0.022	1
83	NGVS-J123053.88+121712.4	187.7245095	12.2867885	0.024	21.104 ± 0.003	1.146 ± 0.010	0.503 ± 0.005	0.861 ± 0.005	1.019 ± 0.008	0.888 ± 0.009	0.010	1
84	NGVS-J123054.66+122022.6	187.7277335	12.3396047	0.024	21.301 ± 0.003	0.913 ± 0.009	0.479 ± 0.005	0.706 ± 0.006	0.822 ± 0.009	0.389 ± 0.015	−0.005	1
85	NGVS-J123101.47+121924.5	187.7561416	12.3234824	0.023	19.654 ± 0.001	1.343 ± 0.004	0.626 ± 0.002	0.958 ± 0.002	1.171 ± 0.002	1.203 ± 0.002	−0.009	1
86	NGVS-J123102.14+122749.7	187.7589066	12.4638040	0.021	20.648 ± 0.002	0.943 ± 0.006	0.492 ± 0.003	0.738 ± 0.004	0.865 ± 0.005	0.528 ± 0.008	0.023	1
87	NGVS-J123102.59+123414.1	187.7607769	12.5705885	0.021	19.793 ± 0.001	0.962 ± 0.004	0.515 ± 0.002	0.745 ± 0.002	0.848 ± 0.003	0.574 ± 0.006	0.043	1
88	NGVS-J123103.69+123213.0	187.7653609	12.5369543	0.020	20.012 ± 0.001	0.996 ± 0.005	0.504 ± 0.002	0.758 ± 0.003	0.852 ± 0.004	0.637 ± 0.007	0.031	1
89	NGVS-J123104.35+131042.5	187.7681395	13.1784863	0.025	20.265 ± 0.002	1.349 ± 0.008	0.594 ± 0.003	0.946 ± 0.003	1.157 ± 0.004	1.185 ± 0.008	0.015	1
90	NGVS-J123104.43+122321.2	187.7684426	12.3892326	0.023	20.670 ± 0.002	0.974 ± 0.007	0.471 ± 0.004	0.722 ± 0.005	0.861 ± 0.007	0.569 ± 0.008	0.041	1
91	NGVS-J123104.80+131436.6	187.7699768	13.2435029	0.026	20.640 ± 0.002	1.062 ± 0.007	0.521 ± 0.003	0.723 ± 0.004	0.880 ± 0.007	0.536 ± 0.015	0.104	1
92	NGVS-J123110.14+121627.9	187.7922721	12.2744269	0.022	21.207 ± 0.003	1.096 ± 0.012	0.509 ± 0.005	0.834 ± 0.006	0.981 ± 0.009	0.768 ± 0.010	0.005	1
93	NGVS-J123110.42+130550.4	187.7933990	13.0973410	0.023	20.760 ± 0.002	1.006 ± 0.007	0.515 ± 0.003	0.747 ± 0.004	0.866 ± 0.006	0.592 ± 0.011	0.189	0
94	NGVS-J123111.31+123001.0	187.7971024	12.5002931	0.020	20.759 ± 0.002	1.231 ± 0.007	0.581 ± 0.003	0.872 ± 0.004	1.028 ± 0.005	0.972 ± 0.010	0.073	1
95	NGVS-J123116.32+121845.4	187.8180104	12.3126096	0.022	20.940 ± 0.002	1.067 ± 0.007	0.539 ± 0.003	0.810 ± 0.004	0.947 ± 0.006	0.799 ± 0.007	0.018	1
96	NGVS-J123120.00+121158.1	187.8333318	12.1994729	0.023	20.482 ± 0.001	1.131 ± 0.005	0.504 ± 0.002	0.771 ± 0.003	0.904 ± 0.004	0.699 ± 0.005	0.004	1
97	NGVS-J123124.75+122525.8	187.8531412	12.4238373	0.022	19.799 ± 0.001	1.051 ± 0.003	0.539 ± 0.002	0.774 ± 0.002	0.917 ± 0.002	0.709 ± 0.003	0.007	1
98	NGVS-J123125.25+121931.8	187.8551910	12.3254925	0.023	20.225 ± 0.001	0.970 ± 0.004	0.513 ± 0.002	0.753 ± 0.003	0.873 ± 0.004	0.576 ± 0.004	0.046	1
99	NGVS-J123128.36+122503.6	187.8681630	12.4176659	0.023	19.322 ± 0.001	1.139 ± 0.002	0.572 ± 0.001	0.818 ± 0.001	0.992 ± 0.002	0.869 ± 0.002	0.082	1
100	NGVS-J123131.70+113610.7	187.8819752	11.6030553	0.046	21.024 ± 0.003	1.085 ± 0.009	0.438 ± 0.005	0.792 ± 0.006	0.971 ± 0.008	0.700 ± 0.011	0.311	0
101	NGVS-J123131.70+124130.4	187.8820942	12.6917714	0.025	19.494 ± 0.002	1.068 ± 0.006	0.623 ± 0.003	0.895 ± 0.004	1.142 ± 0.004	0.913 ± 0.004	0.138	1
102	NGVS-J123135.13+123459.4	187.8963932	12.5831576	0.024	20.097 ± 0.001	1.266 ± 0.005	0.616 ± 0.002	0.906 ± 0.002	1.108 ± 0.003	1.089 ± 0.004	0.064	1
103	NGVS-J123137.44+121740.7	187.9059957	12.2946473	0.023	20.599 ± 0.002	0.981 ± 0.005	0.417 ± 0.003	0.731 ± 0.004	0.850 ± 0.005	0.559 ± 0.006	0.007	1
104	NGVS-J123138.53+115923.9	187.9105228	11.9899637	0.029	20.776 ± 0.002	1.108 ± 0.007	0.505 ± 0.003	0.772 ± 0.004	0.892 ± 0.005	0.687 ± 0.007	0.005	1
105	NGVS-J123145.95+122721.1	187.9414762	12.4558597	0.025	21.342 ± 0.003	0.949 ± 0.008	0.479 ± 0.004	0.698 ± 0.005	0.832 ± 0.008	0.568 ± 0.014	0.031	1
106	NGVS-J123151.34+123925.2	187.9639128	12.6569877	0.026	19.880 ± 0.001	1.074 ± 0.005	0.535 ± 0.002	0.821 ± 0.003	0.987 ± 0.004	0.783 ± 0.006	0.304	0
107	NGVS-J123152.96+115052.9	187.9706653	11.8480245	0.032	20.874 ± 0.002	1.047 ± 0.007	0.567 ± 0.003	0.860 ± 0.004	1.017 ± 0.006	1.532 ± 0.005	0.012	0
108	NGVS-J123157.60+124929.6	187.9899987	12.8248810	0.023	20.315 ± 0.001	1.045 ± 0.006	0.498 ± 0.002	0.767 ± 0.003	0.832 ± 0.005	0.601 ± 0.007	0.021	1
109	NGVS-J123157.99+131534.1	187.9916397	13.2594794	0.027	19.657 ± 0.001	0.973 ± 0.004	0.535 ± 0.002	0.755 ± 0.003	0.885 ± 0.003	0.572 ± 0.007	0.084	1
110	NGVS-J123204.35+122030.3	188.0181367	12.3417639	0.026	19.642 ± 0.001	1.107 ± 0.003	0.566 ± 0.001	0.826 ± 0.002	0.956 ± 0.002	0.862 ± 0.003	0.071	1
111	NGVS-J123211.80+113818.6	188.0491434	11.6384938	0.040	19.829 ± 0.001	0.919 ± 0.003	0.441 ± 0.002	0.746 ± 0.002	0.818 ± 0.003	1.234 ± 0.003	0.064	0
112	NGVS-J123214.45+120159.0	188.0602008	12.0330727	0.029	20.650 ± 0.002	1.159 ± 0.006	0.571 ± 0.003	0.864 ± 0.003	1.016 ± 0.005	0.932 ± 0.006	0.076	1
113	NGVS-J123214.58+120305.3	188.0607390	12.0514896	0.029	19.446 ± 0.001	1.214 ± 0.003	0.562 ± 0.001	0.881 ± 0.002	1.022 ± 0.002	0.974 ± 0.002	0.079	1
114	NGVS-J123221.10+121613.4	188.0879280	12.2703999	0.027	20.773 ± 0.002	0.986 ± 0.008	0.442 ± 0.004	0.791 ± 0.005	0.924 ± 0.007	0.677 ± 0.009	0.055	1
115	NGVS-J123223.49+115755.0	188.0978941	11.9652688	0.032	20.191 ± 0.001	1.161 ± 0.005	0.667 ± 0.002	0.861 ± 0.003	1.014 ± 0.003	0.954 ± 0.004	0.005	1
116	NGVS-J123225.37+121956.8	188.1056843	12.3324523	0.027	20.516 ± 0.002	1.028 ± 0.006	0.513 ± 0.003	0.749 ± 0.004	0.841 ± 0.005	0.660 ± 0.006	0.081	1
117	NGVS-J123244.39+113638.1	188.1849358	11.6105850	0.043	21.657 ± 0.003	0.919 ± 0.011	0.510 ± 0.005	0.740 ± 0.007	0.819 ± 0.011	1.126 ± 0.011	0.016	0
118	NGVS-J123244.97+120411.6	188.1873822	12.0699039	0.035	21.538 ± 0.003	1.014 ± 0.011	0.495 ± 0.005	0.754 ± 0.006	0.867 ± 0.010	0.727 ± 0.011	0.057	1
119	NGVS-J123253.34+120711.5	188.2222540	12.1198664	0.036	21.274 ± 0.003	0.893 ± 0.009	0.466 ± 0.005	0.692 ± 0.006	0.754 ± 0.010	0.992 ± 0.008	−0.004	0
120	NGVS-J123256.67+115104.7	188.2361303	11.8512962	0.034	20.193 ± 0.001	0.964 ± 0.004	0.501 ± 0.002	0.736 ± 0.002	0.820 ± 0.003	0.570 ± 0.004	0.015	1
121	NGVS-J123313.42+130553.0	188.3059241	13.0980602	0.030	20.929 ± 0.002	0.879 ± 0.007	0.426 ± 0.003	0.704 ± 0.004	0.828 ± 0.006	1.126 ± 0.007	0.026	0
122	NGVS-J123319.67+121112.3	188.3319655	12.1867587	0.034	20.027 ± 0.001	0.977 ± 0.005	0.481 ± 0.002	0.673 ± 0.003	0.785 ± 0.004	0.994 ± 0.004	0.134	0
123	NGVS-J123329.47+121017.4	188.3727924	12.1715180	0.034	20.567 ± 0.001	1.013 ± 0.005	0.522 ± 0.003	0.764 ± 0.003	0.888 ± 0.004	0.656 ± 0.006	0.076	1
124	NGVS-J123346.31+115702.3	188.4429573	11.9506379	0.036	20.996 ± 0.003	1.315 ± 0.009	0.608 ± 0.004	0.961 ± 0.005	1.141 ± 0.006	1.250 ± 0.006	−0.002	1
125	NGVS-J123348.68+124647.9	188.4528619	12.7799771	0.031	20.327 ± 0.001	1.081 ± 0.006	0.586 ± 0.002	0.837 ± 0.003	0.996 ± 0.004	0.915 ± 0.006	0.343	0
126	NGVS-J123351.52+122346.0	188.4646471	12.3961311	0.032	19.679 ± 0.001	1.176 ± 0.003	0.653 ± 0.002	0.953 ± 0.002	1.100 ± 0.002	1.842 ± 0.002	0.211	0
127	NGVS-J123359.60+114730.9	188.4983267	11.7919191	0.040	21.375 ± 0.003	1.005 ± 0.009	0.459 ± 0.005	0.777 ± 0.006	0.888 ± 0.009	0.505 ± 0.015	0.011	1

Notes. (1) Object ID number; (2) Object name in NGVS; (3) R.A.; (4) decl.; (5) Galactic extinction (Schlegel et al. 1998); (6) Aperture-corrected g magnitude within a 3-arcsec diameter aperture. Only SExtractor errors are accounted for here; (7–11) Colors measured in a 1.5-arcsec diameter aperture; (12) Envelope parameter defined in Equation (8); (13) Object flag, 0—not UCD, 1—confirmed or possible UCD.

Download table as:  ASCIITypeset images: 1 2 3 4 5 6

Table 3.  Structural Properties and Redshift Information for UCD Candidates in the M87 Region

ID	NGVSID	gk	ik	rh, g	rh, i	rh(ACS)	rh(S11)	vr(S11)	vr(MMT)	vr(AAT)	vr(SDSS)	Class	uiKs	ugz	UCD	OtherName
		(mag)	(mag)	(pc)	(pc)	(pc)	(pc)	(km s−1)	(km s−1)	(km s−1)	(km s−1)
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)	(12)	(13)	(14)	(15)	(16)	(17)
1	NGVS-J122623.21+121925.2	19.468 ± 0.022	18.742 ± 0.022	36.59 ± 1.27	35.42 ± 1.08	...	...	...	...	46450	...	1	0	1	0	⋯
2	NGVS-J122628.69+125642.6	19.792 ± 0.011	18.852 ± 0.013	17.38 ± 0.72	15.99 ± 0.72	...	...	...	...	−186	...	1	1	1	1	⋯
3	NGVS-J122633.05+123847.6	21.391 ± 0.014	20.651 ± 0.007	11.26 ± 0.57	10.99 ± 0.49	...	...	...	5322	...	...	1	1	1	0	⋯
4	NGVS-J122636.42+125512.9	18.972 ± 0.006	18.021 ± 0.006	18.01 ± 0.33	17.34 ± 0.27	...	...	...	...	−93	...	1	1	1	1	⋯
5	NGVS-J122638.52+123702.7	20.616 ± 0.007	19.843 ± 0.008	17.86 ± 0.40	18.04 ± 0.43	...	...	...	...	...	...	1	1	1	1	⋯
6	NGVS-J122638.79+124545.8	20.564 ± 0.007	19.823 ± 0.010	15.93 ± 0.30	15.03 ± 0.42	...	...	...	...	...	...	1	1	1	1	⋯
7	NGVS-J122643.32+121743.9	20.830 ± 0.004	20.112 ± 0.007	11.88 ± 0.39	10.28 ± 0.45	...	...	...	...	...	...	2	1	1	0	⋯
8	NGVS-J122646.48+131732.2	21.446 ± 0.004	20.683 ± 0.013	12.97 ± 0.25	14.53 ± 0.49	...	...	...	...	...	...	1	0	1	0	⋯
9	NGVS-J122647.07+122714.0	19.559 ± 0.013	18.692 ± 0.019	24.11 ± 0.99	18.68 ± 1.23	...	...	...	...	...	1411	2	1	0	0	VCC940
10	NGVS-J122649.87+115931.8	21.498 ± 0.010	20.633 ± 0.014	19.94 ± 0.54	25.22 ± 0.55	...	...	...	...	...	...	1	0	1	0	⋯
11	NGVS-J122656.56+123532.2	19.881 ± 0.006	19.041 ± 0.006	17.32 ± 0.37	15.98 ± 0.58	...	...	...	...	...	...	1	1	1	1	⋯
12	NGVS-J122708.43+132009.0	21.330 ± 0.011	20.617 ± 0.016	19.94 ± 0.79	19.24 ± 0.96	...	...	...	...	...	150598	2	1	1	0	VCC972a
13	NGVS-J122726.54+131150.7	20.901 ± 0.010	20.098 ± 0.012	22.47 ± 0.52	26.28 ± 0.63	...	...	...	...	...	...	1	0	1	0	⋯
14	NGVS-J122727.19+125546.0	21.046 ± 0.011	20.344 ± 0.006	12.54 ± 0.42	11.43 ± 0.25	...	...	...	...	...	...	1	1	1	1	⋯
15	NGVS-J122729.00+131903.4	21.386 ± 0.020	20.579 ± 0.026	18.07 ± 1.02	15.90 ± 1.11	...	...	...	...	...	...	3	0	1	0	⋯
16	NGVS-J122745.56+124356.4	21.577 ± 0.015	20.834 ± 0.008	13.51 ± 0.75	12.77 ± 0.51	...	...	...	198108	...	...	1	1	1	0	⋯
17	NGVS-J122804.51+121507.6	21.416 ± 0.009	20.577 ± 0.016	21.62 ± 0.52	25.06 ± 0.72	...	...	...	...	...	...	1	0	1	0	⋯
18	NGVS-J122806.62+122436.4	21.004 ± 0.011	20.260 ± 0.009	12.03 ± 0.57	12.82 ± 0.33	...	...	...	156806	...	...	1	1	1	0	M87UCD29
19	NGVS-J122837.21+122845.6	21.081 ± 0.005	20.333 ± 0.006	12.61 ± 0.31	12.51 ± 0.42	...	...	...	...	...	...	1	1	1	1	M87UCD30
20	NGVS-J122856.90+130220.5	21.408 ± 0.009	20.700 ± 0.009	14.41 ± 0.55	15.05 ± 0.40	...	...	...	...	...	...	1	1	1	1	⋯
21	NGVS-J122910.66+124304.1	20.947 ± 0.004	20.157 ± 0.005	12.69 ± 0.25	11.29 ± 0.34	...	...	...	...	...	...	1	1	1	1	M87UCD24
22	NGVS-J122914.82+113622.4	21.226 ± 0.007	20.458 ± 0.009	20.58 ± 0.45	22.36 ± 0.42	...	...	...	...	...	...	1	0	1	0	⋯
23	NGVS-J122914.87+115343.8	20.263 ± 0.008	19.489 ± 0.007	12.43 ± 0.40	10.79 ± 0.37	...	...	...	...	...	...	1	1	1	1	M87UCD34
24	NGVS-J122925.49+121835.8	20.880 ± 0.006	20.111 ± 0.014	22.21 ± 0.37	24.86 ± 0.70	...	...	...	...	...	...	1	0	1	0	⋯
25	NGVS-J122936.29+113708.5	21.112 ± 0.010	20.268 ± 0.021	14.96 ± 0.48	16.84 ± 0.78	...	...	...	...	...	...	1	0	1	0	⋯
26	NGVS-J122937.04+130620.9	20.998 ± 0.010	20.289 ± 0.012	19.97 ± 0.57	23.95 ± 0.61	...	...	...	...	...	...	1	0	1	0	⋯
27	NGVS-J122937.93+114058.1	21.263 ± 0.005	20.545 ± 0.008	12.33 ± 0.28	11.17 ± 0.37	...	...	...	...	...	...	1	1	1	1	⋯
28	NGVS-J122940.39+122728.1	19.967 ± 0.004	19.173 ± 0.005	20.30 ± 0.22	21.51 ± 0.21	...	...	...	...	1400	...	1	1	1	1	M87UCD5
29	NGVS-J122941.32+123952.4	20.328 ± 0.008	19.537 ± 0.009	17.50 ± 0.43	15.60 ± 0.45	...	...	...	...	1754	...	1	1	1	1	M87UCD20
30	NGVS-J122941.56+124427.6	21.000 ± 0.006	20.167 ± 0.006	10.98 ± 0.40	11.17 ± 0.30	...	...	...	1261	...	...	1	1	1	1	M87UCD23
31	NGVS-J122942.29+131727.6	19.780 ± 0.008	18.717 ± 0.011	19.64 ± 0.55	20.28 ± 1.06	...	...	...	53553	...	...	3	1	1	0	⋯
32	NGVS-J122945.26+125100.9	20.560 ± 0.004	19.819 ± 0.004	12.34 ± 0.18	11.35 ± 0.27	...	...	...	1156	1070	...	1	1	1	1	M87UCD8
33	NGVS-J122947.20+121717.8	19.655 ± 0.011	18.776 ± 0.014	32.01 ± 0.75	40.93 ± 1.17	...	...	...	37236	...	...	1	0	1	0	⋯
34	NGVS-J122950.93+123653.2	21.517 ± 0.009	20.802 ± 0.010	9.30 ± 0.37	12.09 ± 0.31	...	...	...	184673	...	...	1	1	1	0	⋯
35	NGVS-J122952.28+123737.8	20.881 ± 0.005	19.994 ± 0.006	10.58 ± 0.21	13.13 ± 0.28	...	...	...	886	...	...	1	1	1	1	M87UCD22
36	NGVS-J122952.41+123504.1	19.697 ± 0.007	18.934 ± 0.007	31.20 ± 0.39	37.14 ± 0.54	...	...	...	...	...	...	1	1	1	1	⋯
37	NGVS-J122954.98+123350.9	20.602 ± 0.008	19.891 ± 0.013	23.81 ± 0.46	24.71 ± 0.72	...	...	...	...	...	...	1	1	1	1	⋯
38	NGVS-J122956.35+131312.1	20.091 ± 0.004	19.392 ± 0.005	15.86 ± 0.24	11.82 ± 0.27	...	...	...	43	824	...	2	1	1	0	VCC1244
39	NGVS-J122957.12+123602.9	20.312 ± 0.006	19.591 ± 0.007	12.51 ± 0.21	13.31 ± 0.27	...	...	1489	1506	...	...	1	1	1	1	H65115
40	NGVS-J123001.95+124226.9	19.862 ± 0.005	19.191 ± 0.011	22.18 ± 0.30	20.96 ± 0.51	...	...	...	...	1115	...	1	1	1	1	M87UCD10
41	NGVS-J123002.46+123633.8	20.250 ± 0.003	19.461 ± 0.003	14.84 ± 0.18	15.08 ± 0.15	...	...	...	...	1514	...	1	1	1	1	M87UCD6
42	NGVS-J123004.05+120714.0	19.802 ± 0.005	19.021 ± 0.005	11.52 ± 0.19	10.47 ± 0.24	...	...	1168	1166	...	...	1	1	1	1	H18539
43	NGVS-J123006.06+123954.0	19.514 ± 0.003	18.690 ± 0.003	16.80 ± 0.10	18.98 ± 0.19	...	...	...	...	1160	...	1	1	1	1	M87UCD7
44	NGVS-J123006.13+122435.3	20.635 ± 0.004	19.797 ± 0.008	12.95 ± 0.21	12.31 ± 0.52	...	...	...	1878	...	...	1	1	1	1	M87UCD28
45	NGVS-J123007.57+123631.0	19.120 ± 0.002	18.285 ± 0.006	12.37 ± 0.13	12.09 ± 0.31	...	12.1	1223	1235	1241	...	1	1	1	1	VUCD1
46	NGVS-J123009.82+123736.5	21.097 ± 0.004	20.312 ± 0.005	11.19 ± 0.16	11.44 ± 0.24	...	...	...	1261	...	...	1	1	1	1	M87UCD37
47	NGVS-J123010.00+123604.7	21.566 ± 0.008	20.826 ± 0.010	12.88 ± 0.45	11.65 ± 0.57	...	...	...	...	...	...	1	1	1	1	⋯
48	NGVS-J123010.89+121143.7	21.099 ± 0.009	20.432 ± 0.016	19.64 ± 0.63	16.28 ± 1.21	...	...	...	...	...	−420	2	1	1	0	VCC1264
49	NGVS-J123011.07+124721.7	20.640 ± 0.015	19.880 ± 0.006	11.71 ± 0.91	10.92 ± 0.40	...	...	...	...	...	...	1	1	1	1	⋯
50	NGVS-J123014.74+120726.5	21.294 ± 0.007	20.617 ± 0.013	12.92 ± 0.31	13.87 ± 0.54	...	...	...	...	...	...	1	0	1	0	⋯
51	NGVS-J123016.54+121556.8	20.074 ± 0.006	19.340 ± 0.021	17.28 ± 0.36	17.11 ± 1.08	...	...	...	2021	...	...	1	1	1	1	M87UCD26
52	NGVS-J123017.80+114447.4	19.064 ± 0.022	18.112 ± 0.021	30.65 ± 1.33	28.02 ± 1.45	...	...	...	26492	...	...	3	0	1	0	⋯
53	NGVS-J123019.63+120924.6	21.119 ± 0.007	20.432 ± 0.010	11.38 ± 0.25	9.96 ± 0.37	...	...	831	881	...	...	1	1	1	1	H20718
54	NGVS-J123020.05+115518.7	19.330 ± 0.003	18.532 ± 0.004	23.31 ± 0.19	22.30 ± 0.21	...	...	...	1276	1397	...	1	1	1	1	M87UCD3
55	NGVS-J123021.83+122402.4	20.004 ± 0.010	19.042 ± 0.018	11.70 ± 0.46	11.65 ± 0.96	...	...	...	...	1271	...	1	1	1	1	M87UCD4
56	NGVS-J123022.97+123148.7	19.793 ± 0.004	19.069 ± 0.004	18.85 ± 0.22	17.29 ± 0.16	...	...	...	532	546	...	1	1	1	1	M87UCD9
57	NGVS-J123025.75+122621.1	20.501 ± 0.004	19.754 ± 0.015	13.70 ± 0.28	12.61 ± 0.48	...	...	1368	...	...	...	1	1	1	1	S1631
58	NGVS-J123026.56+122044.6	20.348 ± 0.005	19.592 ± 0.016	18.03 ± 0.28	18.15 ± 0.64	...	26.4	1135	...	1124	...	1	1	1	1	S1629
59	NGVS-J123026.89+122331.1	19.908 ± 0.004	19.093 ± 0.009	16.45 ± 0.25	17.17 ± 0.42	...	...	1404	...	1409	...	1	1	1	1	S1617
60	NGVS-J123029.91+123822.2	20.452 ± 0.024	19.806 ± 0.021	19.04 ± 0.91	18.91 ± 0.75	...	...	...	...	845	...	1	1	1	1	M87UCD11
61	NGVS-J123030.86+121841.7	19.794 ± 0.012	19.017 ± 0.011	15.95 ± 0.55	14.76 ± 0.52	...	...	2425	...	2365	...	1	1	1	1	VUCD10
62	NGVS-J123031.44+125156.6	20.234 ± 0.023	19.317 ± 0.010	12.19 ± 0.81	12.58 ± 0.61	...	...	...	...	1511	...	1	1	1	1	M87UCD12
63	NGVS-J123031.53+122602.6	20.302 ± 0.007	19.577 ± 0.016	14.66 ± 0.31	14.63 ± 0.58	...	...	858	...	857	...	1	1	1	1	S1504
64	NGVS-J123033.43+122954.3	19.164 ± 0.011	18.412 ± 0.011	33.66 ± 0.69	32.21 ± 0.60	36.50 ± 1.71	28.9	1296	1261	1301	...	1	1	1	1	H55930
65	NGVS-J123034.12+122246.5	21.328 ± 0.015	20.575 ± 0.009	16.68 ± 0.54	17.38 ± 0.39	...	...	1100	...	...	...	1	1	1	1	S1449
66	NGVS-J123035.02+123452.7	20.423 ± 0.010	19.701 ± 0.008	33.24 ± 0.49	33.72 ± 0.52	...	...	...	...	...	...	1	1	1	1	⋯
67	NGVS-J123036.52+122152.8	20.536 ± 0.009	19.783 ± 0.016	16.69 ± 0.33	15.87 ± 0.61	...	...	...	...	...	...	1	1	1	1	⋯
68	NGVS-J123039.16+122132.5	20.786 ± 0.007	19.995 ± 0.013	13.70 ± 0.45	13.37 ± 0.64	...	...	1086	...	...	...	1	1	1	1	S1301
69	NGVS-J123041.81+122341.2	21.163 ± 0.010	20.446 ± 0.016	15.00 ± 0.52	13.76 ± 0.61	...	29.9	1211	...	...	...	1	1	1	1	S1201
70	NGVS-J123043.25+122212.4	21.191 ± 0.006	20.385 ± 0.011	16.92 ± 0.31	17.65 ± 0.55	...	...	...	...	...	...	1	1	1	1	⋯
71	NGVS-J123045.34+122033.5	20.612 ± 0.007	19.848 ± 0.020	24.22 ± 0.51	23.67 ± 0.90	...	...	2023	...	...	...	1	1	1	1	S1044
72	NGVS-J123045.95+113752.5	21.177 ± 0.013	20.340 ± 0.016	24.05 ± 0.70	31.37 ± 1.00	...	...	...	...	...	...	1	0	1	0	⋯
73	NGVS-J123046.50+122017.7	20.824 ± 0.011	20.047 ± 0.010	15.44 ± 0.42	15.60 ± 0.31	...	...	1004	...	...	...	1	1	1	1	S991
74	NGVS-J123047.40+123301.7	19.513 ± 0.007	18.644 ± 0.004	18.09 ± 0.33	17.02 ± 0.22	...	...	1379	1322	1343	...	1	1	1	1	F6
75	NGVS-J123047.66+120825.2	19.687 ± 0.021	19.007 ± 0.012	23.68 ± 1.20	23.56 ± 0.48	...	...	...	...	1265	...	1	1	1	1	M87UCD2
76	NGVS-J123047.70+122430.5	19.727 ± 0.010	18.963 ± 0.011	26.12 ± 0.54	26.15 ± 0.57	23.45 ± 0.43	36.3	1283	...	1331	...	1	1	1	1	S928
77	NGVS-J123048.19+123510.7	19.212 ± 0.004	18.416 ± 0.005	11.41 ± 0.18	10.52 ± 0.22	...	14.1	824	...	921	...	1	1	1	1	VUCD2
78	NGVS-J123049.28+123718.2	19.984 ± 0.007	19.196 ± 0.012	12.89 ± 0.24	12.25 ± 0.52	...	...	...	1620	1601	...	1	1	1	1	M87UCD13
79	NGVS-J123049.49+121426.9	20.593 ± 0.010	19.840 ± 0.030	16.69 ± 0.36	17.55 ± 1.12	...	...	...	...	...	...	1	1	1	1	⋯
80	NGVS-J123051.07+122611.9	19.722 ± 0.004	18.808 ± 0.007	13.52 ± 0.33	13.46 ± 0.46	...	...	1131	...	1142	...	1	1	1	1	S804
81	NGVS-J123051.65+121409.9	21.078 ± 0.006	20.396 ± 0.007	13.03 ± 0.19	14.29 ± 0.30	...	13.7	1299	...	...	...	1	1	1	1	H27916
82	NGVS-J123051.75+122053.3	20.824 ± 0.004	20.061 ± 0.007	11.80 ± 0.09	11.61 ± 0.21	...	15.3	1163	...	...	...	1	1	1	1	S796
83	NGVS-J123053.88+121712.4	21.052 ± 0.008	20.178 ± 0.013	20.48 ± 0.43	21.35 ± 0.70	19.38 ± 0.28	24.8	1020	...	...	...	1	1	1	1	S731
84	NGVS-J123054.66+122022.6	21.273 ± 0.008	20.555 ± 0.010	20.00 ± 0.33	20.85 ± 0.60	...	23.7	1333	...	...	...	1	1	1	1	S682
85	NGVS-J123101.47+121924.5	19.659 ± 0.009	18.695 ± 0.014	14.88 ± 0.31	15.20 ± 0.36	...	14.7	1860	...	1856	...	1	1	1	1	S417
86	NGVS-J123102.14+122749.7	20.592 ± 0.009	19.859 ± 0.015	23.47 ± 0.43	23.31 ± 0.51	...	...	1215	...	...	...	1	1	1	1	S376
87	NGVS-J123102.59+123414.1	19.794 ± 0.005	19.093 ± 0.018	18.19 ± 0.21	17.47 ± 0.99	...	...	1192	...	1187	...	1	1	1	1	F12
88	NGVS-J123103.69+123213.0	20.063 ± 0.006	19.359 ± 0.011	13.16 ± 0.24	11.73 ± 0.60	...	...	681	717	708	...	1	1	1	1	H59533
89	NGVS-J123104.35+131042.5	20.297 ± 0.009	19.405 ± 0.012	11.61 ± 0.36	10.16 ± 0.48	...	...	...	1321	1344	...	1	1	1	1	M87UCD14
90	NGVS-J123104.43+122321.2	20.537 ± 0.013	19.790 ± 0.014	32.75 ± 0.76	34.73 ± 0.88	...	...	1157	...	...	...	1	1	1	1	S323
91	NGVS-J123104.80+131436.6	20.743 ± 0.007	20.012 ± 0.013	13.51 ± 0.43	15.29 ± 0.57	...	...	...	...	...	...	1	1	1	1	⋯
92	NGVS-J123110.14+121627.9	21.183 ± 0.013	20.382 ± 0.015	20.91 ± 0.60	19.49 ± 0.60	...	...	1818	...	...	...	1	1	1	1	S6003
93	NGVS-J123110.42+130550.4	20.864 ± 0.008	20.154 ± 0.011	10.95 ± 0.55	11.88 ± 0.55	...	...	...	1607	...	1529	2	1	1	0	VCC1340
94	NGVS-J123111.31+123001.0	20.870 ± 0.010	20.013 ± 0.010	11.91 ± 0.48	12.33 ± 0.55	...	...	...	...	...	...	1	1	1	1	M87UCD36
95	NGVS-J123116.32+121845.4	20.864 ± 0.013	20.049 ± 0.011	25.92 ± 0.57	26.64 ± 0.69	...	...	1848	1787	...	...	1	1	1	1	S41
96	NGVS-J123120.00+121158.1	20.518 ± 0.006	19.750 ± 0.009	11.26 ± 0.33	11.50 ± 0.22	...	...	1282	1250	1346	...	1	1	1	1	H24581
97	NGVS-J123124.75+122525.8	19.833 ± 0.003	19.077 ± 0.007	13.45 ± 0.19	12.75 ± 0.22	...	...	...	1785	1781	...	1	1	1	1	M87UCD18
98	NGVS-J123125.25+121931.8	20.096 ± 0.015	19.344 ± 0.008	32.83 ± 1.09	33.30 ± 0.54	...	...	...	...	...	...	1	1	1	1	M87UCD32
99	NGVS-J123128.36+122503.6	19.388 ± 0.020	18.594 ± 0.009	14.02 ± 0.85	12.85 ± 0.37	...	18.8	2100	2116	2111	...	1	1	1	1	VUCD6
100	NGVS-J123131.70+113610.7	21.173 ± 0.019	20.397 ± 0.019	13.40 ± 1.14	13.09 ± 0.96	...	...	...	...	...	1838	2	1	1	0	VCC1366
101	NGVS-J123131.70+124130.4	19.378 ± 0.004	18.552 ± 0.008	38.73 ± 0.28	36.45 ± 0.43	...	...	...	1090	1138	...	1	1	0	1	M87UCD16
102	NGVS-J123135.13+123459.4	20.195 ± 0.012	19.305 ± 0.010	11.02 ± 0.54	12.27 ± 0.42	...	...	...	...	948	...	1	1	1	1	M87UCD17
103	NGVS-J123137.44+121740.7	20.655 ± 0.009	19.941 ± 0.012	11.67 ± 0.36	11.10 ± 0.40	...	...	...	−50	...	...	1	1	1	1	M87UCD21
104	NGVS-J123138.53+115923.9	20.743 ± 0.014	19.964 ± 0.010	19.15 ± 0.52	19.81 ± 0.61	...	...	...	...	...	...	1	1	1	1	M87UCD25
105	NGVS-J123145.95+122721.1	21.399 ± 0.008	20.711 ± 0.010	12.33 ± 0.39	11.89 ± 0.37	...	...	1320	...	...	...	1	1	1	1	H51655
106	NGVS-J123151.34+123925.2	20.047 ± 0.012	19.198 ± 0.011	13.96 ± 0.72	16.08 ± 0.78	...	...	...	...	...	1279	2	1	1	0	VCC1386
107	NGVS-J123152.96+115052.9	20.784 ± 0.020	19.853 ± 0.018	26.64 ± 0.79	31.65 ± 0.96	...	...	...	...	...	...	4	0	1	0	⋯
108	NGVS-J123157.60+124929.6	20.293 ± 0.009	19.584 ± 0.005	19.10 ± 0.31	18.77 ± 0.21	...	...	...	1094	1082	...	1	1	1	1	M87UCD19
109	NGVS-J123157.99+131534.1	19.506 ± 0.010	18.766 ± 0.010	38.68 ± 0.55	41.84 ± 0.61	...	...	...	...	1271	...	1	1	1	1	M87UCD15
110	NGVS-J123204.35+122030.3	19.722 ± 0.008	18.917 ± 0.008	12.61 ± 0.30	12.00 ± 0.46	...	...	1641	1649	1649	...	1	1	1	1	VUCD8
111	NGVS-J123211.80+113818.6	19.676 ± 0.007	18.884 ± 0.020	35.45 ± 0.36	39.12 ± 1.00	...	...	...	...	51399	...	1	0	1	0	⋯
112	NGVS-J123214.45+120159.0	20.702 ± 0.008	19.864 ± 0.013	16.74 ± 0.60	15.71 ± 0.67	...	...	...	1825	...	...	1	1	1	1	M87UCD33
113	NGVS-J123214.58+120305.3	19.504 ± 0.007	18.643 ± 0.010	17.65 ± 0.51	17.19 ± 0.66	...	25.4	1216	1276	1292	...	1	1	1	1	VUCD9
114	NGVS-J123221.10+121613.4	20.675 ± 0.006	19.911 ± 0.010	29.86 ± 0.37	28.87 ± 0.49	...	...	...	...	...	...	1	1	1	1	⋯
115	NGVS-J123223.49+115755.0	20.241 ± 0.007	19.391 ± 0.007	11.58 ± 0.48	11.50 ± 0.33	...	...	...	1005	...	...	1	1	1	1	M87UCD35
116	NGVS-J123225.37+121956.8	20.586 ± 0.007	19.860 ± 0.010	12.03 ± 0.40	10.95 ± 0.58	...	...	...	...	...	...	1	1	1	1	M87UCD27
117	NGVS-J123244.39+113638.1	21.599 ± 0.015	20.870 ± 0.018	22.00 ± 0.54	21.78 ± 0.76	...	...	...	...	...	...	1	0	1	0	⋯
118	NGVS-J123244.97+120411.6	21.615 ± 0.011	20.894 ± 0.018	11.98 ± 0.51	10.38 ± 0.88	...	...	...	...	...	...	1	1	1	1	⋯
119	NGVS-J123253.34+120711.5	21.250 ± 0.025	20.520 ± 0.034	17.73 ± 0.84	21.38 ± 0.99	...	...	...	...	...	...	3	0	1	0	⋯
120	NGVS-J123256.67+115104.7	20.190 ± 0.020	19.456 ± 0.017	16.44 ± 0.69	17.26 ± 0.52	...	...	...	...	...	...	1	1	1	1	⋯
121	NGVS-J123313.42+130553.0	20.976 ± 0.007	20.262 ± 0.005	11.35 ± 0.36	15.59 ± 0.36	...	...	...	25326	...	...	1	0	1	0	⋯
122	NGVS-J123319.67+121112.3	19.829 ± 0.028	19.012 ± 0.010	41.88 ± 1.48	52.30 ± 0.88	...	...	...	...	...	...	3	0	1	0	⋯
123	NGVS-J123329.47+121017.4	20.637 ± 0.006	19.899 ± 0.012	12.46 ± 0.36	11.47 ± 0.52	...	...	1317	...	...	...	1	1	1	1	F16
124	NGVS-J123346.31+115702.3	21.043 ± 0.009	20.097 ± 0.011	11.53 ± 0.37	10.98 ± 0.25	...	...	...	1351	...	...	1	1	1	1	M87UCD39
125	NGVS-J123348.68+124647.9	20.424 ± 0.012	19.604 ± 0.013	15.03 ± 0.75	16.83 ± 0.84	...	...	...	...	...	1134	2	1	1	0	VCC1523
126	NGVS-J123351.52+122346.0	19.768 ± 0.010	18.718 ± 0.014	17.98 ± 0.79	23.90 ± 0.93	...	...	...	65704	...	...	3	0	1	0	⋯
127	NGVS-J123359.60+114730.9	21.408 ± 0.006	20.646 ± 0.015	12.76 ± 0.27	12.24 ± 0.37	...	...	...	...	...	...	1	1	1	1

Notes. (1) Object ID number; (2) Object name in NGVS; (3–4) King model magnitudes in g and i bands; (5–6) Half-light radii in g and i bands; (7) Half-light radius measured using HST imaging (Haşegan et al. 2005); (8) Half-light radius from Strader et al. (2011); (9–12) Radial velocity from Strader et al. (2011), MMT/Hectospec and 2dF/AAOmega AAT program (Zhang et al. 2015), and SDSS (York et al. 2000); (13) Class parameter: 1—probable UCD, 2—dwarf nucleus, 3—background galaxy, 4—other type of contaminant; (14) Flag for whether the object was selected in the u*iK_s color–color diagram: 0—no, 1—yes; (15) Flag for whether the object selected in the u*gz color–color diagram: 0—no, 1—yes; (16) Object flag, 0—not UCD, 1—confirmed or possible UCD; (17) Alternative names, if available.

^aThe SDSS redshift measurement has ${\mathtt{ZWARNING}}=68,$ which means that the spectrum has SMALL_DELTA_CHI2 and NEGATIVE_EMISSION (Bolton et al. 2012). Although the SDSS velocity indicates this VCC-cataloged galaxy is a background galaxy, its diffuse envelope and prominent nucleus strongly suggest that it is a bonafide cluster member.

Download table as:  ASCIITypeset images: 1 2 3 4 5 6

2.4.4. Constraints on Membership and Contamination from Spectroscopy

The NGVS includes four background (BG) fields located far from the cluster center. Each field is offset from M87 by ∼16°, or roughly three virial radii.³¹ Because these four fields were observed in the same filters as the other survey fields (u*griz), and under typical NGVS observing conditions with identical exposure times and dithering strategies, we can use these fields to estimate the level of contamination in our UCD samples selected from u*gz imaging.

In all, the background fields contain a total of 10,322 objects between our UCD magnitude selection limits of 18.5 ≤ g ≤ 21.5. Of these, 1145 objects are additionally located in the region of the u*gz diagram occupied by UCDs and GCs. The selection on surface brightness described in Section 2.4.2 is quite effective at removing galaxies, however, and leaves a total of only 174 sources. Among these 174 sources, 19 were found to satisfy the three size conditions described in Section 2.3. After a visual inspection, only 9 "UCDs" were left in the sample, a slightly higher number than the four spurious sources identified based on spectroscopy (Section 2.4.4) of u*iK_s-selected sources. While the field-to-field variance may be significant (there were 2, 1, 4, and 2 contaminants found in BG1, BG2, BG3 and BG4 fields, respectively), the number density of contaminants in the u*gz-selected sample is ${\rm{\Sigma }}{(\mathrm{UCD})}_{{u}^{*}{gz}}$ = 2.2 ± 0.7 deg⁻².

Unfortunately, there is no K_s-band imaging for these four background fields. To estimate the contamination in our u*iK_s-selected sample, we use the CFHTLS-D2 field as a proxy background field for the NGVS. CFHTLS-D2 field is one of the four CFHTLS Deep Survey pointings observed in u*griz filters. In this region, there is also a deep K_s imaging from UltraVISTA (McCracken et al. 2012) which is an ultra-deep, near-infrared survey using VISTA telescope. We find 2731 objects in this field in the magnitude range 18.5 ≤ g ≤ 21.5 mag; reassuringly, this is quite similar to the mean number of 2580 objects per NGVS background field in this range. A total of 36 CFHTLS objects fall within the UCD/GC region of the u*iK_s diagram, only one of which remains after selecting on size and surface brightness. Thus, the u*iK_s-selected UCD sample is found to be exceptionally clean, with a contaminant surface density of ${\rm{\Sigma }}{(\mathrm{UCD})}_{{u}^{*}{{iK}}_{s}}\simeq 0.9\pm 0.9$ deg⁻².

The complete sample of 127 UCD candidates in the M87 region is presented in Tables 2 and 3. Recall that this sample was selected entirely on the basis of magnitude, color (specifically, location in the u*iK_s and/or u*gz diagrams), half-light radius and surface brightness, as described in the preceding sections. For completeness, we list all candidates that were selected before visual inspection and including even those objects which are known from spectroscopy to be background galaxies. A total of 16 of these 127 UCD candidates were subsequently rejected following a careful examination of the NGVS images (i.e., the objects with class parameters of 2, 3, or 4 in Table 3).

Information on the M87 UCD candidates is divided into two tables. Table 2 gives, from left to right, each object's identification number, NGVS identifier, right ascension, declination, extinction (Schlegel et al. 1998), g-band magnitude measured in an aperture with a diameter of 16 pixels and corrected to the SDSS PSF magnitude system, and a variety of 8-pixel diameter aperture colors. Note that these are the observed magnitudes, prior to any correction for extinction. The final two columns of Table 2 give the parameter Δ_env, defined in Section 4, followed by our final UCD classification: "1" if the candidate is a probable UCD after considering all possible diagnostics (magnitude, color, size, morphology and/or spectroscopy) and "0" otherwise. A total of 92 objects have UCD classifications of 1.

Table 3 records the object identification number, NGVS identifier, g- and i-band KINGPHOT magnitudes, and radii, followed by previous r_h measurements from the ACSVCS (Haşegan et al. 2005; Jordán et al. 2005) or from Strader et al. (2011). The next four columns give the measured radial velocity, if available, from Strader et al. (2011), MMT or AAT (Zhang et al. 2015), and SDSS. The NGVS class parameter is given in the next column, followed by two flags to indicate whether the object falls inside (1) or outside (0) the GC/UCD selection regions in the u*iK_s and u*gz diagrams, respectively, and the UCD classification parameter defined above. The final column gives alternative names from the literature (Binggeli et al. 1985; Hanes et al. 2001; Jones et al. 2006; Firth et al. 2008; Harris 2009a; Zhang et al. 2015). One other object (ID = 7 = NGVS-J122643.32+121743.9) was identified as a faint, nucleated galaxy in our search for low-mass galaxies in the Virgo cluster core.

In the M87 region, 106 of the 127 candidates listed in Tables 2 and 3 were selected based on magnitude, location in u*iK_s diagram, size, and surface brightness (uiK_s = 1 in Table 3). Among the 106 u*iK_s-selected candidates, 96 were classified as class = 1 objects. Radial velocities reveal four of these objects to be background galaxies (see Section 2.4.4), bringing our cleaned sample of UCDs in the M87 region to 92. Our cleaned sample of 92 UCD candidates is much larger than any previous studied UCD samples in this region (e.g., 34 UCDs in Brodie et al. 2011 and Strader et al. 2011). In addition, the homogeneity is another advantage of our sample. In addition, we also have a homogeneous sample GC and dE,N (see Sections 2.7 and 2.8), which allows us to compare the properties between UCDs, GCs and dwarf nuclei.

As described in Section 2.4.2, we also select UCD candidates based on the u*gz diagram in the M87, M49 and M60 regions. Based on magnitude, location in u*gz diagram, size and surface brightness, we find 125, 50 and 29 UCD candidates, and 110, 40, and 23 are classified as class = 1 in these three regions. 8 and 12 candidates in the M87 and M49 regions have velocity v_r > 3500 km s⁻¹, which we deem to be compact, background galaxies. For the M60 region, only two candidates have velocity measurements and both of them are Virgo members (v_r < 3500 km s⁻¹). Finally, the cleaned u*gz-selected samples have 102, 28 and 23 confirmed or candidate UCDs in these three regions. Tables 4 and 5 show the photometric and structure properties of M49 UCD candidates, while Tables 6 and 7 show the properties of M60 UCD candidates.

Table 4.  Photometric Properties of UCD Candidates in the M49 Region

ID	NGVSID	αJ2000	δJ2000	$E(B-V)$	g16	${({u}^{*}-g)}_{8}$	${(g-i)}_{8}$	${(g-z)}_{8}$	Δenv	UCD
		(degree)	(degree)	(mag)	(mag)	(mag)	(mag)	(mag)	(mag)
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)
1	NGVS-J122708.94+074228.3	186.7872607	7.7078639	0.024	19.429 ± 0.001	1.025 ± 0.003	0.813 ± 0.002	0.955 ± 0.002	0.239	1
2	NGVS-J122718.40+081154.2	186.8266527	8.1983810	0.023	20.966 ± 0.002	1.076 ± 0.008	0.794 ± 0.004	0.900 ± 0.007	−0.140	0
3	NGVS-J122735.11+072518.7	186.8962982	7.4218483	0.022	20.992 ± 0.003	0.923 ± 0.008	0.678 ± 0.005	0.790 ± 0.008	0.085	0
4	NGVS-J122741.97+075613.3	186.9248642	7.9370367	0.025	21.193 ± 0.003	1.146 ± 0.012	0.747 ± 0.006	0.862 ± 0.010	0.075	0
5	NGVS-J122744.26+072542.5	186.9344272	7.4284640	0.022	20.645 ± 0.002	0.968 ± 0.006	0.683 ± 0.004	0.778 ± 0.006	0.103	1
6	NGVS-J122803.46+065343.1	187.0144136	6.8953085	0.020	21.446 ± 0.004	0.987 ± 0.011	0.737 ± 0.007	0.868 ± 0.011	0.140	1
7	NGVS-J122806.14+065909.0	187.0255686	6.9858243	0.020	20.272 ± 0.002	1.485 ± 0.008	0.984 ± 0.004	1.250 ± 0.005	0.321	1
8	NGVS-J122806.31+080342.8	187.0262901	8.0618891	0.022	21.475 ± 0.003	0.923 ± 0.013	0.697 ± 0.007	0.795 ± 0.013	0.092	0
9	NGVS-J122818.37+074924.9	187.0765475	7.8235740	0.024	21.563 ± 0.003	1.011 ± 0.013	0.787 ± 0.007	0.935 ± 0.012	0.148	0
10	NGVS-J122828.41+083115.5	187.1183613	8.5209855	0.018	20.961 ± 0.002	0.984 ± 0.007	0.707 ± 0.005	0.832 ± 0.007	0.124	0
11	NGVS-J122828.60+070228.2	187.1191854	7.0411563	0.018	20.713 ± 0.002	0.907 ± 0.007	0.799 ± 0.005	0.892 ± 0.007	0.221	1
12	NGVS-J122830.49+071929.1	187.1270287	7.3247459	0.021	20.459 ± 0.002	1.113 ± 0.006	0.795 ± 0.004	0.947 ± 0.006	0.425	0
13	NGVS-J122849.25+075919.4	187.2051905	7.9887156	0.022	21.260 ± 0.003	0.918 ± 0.010	0.844 ± 0.006	0.914 ± 0.010	0.077	1
14	NGVS-J122850.66+082621.0	187.2110768	8.4391793	0.021	21.534 ± 0.004	0.930 ± 0.013	0.759 ± 0.007	0.864 ± 0.013	0.069	0
15	NGVS-J122857.99+083513.8	187.2416238	8.5871653	0.021	18.812 ± 0.001	1.479 ± 0.003	1.072 ± 0.001	1.325 ± 0.001	0.184	0
16	NGVS-J122858.00+071759.9	187.2416690	7.2999606	0.022	20.185 ± 0.001	1.119 ± 0.005	0.892 ± 0.003	1.056 ± 0.004	0.154	0
17	NGVS-J122906.90+073558.8	187.2787298	7.5996681	0.023	21.230 ± 0.003	0.986 ± 0.009	0.759 ± 0.006	0.827 ± 0.010	0.129	0
18	NGVS-J122917.85+082558.1	187.3243594	8.4328050	0.022	18.640 ± 0.001	1.320 ± 0.003	0.993 ± 0.001	1.217 ± 0.002	0.185	0
19	NGVS-J122922.85+074901.2	187.3452098	7.8169941	0.025	20.813 ± 0.002	1.022 ± 0.007	0.762 ± 0.004	0.843 ± 0.006	0.088	1
20	NGVS-J122924.89+072105.3	187.3536954	7.3514762	0.020	21.317 ± 0.003	0.917 ± 0.010	0.670 ± 0.008	0.721 ± 0.012	0.244	0
21	NGVS-J122925.10+075407.0	187.3545827	7.9019461	0.024	20.231 ± 0.001	1.030 ± 0.005	0.762 ± 0.003	0.842 ± 0.004	0.051	1
22	NGVS-J122926.23+081658.8	187.3593098	8.2829991	0.022	21.453 ± 0.003	1.076 ± 0.012	0.746 ± 0.007	0.892 ± 0.012	0.036	1
23	NGVS-J122928.21+075355.4	187.3675253	7.8987154	0.024	19.860 ± 0.001	1.266 ± 0.005	0.918 ± 0.002	1.030 ± 0.003	0.093	1
24	NGVS-J122928.62+075824.6	187.3692499	7.9734990	0.023	20.932 ± 0.004	1.123 ± 0.012	0.720 ± 0.006	0.819 ± 0.011	0.033	1
25	NGVS-J122934.41+080540.9	187.3933684	8.0947073	0.022	20.493 ± 0.002	0.977 ± 0.006	0.725 ± 0.004	0.804 ± 0.006	0.092	0
26	NGVS-J122948.37+080042.0	187.4515565	8.0116645	0.022	20.741 ± 0.004	1.084 ± 0.010	0.808 ± 0.006	0.930 ± 0.009	0.105	1
27	NGVS-J122957.08+074820.0	187.4878332	7.8055582	0.024	19.737 ± 0.001	1.035 ± 0.004	0.851 ± 0.002	0.985 ± 0.003	0.063	1
28	NGVS-J122958.06+080409.2	187.4919199	8.0692203	0.022	19.754 ± 0.001	1.197 ± 0.004	0.896 ± 0.002	1.041 ± 0.003	0.016	1
29	NGVS-J123002.49+075846.7	187.5103664	7.9796416	0.022	20.983 ± 0.003	1.004 ± 0.010	0.738 ± 0.006	0.833 ± 0.010	0.064	1
30	NGVS-J123004.35+073932.2	187.5181421	7.6589449	0.020	21.511 ± 0.004	0.967 ± 0.010	0.716 ± 0.008	0.799 ± 0.011	0.079	1
31	NGVS-J123006.03+074901.2	187.5251438	7.8169882	0.023	21.255 ± 0.003	1.003 ± 0.009	0.738 ± 0.006	0.879 ± 0.009	0.056	1
32	NGVS-J123006.89+080509.5	187.5287169	8.0859729	0.022	20.455 ± 0.002	0.999 ± 0.005	0.769 ± 0.003	0.856 ± 0.005	0.069	1
33	NGVS-J123008.39+082507.4	187.5349653	8.4187179	0.021	19.044 ± 0.001	1.210 ± 0.002	0.873 ± 0.001	1.044 ± 0.002	0.212	1
34	NGVS-J123008.69+065353.4	187.5362036	6.8981683	0.017	20.164 ± 0.001	0.982 ± 0.004	0.818 ± 0.003	0.947 ± 0.004	0.109	0
35	NGVS-J123009.17+074127.5	187.5381980	7.6909633	0.021	19.526 ± 0.001	1.316 ± 0.003	0.864 ± 0.002	1.067 ± 0.002	0.086	1
36	NGVS-J123015.56+083445.0	187.5648407	8.5791729	0.020	20.896 ± 0.002	1.258 ± 0.007	0.887 ± 0.004	1.043 ± 0.006	0.049	1
37	NGVS-J123016.65+080454.4	187.5693858	8.0817884	0.022	20.859 ± 0.002	1.035 ± 0.007	0.801 ± 0.004	0.891 ± 0.006	0.074	1
38	NGVS-J123018.06+075024.9	187.5752391	7.8402478	0.021	19.466 ± 0.001	1.175 ± 0.003	0.862 ± 0.002	1.045 ± 0.002	0.210	1
39	NGVS-J123029.94+074755.5	187.6247355	7.7987386	0.021	20.397 ± 0.002	1.185 ± 0.005	0.831 ± 0.003	0.996 ± 0.004	0.053	1
40	NGVS-J123047.31+073619.4	187.6971300	7.6053799	0.019	20.161 ± 0.001	0.982 ± 0.005	0.752 ± 0.003	0.878 ± 0.004	0.282	0
41	NGVS-J123048.49+065420.2	187.7020501	6.9056234	0.017	21.457 ± 0.003	1.144 ± 0.011	0.774 ± 0.006	0.905 ± 0.010	0.094	0
42	NGVS-J123109.91+080405.3	187.7912805	8.0681353	0.024	19.812 ± 0.001	0.977 ± 0.003	0.744 ± 0.002	0.865 ± 0.003	0.124	1
43	NGVS-J123113.76+074811.9	187.8073500	7.8033039	0.020	21.293 ± 0.003	0.993 ± 0.009	0.745 ± 0.006	0.843 ± 0.009	0.056	1
44	NGVS-J123148.91+071620.9	187.9537817	7.2724780	0.019	19.244 ± 0.001	1.237 ± 0.003	0.803 ± 0.002	1.032 ± 0.002	0.205	0
45	NGVS-J123152.37+064659.4	187.9681966	6.7831568	0.021	20.163 ± 0.001	0.972 ± 0.005	0.778 ± 0.003	0.900 ± 0.004	0.157	0
46	NGVS-J123212.59+074047.6	188.0524452	7.6798850	0.021	21.226 ± 0.003	0.944 ± 0.009	0.716 ± 0.006	0.839 ± 0.009	0.098	0
47	NGVS-J123320.46+080226.6	188.3352586	8.0407230	0.019	20.996 ± 0.002	1.011 ± 0.008	0.819 ± 0.005	0.890 ± 0.007	0.059	0
48	NGVS-J123327.85+070649.5	188.3660383	7.1137599	0.023	20.978 ± 0.002	1.143 ± 0.008	0.752 ± 0.005	0.896 ± 0.008	0.168	0
49	NGVS-J123359.09+074244.6	188.4962125	7.7124026	0.022	20.319 ± 0.002	1.124 ± 0.005	0.829 ± 0.003	0.969 ± 0.004	0.021	1
50	NGVS-J123402.20+064950.3	188.5091560	6.8306518	0.022	21.218 ± 0.003	0.939 ± 0.009	0.651 ± 0.006	0.709 ± 0.010	0.084	1

Notes. (1) Object ID number; (2) Object name in NGVS; (3) R.A.; (4) decl.; (5) Galactic extinction (Schlegel et al. 1998); (6) Aperture-corrected g magnitude within a 3-arcsec diameter aperture. Only SExtractor errors are accounted for here; (7–9) Colors measured in a 1.5-arcsec diameter aperture; (10) Envelope parameter defined in (8); (11) Object flag, 0—not UCD, 1—confirmed or possible UCD.

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Table 6.  Photometric Properties of UCD Candidates in the M60 Region

ID	NGVSID	αJ2000	δJ2000	$E(B-V)$	g16	${({u}^{*}-g)}_{8}$	${(g-i)}_{8}$	${(g-z)}_{8}$	Δenv	UCD
		(degree)	(degree)	(mag)	(mag)	(mag)	(mag)	(mag)	(mag)
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)
1	NGVS-J123909.32+112147.9	189.7888329	11.3633175	0.033	21.159 ± 0.003	1.415 ± 0.010	1.004 ± 0.005	1.175 ± 0.007	0.057	1
2	NGVS-J123948.33+105157.0	189.9513674	10.8658447	0.022	20.858 ± 0.002	1.244 ± 0.009	0.907 ± 0.004	1.043 ± 0.006	0.130	0
3	NGVS-J123949.21+110135.3	189.9550398	11.0264758	0.024	21.167 ± 0.003	1.338 ± 0.011	0.981 ± 0.005	1.173 ± 0.007	0.078	1
4	NGVS-J123950.99+112805.1	189.9624727	11.4680886	0.039	20.763 ± 0.002	1.208 ± 0.007	0.934 ± 0.004	1.162 ± 0.005	0.114	0
5	NGVS-J124002.08+105517.2	190.0086686	10.9214418	0.022	21.420 ± 0.003	0.994 ± 0.012	0.664 ± 0.007	0.735 ± 0.012	0.261	1
6	NGVS-J124049.54+121138.1	190.2064072	12.1939068	0.039	21.348 ± 0.003	1.219 ± 0.011	0.981 ± 0.005	1.127 ± 0.008	0.083	1
7	NGVS-J124115.49+103811.9	190.3145415	10.6366475	0.024	21.350 ± 0.003	1.119 ± 0.011	0.865 ± 0.006	1.037 ± 0.009	0.069	1
8	NGVS-J124151.11+105311.7	190.4629499	10.8865742	0.021	19.805 ± 0.001	1.405 ± 0.005	1.014 ± 0.002	1.242 ± 0.003	0.306	0
9	NGVS-J124205.30+103959.1	190.5220991	10.6664070	0.026	21.462 ± 0.003	0.977 ± 0.010	0.729 ± 0.007	0.828 ± 0.010	0.070	1
10	NGVS-J124206.89+115144.7	190.5287016	11.8624190	0.028	20.966 ± 0.002	1.113 ± 0.007	0.828 ± 0.004	0.963 ± 0.006	0.061	1
11	NGVS-J124209.61+113654.7	190.5400246	11.6151888	0.030	20.940 ± 0.002	1.051 ± 0.007	0.782 ± 0.004	0.881 ± 0.006	0.059	1
12	NGVS-J124216.65+114428.6	190.5693756	11.7412681	0.031	21.387 ± 0.007	1.468 ± 0.023	0.998 ± 0.012	1.258 ± 0.012	0.043	1
13	NGVS-J124229.83+112029.7	190.6242758	11.3415871	0.027	19.975 ± 0.001	1.169 ± 0.004	0.830 ± 0.002	0.977 ± 0.003	0.045	1
14	NGVS-J124232.60+115702.6	190.6358256	11.9507163	0.028	21.166 ± 0.003	1.012 ± 0.008	0.780 ± 0.005	0.896 ± 0.008	0.040	1
15	NGVS-J124235.74+114254.2	190.6489118	11.7150453	0.030	21.423 ± 0.003	1.169 ± 0.011	0.888 ± 0.006	1.080 ± 0.008	0.055	1
16	NGVS-J124238.75+115646.8	190.6614439	11.9463314	0.028	21.602 ± 0.004	0.910 ± 0.011	0.715 ± 0.008	0.786 ± 0.012	0.056	0
17	NGVS-J124244.72+111240.5	190.6863239	11.2112384	0.027	20.593 ± 0.002	1.246 ± 0.007	0.832 ± 0.004	1.007 ± 0.005	0.115	1
18	NGVS-J124248.01+115513.8	190.7000359	11.9204879	0.027	19.812 ± 0.001	1.025 ± 0.003	0.818 ± 0.002	0.930 ± 0.003	0.120	1
19	NGVS-J124312.47+111230.2	190.8019424	11.2083931	0.030	21.313 ± 0.003	1.148 ± 0.011	0.749 ± 0.006	0.888 ± 0.009	0.061	1
20	NGVS-J124315.49+113922.8	190.8145574	11.6563462	0.027	20.719 ± 0.002	1.014 ± 0.005	0.666 ± 0.004	0.792 ± 0.005	0.037	1
21	NGVS-J124324.30+112343.2	190.8512567	11.3953461	0.024	20.782 ± 0.002	0.987 ± 0.006	0.732 ± 0.004	0.814 ± 0.006	0.083	1
22	NGVS-J124352.42+112534.2	190.9684091	11.4261669	0.024	18.830 ± 0.001	1.412 ± 0.002	0.968 ± 0.001	1.165 ± 0.001	0.080	1
23	NGVS-J124352.48+112518.3	190.9686634	11.4217508	0.025	20.312 ± 0.001	1.072 ± 0.005	0.773 ± 0.003	0.875 ± 0.004	0.048	1
24	NGVS-J124437.85+103801.1	191.1577272	10.6336481	0.026	20.012 ± 0.001	1.110 ± 0.004	0.858 ± 0.002	0.989 ± 0.003	0.085	1
25	NGVS-J124524.02+110535.2	191.3500929	11.0930994	0.031	19.454 ± 0.001	1.397 ± 0.003	1.034 ± 0.002	1.158 ± 0.002	0.055	1
26	NGVS-J124531.21+112357.2	191.3800543	11.3992236	0.027	20.351 ± 0.001	1.083 ± 0.005	0.806 ± 0.003	0.898 ± 0.004	0.112	1
27	NGVS-J124532.99+114125.3	191.3874620	11.6903730	0.026	21.275 ± 0.003	1.011 ± 0.009	0.809 ± 0.006	0.978 ± 0.008	0.138	0
28	NGVS-J124538.98+114526.8	191.4124258	11.7574345	0.028	21.282 ± 0.004	1.034 ± 0.013	0.702 ± 0.009	0.786 ± 0.013	0.118	0
29	NGVS-J124539.33+104808.1	191.4138693	10.8022486	0.024	19.993 ± 0.001	1.239 ± 0.005	0.899 ± 0.003	1.041 ± 0.003	0.099	1

Note. (1) Object ID number; (2) Object name in NGVS; (3) R.A.; (4) decl.; (5) Galactic extinction (Schlegel et al. 1998); (6) Aperture-corrected g magnitude within a 3-arcsec diameter aperture. Only SExtractor errors are accounted for here; (7–9) Colors measured in a 1.5-arcsec diameter aperture; (10) Envelope parameter defined in 8; (11) Object flag, 0—not UCD, 1—confirmed or possible UCD.

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