An optical monitoring survey in nearby dwarf galaxies was carried out with the 2.5 m Isaac Newton Telescope. Fifty-five dwarf galaxies and four isolated globular clusters in the Local Group were observed with the Wide Field Camera. The main aims of this survey are to identify the most evolved asymptotic giant branch (AGB) stars and red supergiants at the end-point of their evolution based on their pulsational instability, use their distribution over luminosity to reconstruct the star formation history, quantify the dust production and mass loss from modeling the multiwavelength spectral energy distributions (SEDs), and relate this to luminosity and radius variations. In this first of a series of papers, we present the methodology of the variability survey and describe the photometric catalog of the Andromeda I (And I) dwarf galaxy as an example of the survey, and we discuss the identified long period variable (LPV) stars. We detected 5581 stars and identified 59 LPV candidates within two half-light radii of the center of And I. The amplitudes of these candidates range from 0.2 to 3 mag in the i-band. Seventy-five percent of detected sources and 98% of LPV candidates are detected at mid-infrared wavelengths. We show evidence for the presence of dust-producing AGB stars in this galaxy including five extreme AGB (x-AGB) stars, and we model some of their SEDs. A distance modulus of 24.41 mag for And I was determined based on the tip of the red giant branch. Also, a half-light radius of 3.′2 ± 0.′3 was calculated.

We develop a kinematical model for the Milky Way Si iv-bearing gas to determine its density distribution and kinematics. This model is constrained by a column density line-shape sample extracted from the Hubble Space Telescope/Cosmic Origins Spectrograph archival data, which contains 186 active galactic nucleus sight lines. We find that the Si iv ion density distribution is dominated by an extended disk along the z-direction (above or below the midplane), i.e., , where z ₀ is the scale height of kpc (northern hemisphere) and kpc (southern hemisphere). The density distribution of the disk in the radial direction shows a sharp edge at 15–20 kpc given by, , where r ₀ ≈ 12.5 ± 0.6 kpc. The difference of density distributions over r _XY and z directions indicates that the warm gas traced by Si iv is mainly associated with disk processes (e.g., feedback or cycling gas) rather than accretion. We estimate the mass of the warm gas (within 50 kpc) is (assuming Z ≈ 0.5 Z _⊙), and a 3 σ upper limit of (excluding the Magellanic system). Kinematically, the warm gas disk is nearly co-rotating with the stellar disk at , which lags the midplane rotation by about (within 5 kpc). Meanwhile, we note that the warm gas in the northern hemisphere has significant accretion with v _acc of 69 ± 7 at 10 kpc (an accretion rate of ), while in the southern hemisphere, there is no measurable accretion, with an upper limit of 0.4 M _⊙ yr ⁻¹.

The presence of elongations in active-region (AR) polarities, called magnetic tongues, is mostly visible during their emergence phase. AR tilts have been measured thoroughly using long-term white-light (WL) databases, sometimes combined with magnetic-field information. Since the influence of magnetic tongues on WL tilt measurements has not been taken into account before, we aim to investigate their role in tilt-angle values and to compare them with those derived from LOS magnetograms. We apply four methods to compute the tilt angle of generally bipolar ARs: one applies the k-means algorithm to WL data, a second one includes the magnetic-field sign of the polarities to WL data, and a third one uses the magnetic flux-weighted center of each polarity. The tilt values computed in any of these ways are affected by the presence of magnetic tongues. Therefore, we apply the newly developed Core Field Fit Estimator (CoFFE) method to separate the magnetic flux in the tongues from that in the AR core. We compare the four computed tilt-angle values, as well as these with the ones reported in long-term WL databases. For ARs with low-magnetic-flux tongues, the different methods report consistent tilt-angle values. But for ARs with high-flux tongues, there are noticeable discrepancies between all methods, indicating that magnetic tongues differently affect WL and magnetic data. However, in general, CoFFE achieves a better estimation of the main bipole tilt because it removes both the effect of tongues as well as the emergence of secondary bipoles when it occurs in between the main bipole magnetic polarities.

Binary black holes (BBHs) are thought to form in different environments, including the galactic field and (globular, nuclear, young, and open) star clusters. Here, we propose a method to estimate the fingerprints of the main BBH formation channels associated with these different environments. We show that the metallicity distribution of galaxies in the local universe along with the relative amount of mergers forming in the field or in star clusters determine the main properties of the BBH population. Our fiducial model predicts that the heaviest merger to date, GW170729, originated from a progenitor that underwent 2–3 merger events in a dense star cluster, possibly a galactic nucleus. The model predicts that at least one merger remnant out of a hundred BBH mergers in the local universe has mass , and one in a thousand can reach a mass as large as . Such massive black holes would bridge the gap between stellar-mass and intermediate-mass black holes. The relative number of low- and high-mass BBHs can help us unravel the fingerprints of different formation channels. Based on the assumptions of our model, we expect that isolated binaries are the main channel of BBH merger formation if of the whole BBH population has remnants with masses , whereas % of remnants having masses points to a significant subpopulation of dynamically formed BBH binaries.

Physico-chemical modifications induced by swift heavy ions on methane-water (CH ₄:H ₂O) ices at 15 K are analyzed. Ice films, at concentrations of (1:3) and (1:15), were irradiated by 40 MeV ⁵⁸Ni ¹¹⁺ ions. Fourier transform transmission spectroscopy in the mid-range was used to monitor the evolution ices at 15 K as a function of projectile fluence. New IR bands appearing for the irradiated (CH ₄:H ₂O) (1:3) ice are attributed to the synthesized molecules: C ₃H ₈, HCO, H ₂CO, CO, CO ₂, H ₂O ₂, HCOOH, CH ₃OH, C ₂H ₅OH, and CH ₃CHO. For the irradiated (CH ₄:H ₂O) (1:15) ice, the abundances of the compounds containing two carbons atoms are lower than those for the (1:3) ice; in contrast, CH ₃OH and H ₂O ₂ abundances increase when compared to the values obtained with the (1:3) ice. After irradiation, the ices were warmed up until 110 K, when the IR spectra reveal features of complex organic molecules. The destruction and formation cross sections and the sputtering yields of the ice mixtures are estimated. These findings provide possible pathways for the occurrence of compounds rich in C, O, and H, which are indeed observed in the cold regions of the universe such as ices in grain mantles of the interstellar medium and circumstellar envelopes.