César Esteban et al. 2009 ApJ 700 654 doi:10.1088/0004-637X/700/1/654
César Esteban1,2, Fabio Bresolin3, Manuel Peimbert4, Jorge García-Rojas4, Antonio Peimbert4 and Adal Mesa-Delgado1
Show affiliationsWe present very deep spectrophotometry of 14 bright extragalactic H II regions belonging to spiral, irregular, and blue compact galaxies. The data for 13 objects were taken with the High Resolution Echelle Spectrometer on the Keck I telescope. We have measured C II recombination lines in 10 of the objects and O II recombination lines in eight of them. We have determined electron temperatures from line ratios of several ions, especially those of low ionization potential. We have found a rather tight linear empirical relation between T e([N II]) and T e([O III]). We have found that O II lines give always larger abundances than [O III] lines. Moreover, the difference of both O++ abundance determinations—the so-called abundance discrepancy factor—is very similar in all the objects, with a mean value of 0.26 ± 0.09 dex, independent of the properties of the H II region and of the parent galaxy. Using the observed recombination lines, we have determined the O, C, and C/O radial abundance gradients for three spiral galaxies: M33, M101, and NGC 2403, finding that C abundance gradients are always steeper than those of O, producing negative C/O gradients across the galactic disks. This result is similar to that found in the Milky Way and has important implications for chemical evolution models and the nucleosynthesis of C.
galaxies: abundances; galaxies: individual (M31, M33, M83, M101, NGC 1741, NGC 2366, NGC 2403, NGC 4395, NGC 4861); galaxies: ISM; galaxies: spiral; H II regions
Issue 1 (2009 July 20)
Received 2009 February 27, accepted for publication 2009 May 21
Published 2009 July 6
César Esteban et al. 2009 ApJ 700 654
T P Flanagan 1957 J. Sci. Instrum. 34 450
S K Bhattacharya and S -I Chu 1985 J. Phys. B: At. Mol. Phys. 18 L275
Edson D Leonel and P V E McClintock 2006 J. Phys. A: Math. Gen. 39 11399
Pei-Qing Jin et al 2006 J. Phys. A: Math. Gen. 39 7115
O E Barndorff-Nielsen and R D Gill 2000 J. Phys. A: Math. Gen. 33 4481
V. M. Kaspi et al. 2001 ApJ 560 371
E A Schiff 2004 J. Phys.: Condens. Matter 16 S5265
Jacqueline Kessler-Silacci et al. 2006 ApJ 639 275
M. Audard et al 2005 ApJ 635 L81