The nuclear near-infrared spectral properties of nearby galaxies

Abstract

Near-infrared observations can provide a wealth of information addressing numerous outstanding questions about the physics and lifecycles of galaxies. Many diagnostic lines are present in this wavelength range: H2 and coronal lines can be used to trace molecular gas and super-excited, often outflowing, material; obscured broad line regions (BLRs) can be revealed; [FeII] emission may probe shock-excited gas associated with supernova activity or jets; and stellar absorption lines may measure stages of stellar evolution that have less obvious optical signatures, to name just a few examples. NIR observations of inactive galaxies, starbursts, and active galactic nuclei (AGN) have already given rise to advances in areas from stellar population studies (Rieke et al. 1980, McLeod et al. 1993, Origlia et al. 1993, Riffel et al. 2009, Zibetti et al. 2013, Martins et al. 2013) to black hole (BH) mass measurements (Landt et al. 2013, Riffel et al. 2013). The Palomar XD is a collaboration of astronomers from around the world. As a part of the Palomar XD collaboration, we obtained Gemini NIR spectroscopy of the nuclei of 50 galaxies, almost all from the Palomar survey (Ho et al. 1995, 1997a). The Palomar galaxy survey provides a spectral atlas of a near-complete, flux-limited (B < 12.5 mag) sample of nearby, northern galaxies. Our aim is to expand our understanding of AGN and their hosts using the many NIR diagnostic possibilities. At this point of this project the data paper has being accepted for publication (Mason et al. 2015, ApJ), and part of the analysis of the data has being initiated: a comparison of velocity dispersions derived from the calcium triplet and CO band heads (Riffel et al. 2014, MNRAS) and modeling of the stellar absorption features in the highest-quality spectra (Riffel et al., submitted to MNRAS). The following projects are being developed: 1) Analysis of the emission-line spectra (González-Martín et al., Martins et al.). 2) Presentation of the extended emission-line spectrum of NGC 4388 (Rodríguez-Ardila et al.). 3) Full stellar population synthesis of the whole data set (Riffel et al.). 4) The dust and accretion disk emission in the low-luminosity AGN (Biddle, Mason et al.). During this meeting we intend to actively work on the first three items above. (AU)