NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-03-21 T08:58:51 PDT
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For refcode 2015MNRAS.446.2823R:
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Copyright by Royal Astronomical Society. 2015MNRAS.446.2823R Differences between CO- and calcium triplet-derived velocity dispersions in spiral galaxies: evidence for central star formation? Riffel, Rogemar A.; Ho, Luis C.; Mason, Rachel; Rodriguez-Ardila, Alberto; Martins, Lucimara; Riffel, Rogerio; Diaz, Ruben; Colina, Luis; Alonso-Herrero, Almudena; Flohic, Helene; Gonzalez Martin, Omaira; Lira, Paulina; McDermid, Richard; Ramos Almeida, Cristina; Schiavon, Ricardo; Thanjavur, Karun; Ruschel-Dutra, Daniel; Winge, Claudia; Perlman, Eric Abstract. We examine the stellar velocity dispersions (sigma) of a sample of 48 galaxies, 35 of which are spirals, from the Palomar nearby galaxy survey. It is known that for ultra-luminous infrared galaxies (ULIRGs) and merger remnants, the sigma derived from the near-infrared CO band heads is smaller than that measured from optical lines, while no discrepancy between these measurements is found for early-type galaxies. No such studies are available for spiral galaxies - the subject of this paper. We used cross-dispersed spectroscopic data obtained with the Gemini Near-Infrared Spectrograph, with spectral coverage from 0.85 to 2.5 micron, to obtain sigma measurements from the 2.29 micron CO band heads (sigma_CO_) and the 0.85 micron calcium triplet (sigma_CaT_). For the spiral galaxies in the sample, we found that sigma_CO_ is smaller than sigma_CaT_, with a mean fractional difference of 14.3 per cent. The best fit to the data is given by sigma_opt_ = (46.0 +/- 18.1) + (0.85 +/- 0.12)sigma_CO_. This 'sigma-discrepancy' may be related to the presence of warm dust, as suggested by a slight correlation between the discrepancy and the infrared luminosity. This is consistent with studies that have found no sigma-discrepancy in dust-poor early-type galaxies, and a much larger discrepancy in dusty merger remnants and ULIRGs. That sigma_CO_ is lower than sigma_opt_ may also indicate the presence of a dynamically cold stellar population component. This would agree with the spatial correspondence between low-sigma_CO_ and young/intermediate-age stellar populations that has been observed in spatially resolved spectroscopy of a handful of galaxies. Key words: galaxies: active, galaxies: kinematics and dynamics, galaxies: star formation, infrared: galaxies
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