Stellar populations of classical and pseudo-bulges for a sample of isolated spiral galaxies

In this paper we present the stellar population synthesis results for a sample of 75 bulges in isolated spiral Sb-Sc galaxies, using the spectroscopic data from the Sloan Digital Sky Survey and the STARLIGHT code. We find that both pseudo-bulges and classical bulges in our sample are predominantly composed of old stellar populations, with mean mass-weighted stellar age around 10 Gyr. While the stellar population of pseudo-bulges is, in general, younger than that of classical bulges, the difference is not significant, which indicates that it is hard to distinguish pseudo-bulges from classical bulges, at least for these isolated galaxies, only based on their stellar populations. Pseudo-bulges have star formation activities with relatively longer timescale than classical bulges, indicating that secular evolution is more important in this kind of systems. Our results also show that pseudo-bulges have a lower stellar velocity dispersion than their classical counterparts, which suggests that classical bulges are more dispersion-supported than pseudo-bulges.Comment: 10 pages, 8 figures. Accepted for publication in Astrophysics & Space Scienc

An atlas of calcium triplet spectra of active galaxies

We present a spectroscopic atlas of active galactic nuclei covering the region around the λλ8498, 8542, 8662 calcium triplet (CaT). The sample comprises 78 objects, divided into 43 Seyfert 2s, 26 Seyfert Is, three starburst and six normal galaxies. The spectra pertain to the inner ∼300 pc in radius, and thus sample the central kinematics and stellar populations of active galaxies. The data are used to measure stellar velocity dispersions (σ*) with both cross-correlation and direct fitting methods. These measurements are found to be in good agreement with each other and with those in previous studies for objects in common. The CaT equivalent width is also measured. We find average values and sample dispersions of WCaT of 4.6 ± 2.0,7.0 ± 1.0 and 7.7 ± 1.0 Å for Seyfert Is, Seyfert 2s and normal galaxies, respectively. We further present an atlas of [S m]λ9069 emission-line profiles for a subset of 40 galaxies. These data are analysed in a companion paper which addresses the connection between stellar and narrow-line region kinematics, the behaviour of the CaT equivalent width as a function of σ*, activity type and stellar population properties.AGR, LRV, NVA, RCF and TSB acknowledge the support from CAPES, CNPq and Instituto do Milenio. RGD acknowledges support by Spanish Ministry of Science and Technology (MCYT) through grant AYA-2004-02703

Cosmic evolution of the spatially resolved star formation rate and stellar mass of the CALIFA survey

We investigate the cosmic evolution of the absolute and specific star formation rate (SFR, sSFR) of galaxies as derived from a spatially resolved study of the stellar populations in a set of 366 nearby galaxies from the Calar Alto Legacy Integral Field Area (CALIFA) survey. The sample spans stellar masses from M ∼ 10 to 10M and a wide range of Hubble types. The analysis combines images obtained with the Galaxy Evolution Explorer (GALEX; far-ultraviolet and near-ultraviolet) and Sloan Digital Sky Survey (SDSS; u; g; r; i; z) with the 4000 Å break, Hβ, and [MgFe]′ indices measured from the CALIFA data cubes to constrain parametric models for the star formation history (SFH), which are then used to study the cosmic evolution of the SFR density (ρSFR), the sSFR, the main sequence of star formation (MSSF), and the stellar mass density (ρ). Several SFH laws are used to fit the observational constrains. A delayed-τ model, SFR ∝ (t - t) exp(-(t - t)=τ), provides the best results, in good agreement with those obtained from cosmological surveys. Our main results from this model are that (a) the mass currently in the inner (≤0:5 half-light radius, HLR) regions formed at earlier epochs than the mass in the outer (1-2 HLR) regions of galaxies. The time since the onset of the star formation is longer in the inner regions (t ∼ 13-10 Gyr) than in the outer ones (t ∼ 11-9 Gyr) for all the morphologies, while the e-folding timescale τ in the inner region is similar to or shorter than in the outer regions. These results confirm that galaxies of any Hubble type grow inside-out. (b) The sSFR declines rapidly as the Universe evolves, and faster for early- than for late-type galaxies, and for the inner than for the outer regions of galaxies. (c) The evolution of ρSFR and ρ agrees well with results from cosmological surveys, particularly with the recent results from the Galaxy And Mass Assembly (GAMA), the G10-Cosmological Evolution Survey (COSMOS), and the 3D Hubble Space Telescope (HST) survey. At low redshift, z ≤ 0:5, most star formation takes place in the outer regions of late spiral galaxies, while at z > 2; the inner regions of the progenitors of the current E and S0 are the main contributors to ρSFR. (d) Similarly, the inner regions of galaxies are the main contributor to ρ at z > 0:5, growing their mass faster than the outer regions, with a lookback time at 50% ρ of t ∼ 9 and 6 Gyr for the inner and outer regions. (e) The MSSF follows a power law at high redshift, with the slope evolving with time but always remaining sub-linear, in good agreement with the Illustris simulation. (f) In agreement with galaxy surveys at different redshifts, the average SFH of CALIFA galaxies indicates that galaxies grow their mass mainly in a mode that is well represented by a delayed-τ model, with the peak at z ∼ 2 and an e-folding time of ∼3:9 Gyr.© 2018 ESO.Support from the Spanish Ministerio de Economía y Competitividad, through projects AYA2016-77846-P, AYA2014-57490-P, AYA2010-15081, and the Junta de Andalucía FQ1580 is gratefully acknowledged.Peer Reviewe