We present the stellar kinematic maps of a large sample of galaxies from the integral-field spectroscopic survey CALIFA. The sample comprises 300 galaxies displaying a wide range of morphologies ...across the Hubble sequence, from ellipticals to late-type spirals. This dataset allows us to homogeneously extract stellar kinematics up to several effective radii. In this paper, we describe the level of completeness of this subset of galaxies withrespect to the full CALIFA sample, as well as the virtues and limitations of the kinematic extraction compared to other well-known integral-field surveys. In addition, we provide averaged integrated velocity dispersion radial profiles for different galaxy types, which are particularly useful to apply aperture corrections for single aperture measurements or poorly resolved stellar kinematics of high-redshift sources. The work presented in this paper sets the basis for the study of more general properties of galaxies that will be explored in subsequent papers of the survey.
The Javalambre Photometric Local Universe Survey (J-PLUS ) is an ongoing 12-band photometric optical survey, observing thousands of square degrees of the Northern Hemisphere from the dedicated ...JAST/T80 telescope at the Observatorio Astrofísico de Javalambre (OAJ). The T80Cam is a camera with a field of view of 2 deg2 mounted on a telescope with a diameter of 83 cm, and is equipped with a unique system of filters spanning the entire optical range (3500–10 000 Å). This filter system is a combination of broad-, medium-, and narrow-band filters, optimally designed to extract the rest-frame spectral features (the 3700–4000 Å Balmer break region, Hδ, Ca H+K, the G band, and the Mg b and Ca triplets) that are key to characterizing stellar types and delivering a low-resolution photospectrum for each pixel of the observed sky. With a typical depth of AB ∼21.25 mag per band, this filter set thus allows for an unbiased and accurate characterization of the stellar population in our Galaxy, it provides an unprecedented 2D photospectral information for all resolved galaxies in the local Universe, as well as accurate photo-z estimates (at the δ z/(1 + z)∼0.005–0.03 precision level) for moderately bright (up to r ∼ 20 mag) extragalactic sources. While some narrow-band filters are designed for the study of particular emission features (O II/λ3727, Hα/λ6563) up to z < 0.017, they also provide well-defined windows for the analysis of other emission lines at higher redshifts. As a result, J-PLUS has the potential to contribute to a wide range of fields in Astrophysics, both in the nearby Universe (Milky Way structure, globular clusters, 2D IFU-like studies, stellar populations of nearby and moderate-redshift galaxies, clusters of galaxies) and at high redshifts (emission-line galaxies at z ≈ 0.77, 2.2, and 4.4, quasi-stellar objects, etc.). With this paper, we release the first ∼1000 deg2 of J-PLUS data, containing about 4.3 million stars and 3.0 million galaxies at r < 21 mag. With a goal of 8500 deg2 for the total J-PLUS footprint, these numbers are expected to rise to about 35 million stars and 24 million galaxies by the end of the survey.
Star formation along the Hubble sequence Delgado, R M Gonzalez; Fernandes, R Cid; Perez, E ...
Astronomy and astrophysics (Berlin),
6/2016, Letnik:
590
Journal Article
Recenzirano
Odprti dostop
The spatially resolved stellar population content of today's galaxies holds important information for understanding the different processes that contribute to the star formation and mass assembly ...histories of galaxies. The aim of this paper is to characterize the radial structure of the star formation rate (SFR) in galaxies in the nearby Universe as represented by a uniquely rich and diverse data set drawn from the CALIFA survey. The sample under study contains 416 galaxies observed with integral field spectroscopy, covering a wide range of Hubble types and stellar masses ranging from M sub(?)~ 10 super(9) to 7 x 10 super(11)M sub(?). Spectral synthesis techniques are applied to the datacubes to derive 2D maps and radial profiles of the intensity of the star formation rate in the recent past (Sigma sub(SFR)), as well as related properties, such as the local specific star formation rate (sSFR), defined as the ratio between Sigma sub(SFR) and the stellar mass surface density (mu sub(*)). To emphasize the behavior of these properties for galaxies that are on and off the main sequence of star formation (MSSF), we stack the individual radial profiles in seven bins of galaxy morphology (E, S0, Sa, Sb, Sbc, Sc, and Sd), and several stellar masses. Our main results are: (a) the intensity of the star formation rate shows declining profiles that exhibit very small differences between spirals with values at R= 1 half light radius (HLR) within a factor two of Sigma sub(SFR)~ 20 M sub(?) Gyr super(-1) pc super(-2). The dispersion in the Sigma sub(SFR)(R) profiles is significantly smaller in late type spirals (Sbc, Sc, Sd). This confirms that the MSSF is a sequence of galaxies with nearly constant Sigma sub(SFR). (b) sSFR values scale with Hubble type and increase radially outward with a steeper slope in the inner 1 HLR. This behavior suggests that galaxies are quenched inside-out and that this process is faster in the central, bulge-dominated part than in the disks. (c) As a whole and at all radii, E and S0 are off the MSSF with SFR much smaller than spirals of the same mass. (d) Applying the volume corrections for the CALIFA sample, we obtain a density of star formation in the local Universe of rho sub(SFR)= (0.0105 + or - 0.0008) M sub(?) yr super(-1) Mpc super(-3), in agreement with independent estimates. Most of the star formation is occurring in the disks of spirals. (e) The volume-averaged birthrate parameter, which measures the current SFR with respect to its lifetime average, b? = 0.39 + or - 0.03, suggests that the present day Universe is forming stars a about one-third of its past average rate. E, S0, and the bulge of early type spirals (Sa, Sb) contribute little to the recent SFRof the Universe, which is dominated by the disks of Sbc, Sc, and Sd spirals. (f) There is a tight relation between Sigma sub(SFR) and mu sub(*), defining a local MSSF relation with a logarithmic slope of 0.8, similar to the global MSSF relation between SFR and M sub(?). This suggests that local processes are important in determining the star formation in disks, probably through a density dependence of the SFR law. The scatter in the local MSSF is driven by morphology-related offsets, with Sigma sub(SFR)/mu sub(*)(the local sSFR) increasing from early to late type galaxies, indicating that the shut down of the star formation is more related to global processes, such as the formation of a spheroidal component.
Various different physical processes contribute to the star formation and stellar mass assembly histories of galaxies. One important approach to understanding the significance of these different ...processes on galaxy evolution is the study of the stellar population content of today's galaxies in a spatially resolved manner. The aim of this paper is to characterize in detail the radial structure of stellar population properties of galaxies in the nearby universe, based on a uniquely large galaxy sample, considering the quality and coverage of the data. The sample under study was drawn from the CALIFA survey and contains 300 galaxies observed with integral field spectroscopy. To study mean trends with overall galaxy properties, the individual radial profiles are stacked in seven bins of galaxy morphology (E, SO,Sa, Sb, Sbc, Sc, and Sd). The galaxies from the sample have decreasing-outward stellar extinction; all spirals show similar radial profiles, independent from the stellar mass, but redder than E and SO. Overall, we conclude that quenching processes act in manners that are independent of mass, while metallicity and galaxy structure are influenced by mass-dependent processes.
We present the apparent stellar angular momentum over the optical extent of 300 galaxies across the Hubble sequence using integral-field spectroscopic (IFS) data from the CALIFA survey. Adopting the ...same λR parameter previously used to distinguish between slow and fast rotating early-type (elliptical and lenticular) galaxies, we show that spiral galaxies are almost all fast rotators, as expected. Given the extent of our data, we provide relations for λR measured in different apertures (e.g. fractions of the effective radius: 0.5 Re, Re, 2 Re), including conversions to long-slit 1D apertures. Our sample displays a wide range of λRe values, consistent with previous IFS studies. The fastest rotators are dominated by relatively massive and highly star-forming Sb galaxies, which preferentially reside in the main star-forming sequence. These galaxies reach λRe values of ∼0.85, and they are the largest galaxies at a given mass, while also displaying some of the strongest stellar population gradients. Compared to the population of S0 galaxies, our findings suggest that fading may not be the dominant mechanism transforming spirals into lenticulars. Interestingly, we find that λRe decreases for late-type Sc and Sd spiral galaxies, with values that occasionally set them in the slow-rotator regime. While for some of them this can be explained by their irregular morphologies and/or face-on configurations, others are edge-on systems with no signs of significant dust obscuration. The latter are typically at the low-mass end, but this does not explain their location in the classical (V/σ, ε) and (λRe, ε) diagrams. Our initial investigations, based on dynamical models, suggest that these are dynamically hot disks, probably influenced by the observed important fraction of dark matter within Re.
We report on a detailed study of the stellar populations and ionized gas properties in the merger LIRG NGC 2623, analyzing optical integral field spectroscopy from the CALIFA survey and PMAS LArr, ...multiwavelength HST imaging, and OSIRIS narrow band Hα and NIIλ6584 imaging. The spectra were processed with the starlight full spectral fitting code, and the results are compared with those for two early-stage merger LIRGs (IC 1623 W and NGC 6090), together with CALIFA Sbc/Sc galaxies. We find that NGC 2623 went through two periods of increased star formation (SF), a first and widespread episode, traced by intermediate-age stellar populations ISP (140 Myr–1.4 Gyr), and a second one, traced by young stellar populations YSP (<140 Myr), which is concentrated in the central regions (<1.4 kpc). Our results are in agreement with the epochs of the first peri-center passage (~200 Myr ago) and coalescence (<100 Myr ago) predicted by dynamical models, and with high-resolution merger simulations in the literature, consistent with NGC 2623 representing an evolved version of the early-stage mergers. Most ionized gas is concentrated within <2.8 kpc, where LINER-like ionization and high-velocity dispersion (~220 km s-1) are found, consistent with the previously reported outflow. As revealed by the highest-resolution OSIRIS and HST data, a collection of HII regions is also present in the plane of the galaxy, which explains the mixture of ionization mechanisms in this system. It is unlikely that the outflow in NGC 2623 will escape from the galaxy, given the low SFR intensity (~0.5 M⊙ yr-1 kpc-2), the fact that the outflow rate is three times lower than the current SFR, and the escape velocity in the central areas is higher than the outflow velocity.
We use deep optical, infrared and radio observations to explore the symbiosis between nuclear activity and galaxy evolution in the southern compact radio source PKS 1549−79 (z= 0.1523). The optical ...imaging observations reveal the presence of tidal tail features which provide strong evidence that the host galaxy has undergone a major merger in the recent past. The merger hypothesis is further supported by the detection of a young stellar population (YSP), which, on the basis of spectral synthesis modelling of our deep Very Large Telescope (VLT) optical spectra, was formed 50-250 Myr ago and makes up a significant fraction of the total stellar mass (1-30 per cent). Despite the core-jet structure of the radio source, which is consistent with the idea that the jet is pointing close to our line of sight, our H i 21-cm observations reveal significant H i absorption associated with both the core and the jet. Moreover, the luminous, quasar-like active galactic nucleus (AGN) (MV
< −23.5) is highly extinguished (A
v
> 6.4) at optical wavelengths and show many properties in common with narrow-line Seyfert 1 galaxies (NLS1), including relatively narrow permitted lines full width at half-maximum (FWHM) ∼ 1940 km s−1, highly blueshifted O iiiλλ5007,4959 lines (ΔV∼ 680 km s−1) and evidence that the putative supermassive black hole is accreting at a high Eddington ratio (0.3 < L
bol/L
edd < 11). The results suggest that accretion at high Eddington ratio does not prevent the formation of powerful relativistic jets.
Together, the observations lend strong support to the predictions of some recent numerical simulations of galaxy mergers in which the black hole grows rapidly through merger-induced accretion following the coalescence of the nuclei of two merging galaxies, and the major growth phase is largely hidden at optical wavelengths by the natal gas and dust. Although the models also predict that AGN-driven outflows will eventually remove the gas from the bulge of the host galaxy, the visible warm outflow in PKS 1549−79 is not currently capable of doing so. However, much of the outflow may be hidden by the material obscuring the quasar and/or tied up in hotter or cooler phases of the interstellar medium.
By combining our estimates of the reddening of the quasar with the H i column derived from the 21-cm radio observations, we have also made the first direct estimate of the H i spin temperature in the vicinity of a luminous AGN: T
spin > 3000 K.
Aims. One of the main scientific drivers for ESPRESSO, Échelle SPectrograph, is the detection and characterization of Earth-class exoplanets. With this goal in mind, the ESPRESSO guaranteed time ...observations (GTO) Catalog identifies the best target stars for a blind search for the radial velocity (RV) signals caused by Earth-class exoplanets. Methods. Using the most complete stellar catalogs available, we screened for the most suitable G, K, and M dwarf stars for the detection of Earth-class exoplanets with ESPRESSO. For most of the stars, we then gathered high-resolution spectra from new observations or from archival data. We used these spectra to spectroscopically investigate the existence of any stellar binaries, both bound or background stars. We derived the activity level using chromospheric activity indexes using log (R′HK) $(R' _{\textrm{HK}})$ (RHK′) , as well as the projected rotational velocity v sin i. For the cases where planet companions are already known, we also looked at the possibility that additional planets may exist in the host’s habitable zone using dynamical arguments. Results. We estimated the spectroscopic contamination level, v sin i, activity, stellar parameters and chemical abundances for 249 of the most promising targets. Using these data, we selected 45 stars that match our criteria for detectability of a planet like Earth. The stars presented and discussed in this paper constitute the ESPRESSO GTO catalog for the RV blind search for Earth-class planets. They can also be used for any other work requiring a detailed spectroscopic characterization of stars in the solar neighborhood.
This is the second of two papers presenting a detailed long-slit spectroscopic study of the stellar populations in a sample of 36 ultraluminous infrared galaxies (ULIRGs). In the previous paper, we ...presented the sample, the data and the spectral synthesis modelling. In this paper, we carry out a more detailed analysis of the modelling results, with the aim of investigating the general properties of the stellar populations (i.e. age, reddening and percentage contribution) and the evolution of the host galaxies, comparing the results with other studies of ULIRGs and star-forming galaxies in the high-z Universe. The characteristic age of the young stellar populations (YSPs) is ≤100 Myr in the nuclei of the overwhelming majority of galaxies, consistent with the characteristic time-scale of the major burst of star formation (SF) associated with the final stages of major galaxy mergers. However, the modelling results clearly reveal that the SF histories of ULIRGs are complex, with at least two epochs of SF activity. Overall, these results are consistent with models that predict an epoch of enhanced SF coinciding with the first peri-centre passage of the merging nuclei, along with a further, more intense, episode of SF occurring as the nuclei finally merge together. It is also found that, although YSPs make a major contribution to the optical emission in most of the extended and nuclear apertures examined, they tend to be younger and more reddened in the nuclear regions of the galaxies. This is in good agreement with the merger simulations, which predict that the bulk of the SF activity in the final stages of mergers will occur in the nuclear regions of the merging galaxies. In addition, our results show that ULIRGs have total stellar masses that are similar to, or smaller than, the break of the galaxy mass function (i.e. ULIRGs are sub-m* or ∼m* systems), and that the YSPs detected at optical wavelengths dominate the stellar mass contents of the galaxies. Finally, we find no significant differences between the ages of the YSP in ULIRGs with and without optically detected Seyfert nuclei, nor between those with warm and cool mid- to far-IR colours. While these results do not entirely rule out the idea that cool ULIRGs with H ii/LINER spectra evolve into warm ULIRGs with Seyfert-like spectra, it is clear that the active galactic nucleus (AGN) activity in local Seyfert-like ULIRGs has not been triggered for a substantial period (≥100 Myr) after the major merger-induced starbursts in the nuclear regions.
We present an extended version of the spectral synthesis code starlight designed to incorporate both λ-by-λ spectra and photometric fluxes in the estimation of stellar population properties of ...galaxies. The code is tested with simulations and data for 260 galaxies culled from the Calar Alto Legacy Integral Field Area (CALIFA) survey, spatially matching the 3700–7000 Å optical data cubes to Galaxy Evolution Explorer (GALEX) near-ultraviolet (NUV) and far-ultraviolet (FUV) images. The sample spans E–Sd galaxies with masses from 109 to 1012 M⊙ and stellar populations all the way from star-forming to old, passive systems. Comparing results derived from purely optical fits with those which also consider the NUV and FUV data we find that the following. (1) The new code is capable of matching the input ultraviolet (UV) data within the errors while keeping the quality of the optical fit essentially unchanged. (2) Despite being unreliable predictors of the UV fluxes, purely optical fits yield stellar population properties which agree well with those obtained in optical+UV fits for nearly 90 per cent of our sample. (3) The addition of UV constraints has little impact on properties such as stellar mass and dust optical depth. Mean stellar ages and metallicities also remain nearly the same for most galaxies, the exception being low-mass, late-type galaxies, which become older and less enriched due to rearrangements of their youngest populations. (4) The revised ages are better correlated with observables such as the 4000 Å break index, and the NUV − r and u − r colours, an empirical indication that the addition of UV constraints helps mitigating the effects of age–metallicity–extinction degeneracies.
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