ABSTRACT
We explore how the star formation and metal enrichment histories of present-day galaxies have been affected by environment combining stellar population parameter estimates and group ...environment characterization for SDSS DR7. We compare stellar ages, stellar metallicities, and crucially, element abundance ratios $\rm \alpha /Fe$ of satellite and central galaxies, as a function of their stellar and host group halo mass, controlling for the current star formation rate and for the infall epoch. We confirm that below M* ∼ 1010.5 M⊙ satellites are older and slightly metal richer than equally massive central galaxies. In contrast, we do not detect any difference in their $\rm \alpha /Fe$: $\rm \alpha /Fe$ depends primarily on stellar mass and not on group hierarchy nor host halo mass. We also find that the differences in the median age and metallicity of satellites and centrals at stellar mass below $\rm 10^{10.5}\,M_\odot$ are largely due to the higher fraction of passive galaxies among satellites and as a function of halo mass. We argue that the observed trends at low masses reveal the action of satellite-specific environmental effects in a ‘delayed-then-rapid’ fashion. When accounting for the varying quiescent fraction, small residual excess in age, metallicity and $\rm \alpha /Fe$ emerge for satellites dominated by old stellar populations and residing in haloes more massive than 1014 M⊙, compared to equally massive central galaxies. This excess in age, metallicity, and $\rm \alpha /Fe$ pertain to ancient infallers, i.e. satellites that have accreted on to the current halo more than 5 Gyr ago. This result points to the action of environment in the early phases of star formation in galaxies located close to cosmic density peaks.
ABSTRACT The "main sequence of galaxies"-defined in terms of the total star formation rate versus the total stellar mass M*-is a well-studied tight relation that has been observed at several ...wavelengths and at different redshifts. All earlier studies have derived this relation from integrated properties of galaxies. We recover the same relation from an analysis of spatially resolved properties, with integral field spectroscopic (IFS) observations of 306 galaxies from the CALIFA survey. We consider the SFR surface density in units of log(M yr−1 Kpc−2) and the stellar mass surface density in units of log(M Kpc−2) in individual spaxels that probe spatial scales of 0.5-1.5 Kpc. This local relation exhibits a high degree of correlation with small scatter ( = 0.23 dex), irrespective of the dominant ionization source of the host galaxy or its integrated stellar mass. We highlight (i) the integrated star formation main sequence formed by galaxies whose dominant ionization process is related to star formation, for which we find a slope of 0.81 0.02; (ii) for the spatially resolved relation obtained with the spaxel analysis, we find a slope of 0.72 0.04; and (iii) for the integrated main sequence, we also identified a sequence formed by galaxies that are dominated by an old stellar population, which we have called the retired galaxies sequence.
We investigate how environment affects satellite galaxies using their location within the projected phase space of their host haloes from the Wang et al.'s group catalogue. Using the Yonsei Zoom-in ...Cluster Simulations, we derive zones of constant mean infall time \overline{T}_inf in projected phase space, and catalogue in which zone each observed galaxy falls. Within each zone, we compute the mean observed galaxy properties including specific star formation rate, luminosity-weighted age, stellar metallicity, and α/Fe abundance ratio. By comparing galaxies in different zones, we inspect how shifting the mean infall time from recent infallers (\overline{T}_inf < 3 Gyr) to ancient infallers (\overline{T}_{inf}> 5 Gyr) impacts galaxy properties at fixed stellar and halo mass. Ancient infallers are more quenched, and the impact of environmental quenching is visible down to low host masses (≤group masses). Meanwhile, the quenching of recent infallers is weakly dependent on host mass, indicating they have yet to respond strongly to their current environment. α/Fe and especially metallicity are less dependent on host mass, but show a dependence on \overline{T}_{inf}. We discuss these results in the context of longer exposure times for ancient infallers to environmental effects, which grow more efficient in hosts with a deeper potential well and a denser intracluster medium. We also compare our satellites with a control field sample, and find that even the most recent infallers (\overline{T}_{inf} < 2 Gyr) are more quenched than field galaxies, in particular for cluster mass hosts. This supports the role of pre-processing and/or faster quenching in satellites.
We investigated the interstellar medium (ISM) properties of the disc and outflowing gas in the central regions of nine nearby Seyfert galaxies, all characterised by prominent conical or biconical ...outflows. These objects are part of the Measuring Active Galactic Nuclei Under MUSE Microscope (MAGNUM) survey, which aims to probe their physical conditions and ionisation mechanism by exploiting the unprecedented sensitivity of the Multi Unit Spectroscopic Explorer (MUSE), combined with its spatial and spectral coverage. Specifically, we studied the different properties of the gas in the disc and in the outflow with spatially and kinematically resolved maps by dividing the strongest emission lines in velocity bins. We associated the core of the lines with the disc, consistent with the stellar velocity, and the redshifted and the blueshifted wings with the outflow. We measured the reddening, density, ionisation parameter, and dominant ionisation source of the emitting gas for both components in each galaxy. We find that the outflowing gas is characterised by higher values of density and ionisation parameter than the disc, which presents a higher dust extinction. Moreover, we distinguish high- and low-ionisation regions across the portion of spatially resolved narrow-line region (NLR) traced by the outflowing gas. The high-ionisation regions characterised by the lowest N II/Hα and S II/Hα line ratios generally trace the innermost parts along the axis of the emitting cones where the S III/S II line ratio is enhanced, while the low-ionisation regions follow the cone edges and/or the regions perpendicular to the axis of the outflows, also characterised by a higher O III velocity dispersion. A possible scenario to explain these features relies on the presence of two distinct populations of line emitting clouds: one is optically thin to the radiation and is characterised by the highest excitation, while the other is optically thick and is impinged by a filtered, and thus harder, radiation field which generates strong low-excitation lines. The highest values of N II/Hα and S II/Hα line ratios may be due to shocks and/or a hard filtered radiation field from the active galactic nucleus.
We study the ionization and kinematics of the ionized gas in the nuclear region of the barred Seyfert 2 galaxy NGC 5643 using MUSE integral field observations in the framework of the Measuring Active ...Galactic Nuclei Under MUSE Microscope (MAGNUM) survey. The data were used to identify regions with different ionization conditions and to map the gas density and the dust extinction. We find evidence for a double-sided ionization cone, possibly collimated by a dusty structure surrounding the nucleus. At the center of the ionization cone, outflowing ionized gas is revealed as a blueshifted, asymmetric wing of the OIII emission line, up to projected velocity v10 ~ −450 km s-1. The outflow is also seen as a diffuse, low-luminosity radio and X-ray jet, with similar extension. The outflowing material points in the direction of two clumps characterized by prominent line emission with spectra typical of HII regions, located at the edge of the dust lane of the bar. We propose that the star formation in the clumps is due to positive feedback induced by gas compression by the nuclear outflow, providing the first candidate for outflow-induced star formation in a Seyfert-like, radio-quiet AGN. This suggests that positive feedback may be a relevant mechanism in shaping the black hole-host galaxy coevolution.
This paper describes the third public data release (DR3) of the Calar Alto Legacy Integral Field Area (CALIFA) survey. Science-grade quality data for 667 galaxies are made public, including the 200 ...galaxies of the second public data release (DR2). Data were obtained with the integral-field spectrograph PMAS/PPak mounted on the 3.5 m telescope at the Calar Alto Observatory. Three different spectral setups are available: i) a low-resolution V500 setup covering the wavelength range 3745-7500 A (4240-7140 A unvignetted) with a spectral resolution of 6.0 A (FWHM) for 646 galaxies, ii) a medium-resolution V1200 setup covering the wavelength range 3650-4840 A (3650-4620 A unvignetted) with a spectral resolution of 2.3 A (FWHM) for 484 galaxies, and iii) the combination of the cubes from both setups (called COMBO) with a spectral resolution of 6.0 A and a wavelength range between 3700-7500 A (3700-7140 A unvignetted) for 446 galaxies. The Main Sample, selected and observed according to the CALIFA survey strategy covers a redshift range between 0.005 and 0.03, spans the color-magnitude diagram and probes a wide range of stellar masses, ionization conditions, and morphological types. The Extension Sample covers several types of galaxies that are rare in the overall galaxy population and are therefore not numerous or absent in the CALIFA Main Sample. All the cubes in the data release were processed using the latest pipeline, which includes improved versions of the calibration frames and an even further improved image reconstruction quality. In total, the third data release contains 1576 datacubes, including ~1.5 million independent spectra.
The mass–metallicity relation revisited with CALIFA Sánchez, S. F.; Barrera-Ballesteros, J. K.; Sánchez-Menguiano, L. ...
Monthly notices of the Royal Astronomical Society,
08/2017, Letnik:
469, Številka:
2
Journal Article
We derive photometric redshifts from 17-band optical to mid-infrared photometry of 78 robust radio, 24-μm and Spitzer IRAC counterparts to 72 of the 126 submillimetre galaxies (SMGs) selected at 870 ...μm by LABOCA observations in the Extended Chandra Deep Field-South (ECDF-S). We test the photometric redshifts of the SMGs against the extensive archival spectroscopy in the ECDF-S. The median photometric redshift of identified SMGs is z= 2.2 ± 0.1, the standard deviation is σ
z
= 0.9 and we identify 11 (∼15 per cent) high-redshift (z≥ 3) SMGs. A statistical analysis of sources in the error circles of unidentified SMGs identifies a population of possible counterparts with a redshift distribution peaking at z= 2.5 ± 0.2, which likely comprises ∼60 per cent of the unidentified SMGs. This confirms that the bulk of the undetected SMGs are coeval with those detected in the radio/mid-infrared. We conclude that at most ∼15 per cent of all the SMGs are below the flux limits of our IRAC observations and thus may lie at z≳ 3 and hence at most ∼30 per cent of all SMGs have z≳ 3. We estimate that the full S
870 μm > 4 mJy SMG population has a median redshift of 2.5 ± 0.5. In contrast to previous suggestions, we find no significant correlation between submillimetre flux and redshift. The median stellar mass of the SMGs derived from spectral energy distribution fitting is (9.1 ± 0.5) × 1010 M⊙ although we caution that the uncertainty in the star formation histories results in a factor of ∼5 uncertainty in these stellar masses. Using a single temperature modified blackbody fit with β= 1.5, the median characteristic dust temperature of SMGs is 37.4 ± 1.4 K. The infrared luminosity function shows that SMGs at z= 2-3 typically have higher far-infrared luminosities and luminosity density than those at z= 1-2. This is mirrored in the evolution of the star formation rate density (SFRD) for SMGs which peaks at z∼ 2. The maximum contribution of bright SMGs to the global SFRD (∼5 per cent for SMGs with S
870 μm≳ 4 mJy or ∼50 per cent extrapolated to SMGs with S
870 μm > 1 mJy) also occurs at z∼ 2.
We study the dynamics of faint stellar substructures around the Umbrella Galaxy, NGC 4651, which hosts a dramatic system of streams and shells formed through the tidal disruption of a nucleated dwarf ...elliptical galaxy. We elucidate the basic characteristics of the system (colours, luminosities, stellar masses) using multiband Subaru/Suprime-Cam images. The implied stellar mass ratio of the ongoing merger event is ∼1:50. We identify candidate kinematic tracers (globular clusters, planetary nebulae, H ii regions) and follow up a subset with Keck/DEIMOS (DEep Imaging Multi-object Spectrograph) spectroscopy to obtain velocities. We find that 15 of the tracers are likely associated with halo substructures, including the probable stream progenitor nucleus. These objects delineate a kinematically cold feature in position–velocity phase space. We model the stream using single test particle orbits, plus a rescaled pre-existing N-body simulation. We infer a very eccentric orbit with a period of ∼0.35 Gyr and turning points at ∼2–4 and ∼40 kpc, implying a recent passage of the satellite through the disc, which may have provoked the visible disturbances in the host galaxy. This work confirms that the kinematics of low surface brightness substructures can be recovered and modelled using discrete tracers – a breakthrough that opens up a fresh avenue for unravelling the detailed physics of minor merging.
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.
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