Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe Large Early Galaxy Astrophysics Census (LEGA-C) Data Release II: dynamical and stellar population properties of z ~< 1 galaxies in the COSMOS field
167
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present the second data release of the Large Early Galaxy Astrophysics Census (LEGA-C), an ESO 130-night public spectroscopic survey conducted with VIMOS on the Very Large Telescope. We release 1988 spectra with typical continuum S / N ~= 20 /Angstrom of galaxies at 0.6 ~< z ~< 1.0, each observed for ~20 hours and fully reduced with a custom-built pipeline. We also release a catalog with spectroscopic redshifts, emission line fluxes, Lick/IDS indices, and observed stellar and gas velocity dispersions that are spatially integrated quantities including both rotational motions and genuine dispersion. To illustrate the new parameter space in the intermediate redshift regime probed by LEGA-C we explore relationships between dynamical and stellar population properties. The star-forming galaxies typically have observed stellar velocity dispersions of ~150 km/s and strong Hdelta absorption (Hd_A ~ 5 Angstrom), while passive galaxies have higher observed stellar velocity dispersions ~200 km/s and weak Hdelta absortion (Hd_A ~ 0 Angstrom). Strong [O III]5007 / Hbeta ratios tend to occur mostly for galaxies with weak Hd_A or galaxies with higher observed velocity dispersion. Beyond these broad trends, we find a large diversity of possible combinations of rest-frame colors, absorption line strengths and emission line detections, illustrating the utility of spectroscopic measurements to more accurately understand galaxy evolution. By making the spectra and value-added catalogs publicly available we encourage the community to take advantage of this very substantial investment in telescope time provided by ESO.
rate research
Read More
We present the third and final data release of the Large Early Galaxy Astrophysics Census (LEGA-C), an ESO/VLT public spectroscopic survey targeting $0.6 < z < 1.0$, Ks-selected galaxies. The data release contains 3528 spectra with measured stellar velocity dispersions and stellar population properties, a 25-fold increase in sample size compared to previous work. This $K_s$-selected sample probes the galaxy population down to $sim0.3 L^*$, for all colors and morphological types. Along with the spectra we publish a value-added catalog with stellar and ionized gas velocity dispersions, stellar absorption line indices, emission line fluxes and equivalent widths, complemented with structural parameters measured from HST/ACS imaging. With its combination of high precision and large sample size, LEGA-C provides a new benchmark for galaxy evolution studies.
We use deep, spatially resolved spectroscopy from the LEGA-C Survey to study radial variations in the stellar population of 17 spectroscopically-selected post-starburst (PSB) galaxies. We use spectral fitting to measure two Lick indices, $H{delta}_A$ and $Fe4383$, and find that, on average, PSB galaxies have radially decreasing $H{delta}_A$ and increasing $Fe4383$ profiles. In contrast, a control sample of quiescent, non-PSB galaxies in the same mass range shows outwardly increasing $H{delta}_A$ and decreasing $Fe4383$. The observed gradients are weak ($approx-0.2$ r{A}/$R_e$), mainly due to seeing convolution. A two-SSP model suggests intrinsic gradients are as strong as observed in local PSB galaxies ($approx -0.8$ r{A}$/R_e$). We interpret these results in terms of inside-out growth (for the bulk of the quiescent population) vs star formation occurring last in the centre (for PSB galaxies). At $zapprox0.8$, central starbursts are often the result of gas-rich mergers, as evidenced by the high fraction of PSB galaxies with disturbed morphologies and tidal features (40%). Our results provide additional evidence for multiple paths to quiescence: a standard path, associated with inside-out disc formation and with gradually decreasing star-formation activity, without fundamental structural transformation, and a fast path, associated with centrally-concentrated starbursts, leaving an inverse age gradient and smaller half-light radius.
Measuring redshifted CO line emission is an unambiguous method for obtaining an accurate redshift and total cold gas content of optically faint, dusty starburst systems. Here, we report the first successful spectroscopic redshift determination of AzTEC J095942.9+022938 (COSMOS AzTEC-1), the brightest 1.1mm continuum source found in the AzTEC/JCMT survey (Scott et al. 2008), through a clear detection of the redshifted CO (4-3) and CO (5-4) lines using the Redshift Search Receiver on the Large Millimeter Telescope. The CO redshift of $z=4.3420pm0.0004$ is confirmed by the detection of the redshifted 158 micron [C II] line using the Submillimeter Array. The new redshift and Herschel photometry yield $L_{FIR}=(1.1pm0.1)times 10^{13} L_odot$ and $SFR = 1300, M_odot$ yr$^{-1}$. Its molecular gas mass derived using the ULIRG conversion factor is $1.4pm0.2 times 10^{11} M_odot$ while the total ISM mass derived from the 1.1mm dust continuum is $3.7pm0.7 times 10^{11} M_odot$ assuming dust temperature of 35 K. Our dynamical mass analysis suggests that the compact gas disk ($rapprox 1.1$ kpc, inferred from dust continuum and SED analysis) has to be nearly face-on, providing a natural explanation for the uncommonly bright, compact stellar light seen by the HST. The [C II] line luminosity $L_{[C~II]} = 7.8pm1.1 times 10^9 L_odot$ is remarkably high, but it is only 0.04 per cent of the total IR luminosity. AzTEC COSMOS-1 and other high redshift sources with a spatially resolved size extend the tight trend seen between [C II]/FIR ratio and $Sigma_{FIR}$ among IR-bright galaxies reported by Diaz-Santos et al. (2013) by more than an order of magnitude, supporting the explanation that the higher intensity of the IR radiation field is responsible for the [C II] deficiency seen among luminous starburst galaxies.
We present spatially resolved stellar kinematics for 797 $z=0.6-1$ galaxies selected from the LEGA-C survey and construct axisymmetric Jeans models to quantify their dynamical mass and degree of rotational support. The survey is $K_s$-band selected, irrespective of color or morphological type, and allows for a first assessment of the stellar dynamical structure of the general $L^*$ galaxy population at large lookback time. Using light profiles from Hubble Space Telescope imaging as a tracer, our approach corrects for observational effects (seeing convolution and slit geometry), and uses well-informed priors on inclination, anisotropy and a non-luminous mass component. Tabulated data include total mass estimates in a series of spherical apertures (1, 5, and 10 kpc; 1$times$ and 2$times$re), as well as rotational velocities, velocity dispersions and anisotropy. We show that almost all star-forming galaxies and $sim$50% of quiescent galaxies are rotation-dominated, with deprojected $V/sigmasim1-2$. Revealing the complexity in galaxy evolution, we find that the most massive star-forming galaxies are among the most rotation-dominated, and the most massive quiescent galaxies among the least rotation-dominated galaxies. These measurements set a new benchmark for studying galaxy evolution, using stellar dynamical structure for galaxies at large lookback time. Together with the additional information on stellar population properties from the LEGA-C spectra, the dynamical mass and $V/sigma$ measurements presented here create new avenues for studying galaxy evolution at large lookback time.
We present the first data release (DR1) of the VST Early-type GAlaxy Survey (VEGAS). This is a deep multi-band (ugri) imaging survey, carried out with the ESO VLT Survey Telescope (VST). To date, using about 90% of the total observing time, VEGAS has already collected 43 targets (groups and clusters of galaxies) covering a total area on the sky of about 95 square degrees. Taking advantage of the wide (1 deg^2) field-of-view of OmegaCAM@VST, the long integration time and the wide variety of targets, VEGAS has proven to be a gold mine to explore the structure of galaxies down to the faintest surface brightness levels of about 27-30 mag/arcsec^2 in the SDSS g band, for the dense clusters of galaxies and for the unexplored poor groups of galaxies. Based on the analysed data, VEGAS allowed us to i) study the galaxy outskirts, detect the intra-cluster light and low-surface brightness features in the intra-cluster/group space, ii) trace the mass assembly in galaxies, by estimating the accreted mass fraction in the stellar halos and provide results that can be directly compared with the predictions of galaxy formation models, iii) trace the spatial distribution of candidate globular clusters, and iv) detect the ultra-diffuse galaxies. With the DR1, we provide the reduced VST mosaics of 10 targets, which have been presented in the VEGAS publications. The data products are available via the ESO Science Portal (see http://www.eso.org/sci/observing/phase3/news.html#VEGAS-DR1).
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
