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1951. LEDA CMD/tip of the red giant branch
ID:
ivo://CDS.VizieR/J/AJ/138/332
Title:
LEDA CMD/tip of the red giant branch
Short Name:
J/AJ/138/332
Date:
21 Oct 2021
Publisher:
CDS
Description:
The color-magnitude diagrams/tip of the red giant branch (CMDs/TRGB) section of the Extragalactic Distance Database contains a compilation of observations of nearby galaxies from the Hubble Space Telescope. Approximately 250 (and increasing) galaxies in the Local Volume have CMDs and the stellar photometry tables used to produce them available through the Web. Various stellar populations that make up a galaxy are visible in the CMDs, but our primary purpose for collecting and analyzing these galaxy images is to measure the TRGB in each. We can estimate the distance to a galaxy by using stars at the TRGB as standard candles. In this paper, we describe the process of constructing the CMDs and make the results available to the public.
1952. LEDA galaxies with DENIS measurements catalog
ID:
ivo://CDS.VizieR/VII/242
Title:
LEDA galaxies with DENIS measurements catalog
Short Name:
VII/242
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of near-infrared properties of LEDA galaxies, using the full resolution images from the DENIS survey. The fluxes are integrated in eight homothetic ellipses defined by their proper axis ratio, position angle and major axis (up to twice the blue diameter at the isophote 25mag/arcsec^2^) extracted from the LEDA database. From the curves of growth in I, J and K_ms_ photometric bands, we estimated different apparent magnitudes and diameters ("total", "Kron" and "isophotal"). Isophotal parameters refer to the limiting surface brightnesses : 22.5(Imag)/arcsec^2^, 21.0(Jmag)/arcsec^2^ and 20.0(K_ms_mag)/arcsec^2^ for the three photometric bands, respectively. The result is a catalog of 753 153 objects (among which there are 508 224 galaxies, 34 449 probable galaxies and 210 480 galaxies to be confirmed). The catalog gives about (the figures vary, depending on the considered magnitude or diameter) : 668 000 I-band magnitudes, 576 000 J-band magnitudes, 357 000 K_ms_-band magnitudes and 452 000 I-band diameters, 299 000 J-band diameters, 114 000 K_ms_-band diameters. The typical standard deviations for I, J and K_ms_ magnitudes are 0.14, 0.15 and 0.25, respectively, for magnitudes limited at I=16, J=15 and K_ms_=14. The contamination by superimposed objects probably remains the major source of problems and could require future improvement. The completeness limits in magnitude are about : 15.5, 14.5 and 13 in I, J and K_ms_, respectively.
1953. LEGA-C DR2: galaxies in the COSMOS field
ID:
ivo://CDS.VizieR/J/ApJS/239/27
Title:
LEGA-C DR2: galaxies in the COSMOS field
Short Name:
J/ApJS/239/27
Date:
01 Mar 2022
Publisher:
CDS
Description:
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{AA}^-1^ of galaxies at 0.6<~z<~1.0, each observed for ~20hr 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 ~150km/s and strong H{delta} absorption (H{delta}_A_~5{AA}), while passive galaxies have higher observed stellar velocity dispersions (~200km/s) and weak H{delta} absorption (H{delta}_A_~0{AA}). Strong [OIII]5007/H{beta} ratios tend to occur mostly for galaxies with weak H{delta}_A_ or galaxies with higher observed velocity dispersion. Beyond these broad trends, we find a 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.
1954. LEGUS galaxies1 observations
ID:
ivo://CDS.VizieR/J/ApJS/235/23
Title:
LEGUS galaxies1 observations
Short Name:
J/ApJS/235/23
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Legacy ExtraGalactic UV Survey (LEGUS) is a multiwavelength Cycle 21 Treasury program on the Hubble Space Telescope. It studied 50 nearby star-forming galaxies in 5 bands from the near-UV to the I-band, combining new Wide Field Camera 3 observations with archival Advanced Camera for Surveys data. LEGUS was designed to investigate how star formation occurs and develops on both small and large scales, and how it relates to the galactic environments. In this paper we present the photometric catalogs for all the apparently single stars identified in the 50 LEGUS galaxies. We present optical and near-UV color-magnitude diagrams for all the galaxies. For each galaxy we derived the distance from the tip of the red giant branch. We then used the NUV color-magnitude diagrams to identify stars more massive than 14M_{sun}_, and compared their number with the number of massive stars expected from the GALEX FUV luminosity. Our analysis shows that the fraction of massive stars forming in star clusters and stellar associations is about constant with the star formation rate. This lack of a relation suggests that the timescale for evaporation of unbound structures is comparable or longer than 10Myr. At low star formation rates this translates to an excess of mass in clustered environments as compared to model predictions of cluster evolution, suggesting that a significant fraction of stars form in unbound systems.
1955. LEGUS & Ha-LEGUS obs. of NGC4449 star clusters
ID:
ivo://CDS.VizieR/J/ApJ/889/154
Title:
LEGUS & Ha-LEGUS obs. of NGC4449 star clusters
Short Name:
J/ApJ/889/154
Date:
17 Jan 2022 11:55:48
Publisher:
CDS
Description:
We present a new catalog and results for the cluster system of the starburst galaxy NGC 4449, based on multiband imaging observations taken as part of the LEGUS and H_{alpha}_-LEGUS surveys. We improve the spectral energy fitting method used to estimate cluster ages, and find that the results, particularly for older clusters, are in better agreement with those from spectroscopy. The inclusion of H{alpha} measurements, the role of stochasticity for low-mass clusters, the assumptions about reddening, and the choices of SSP model and metallicity all have important impacts on the age dating of clusters. A comparison with ages derived from stellar color-magnitude diagrams for partially resolved clusters shows reasonable agreement, but large scatter in some cases. The fraction of light found in clusters relative to the total light (i.e., T_L_) in the U, B, and V filters in 25 different ~kiloparsec-size regions throughout NGC 4449 correlates with both the specific region luminosity, R_L_, and the dominant age of the underlying stellar population in each region. The observed cluster age distribution is found to decline over time as dN/d{tau}{propto}{tau}^{gamma}^, with {gamma}=-0.85+/-0.15, independent of cluster mass, and is consistent with strong, early cluster disruption. The mass functions of the clusters can be described by a power law with dN/dM{propto}M^{beta}^ and {beta}=-1.86+/-0.2, independent of cluster age. The mass and age distributions are quite resilient to differences in age-dating methods. There is tentative evidence for a factor of 2-3 enhancement in both the star and cluster formation rate ~100-300Myr ago, indicating that cluster formation tracks star formation generally. The enhancement is probably associated with an earlier interaction event.
1956. Lensed z~6-8 galaxies behind CLASH clusters
ID:
ivo://CDS.VizieR/J/ApJ/792/76
Title:
Lensed z~6-8 galaxies behind CLASH clusters
Short Name:
J/ApJ/792/76
Date:
21 Oct 2021
Publisher:
CDS
Description:
We utilize 16 band Hubble Space Telescope (HST) observations of 18 lensing clusters obtained as part of the Cluster Lensing And Supernova survey with Hubble (CLASH) Multi-Cycle Treasury program to search for z ~ 6-8 galaxies. We report the discovery of 204, 45, and 13 Lyman-break galaxy candidates at z ~ 6, z ~ 7, and z ~ 8, respectively, identified from purely photometric redshift selections. This large sample, representing nearly an order of magnitude increase in the number of magnified star-forming galaxies at z ~ 6-8 presented to date, is unique in that we have observations in four WFC3/UVIS UV, seven ACS/WFC optical, and all five WFC3/IR broadband filters, which enable very accurate photometric redshift selections. We construct detailed lensing models for 17 of the 18 clusters to estimate object magnifications and to identify two new multiply lensed z >~ 6 candidates. The median magnifications over the 17 clusters are 4, 4, and 5 for the z ~ 6, z ~ 7, and z ~ 8 samples, respectively, over an average area of 4.5 arcmin^2^ per cluster. We compare our observed number counts with expectations based on convolving "blank" field UV luminosity functions through our cluster lens models and find rough agreement down to ~27 mag, where we begin to suffer significant incompleteness. In all three redshift bins, we find a higher number density at brighter observed magnitudes than the field predictions, empirically demonstrating for the first time the enhanced efficiency of lensing clusters over field surveys. Our number counts also are in general agreement with the lensed expectations from the cluster models, especially at z ~ 6, where we have the best statistics.
1957. Leo II stellar kinematics
ID:
ivo://CDS.VizieR/J/AJ/134/566
Title:
Leo II stellar kinematics
Short Name:
J/AJ/134/566
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the projected velocity dispersion profile for the remote (d=233kpc) Galactic dwarf spheroidal (dSph) galaxy Leo II, based on 171 discrete stellar radial velocities that were obtained from medium-resolution spectroscopy using the FLAMES/GIRAFFE spectrograph at the European Southern Observatory, Chile.
1958. Leo IV g- and r-band photometry
ID:
ivo://CDS.VizieR/J/ApJ/718/530
Title:
Leo IV g- and r-band photometry
Short Name:
J/ApJ/718/530
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present MMT/Megacam imaging of the Leo IV dwarf galaxy in order to investigate its structure and star formation history, and to search for signs of association with the recently discovered Leo V satellite. Based on parameterized fits, we find that Leo IV is round, with {epsilon}<0.23 (at the 68% confidence limit) and a half-light radius of r_h_~130pc. Additionally, we perform a thorough search for extended structures in the plane of the sky and along the line of sight. We derive our surface brightness detection limit by implanting fake structures into our catalog with stellar populations identical to that of Leo IV. We show that we are sensitive to stream-like structures with surface brightness {mu}_r_<~29.6mag/arcsec^2^, and at this limit we find no stellar bridge between Leo IV (out to a radius of ~0.5kpc) and the recently discovered, nearby satellite Leo V. Using the color-magnitude fitting package StarFISH, we determine that Leo IV is consistent with a single age (~14Gyr), single metallicity ([Fe/H]~-2.3) stellar population, although we cannot rule out a significant spread in these values. We derive a luminosity of M_V_=-5.5+/-0.3. Studying both the spatial distribution and frequency of Leo IV's "blue plume" stars reveals evidence for a young (~2Gyr) stellar population which makes up ~2% of its stellar mass.
1959. Leo I VI photometry
ID:
ivo://CDS.VizieR/J/MNRAS/354/708
Title:
Leo I VI photometry
Short Name:
J/MNRAS/354/708
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present V and I photometry of a 9.4'x9.4' field centered on the dwarf spheroidal galaxy Leo I. The I magnitude of the tip of the Red Giant Branch is robustly estimated from two different datasets I^TRGB^=17.97 (^+0.05^_-0.03_). From this estimate, adopting [M/H]~-1.2 from the comparison of RGB stars with Galactic templates, we obtain a distance modulus (m-M)_0=22.02+/-0.13, corresponding to a distance D=254^+16^_-19_kpc.
1960. Leo P RR Lyrae candidates & cumulative SFH
ID:
ivo://CDS.VizieR/J/ApJ/812/158
Title:
Leo P RR Lyrae candidates & cumulative SFH
Short Name:
J/ApJ/812/158
Date:
21 Oct 2021
Publisher:
CDS
Description:
Leo P is a low-luminosity dwarf galaxy discovered through the blind HI Arecibo Legacy Fast ALFA survey. The HI and follow-up optical observations have shown that Leo P is a gas-rich dwarf galaxy with active star formation, an underlying older population, and an extremely low oxygen abundance. We have obtained optical imaging with the Hubble Space Telescope to two magnitudes below the red clump in order to study the evolution of Leo P. We refine the distance measurement to Leo P to be 1.62+/-0.15Mpc, based on the luminosity of the horizontal branch stars and 10 newly identified RR Lyrae candidates. This places the galaxy at the edge of the Local Group, ~0.4Mpc from Sextans B, the nearest galaxy in the NGC 3109 association of dwarf galaxies of which Leo P is clearly a member. The star responsible for ionizing the HII region is most likely an O7V or O8V spectral type, with a stellar mass >~25M_{sun}_. The presence of this star provides observational evidence that massive stars at the upper end of the initial mass function are capable of being formed at star formation rates as low as ~10^-5^M_{sun}_/yr. The best-fitting star formation history (SFH) derived from the resolved stellar populations of Leo P using the latest PARSEC models shows a relatively constant star formation rate over the lifetime of the galaxy. The modeled luminosity characteristics of Leo P at early times are consistent with low-luminosity dSph Milky Way satellites, suggesting that Leo P is what a low-mass dSph would look like if it evolved in isolation and retained its gas. Despite the very low mass of Leo P, the imprint of reionization on its SFHIs subtle at best, and consistent with being totally negligible. The isolation of Leo P, and the total quenching of star formation of Milky Way satellites of similar mass, implies that the local environment dominates the quenching of the Milky Way satellites.