- ID:
- ivo://CDS.VizieR/J/A+A/577/A81
- Title:
- Deep SDSS Optical Spectroscopy. II.
- Short Name:
- J/A+A/577/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze a sample of 3942 low-resolution (R~2000) optical spectra from the Sloan Digital Sky Survey (SDSS), focusing on stars with effective temperatures 5800<Teff<6300K, and distances from the Milky Way plane in excess of 5kpc, and determine their abundances of Fe, Ca, and Mg. This work follows the same methodology as in the previous paper in this series, deriving atmospheric parameters by chi^2^ minimization, but we now obtain the abundances of individual elements by fitting their associated spectral lines. Distances are calculated from absolute magnitudes obtained by a statistical comparison of our stellar parameters with stellar-evolution models. The observations reveal a decrease in the abundances of iron, calcium and magnesium at large distances from the Galactic center. The median abundances for the halo stars analyzed are fairly constant up to a Galactocentric distance r~20kpc, rapidly decrease between r~20 and r~40kpc, and flatten out to significantly lower values at larger distances, consistent with previous studies. In addition, we examine the Ca/Fe and Mg/Fe ratios as a function of Fe/H and Galactocentric distance. Our results show that the most distant parts of the halo show a steeper variation of the Ca/Fe and Mg/Fe with iron. We found that at the range -1.6<[Fe/H]<-0.4 the Ca/Fe ratio decreases with distance, in agreement with earlier results based on local stars. However, the opposite trend is apparent for Mg/Fe. Our conclusion that the outer regions of the halo are more metal-poor than the inner regions, based on in-situ observations of distant stars, is in concert with recent results based on inferences from the kinematics of more local stars, and with predictions of recent galaxy formation simulations for galaxies similar to the Milky Way.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/741/115
- Title:
- Deep spectroscopy in the GOODS fields
- Short Name:
- J/ApJ/741/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new measures of the evolving scaling relations between stellar mass, luminosity and rotational velocity for a morphologically inclusive sample of 129 disk-like galaxies with z_AB_<22.5 in the redshift range 0.2<z<1.3, based on spectra from DEep Imaging Multi-Object Spectrograph on the Keck II telescope, multi-color Hubble Space Telescope (HST) Advanced Camera for Surveys photometry, and ground-based Ks-band imaging. A unique feature of our survey is the extended spectroscopic integration times, leading to significant improvements in determining characteristic rotational velocities for each galaxy. Rotation curves are reliably traced to the radius where they begin to flatten for ~90% of our sample, and we model the HST-resolved bulge and disk components in order to accurately de-project our measured velocities, accounting for seeing and dispersion. We demonstrate the merit of these advances by recovering an intrinsic scatter on the stellar mass Tully-Fisher relation a factor of two to three less than in previous studies at intermediate redshift and comparable to that of locally determined relations. With our increased precision, we find that the relation is well established by <z>~1, with no significant evolution to <z>~0.3, {Delta}M_*_~0.04+/-0.07dex. A clearer trend of evolution is seen in the B-band Tully-Fisher relation corresponding to a decline in luminosity of {Delta}M_B_~0.85+/-0.28 magnitudes at fixed velocity over the same redshift range, reflecting the changes in star formation over this period. As an illustration of the opportunities possible when gas masses are available for a sample such as ours, we show how our dynamical and stellar mass data can be used to evaluate the likely contributions of baryons and dark matter to the assembly history of spiral galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/1590
- Title:
- Deep spectroscopy of Abell 85
- Short Name:
- J/MNRAS/458/1590
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new deep spectroscopic catalogue for Abell 85, within 3.0x2.6Mpc^2^ and down to M_r_~M_r_^*^+6. Using the Visible Multi-Object Spectrograph at the Very Large Telescope and the AutoFiber 2 at the William Herschel Telescope, we obtained almost 1430 new redshifts for galaxies with m_r_<=21mag and <{mu}_e,r_><=24mag/arcsec^2^. These redshifts, together with Sloan Digital Sky Survey Data Release 6 and NASA/IPAC Extragaalctic Database spectroscopic information, result in 460 confirmed cluster members. This data set allows the study of the luminosity function (LF) of the cluster galaxies covering three orders of magnitudes in luminosities. The total and radial LFs are best modelled by a double Schechter function. The normalized LFs show that their bright (M_r_<=-21.5) and faint (M_r_>=-18.0) ends are independent of clustercentric distance and similar to the field LFs unlike the intermediate luminosity range (-21.5<=M_r_<=-18.0). Similar results are found for the LFs of the dominant types of galaxies: red, passive, virialized and early-infall members. On the contrary, the LFs of blue, star forming, non-virialized and recent-infall galaxies are well described by a single Schechter function. These populations contribute to a small fraction of the galaxy density in the innermost cluster region. However, in the outskirts of the cluster, they have similar densities to red, passive, virialized and early-infall members at the LF faint end. These results confirm a clear dependence of the colour and star formation of Abell 85 members in the cluster centric distance.
- ID:
- ivo://CDS.VizieR/J/ApJS/119/159
- Title:
- Deep survey of HI-selected galaxies
- Short Name:
- J/ApJS/119/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a 21cm neutral hydrogen survey of approximately 55{deg}^2^ out to a redshift of cz=8340km/s, we have identified 75 extragalactic HI sources. These objects comprise a well-defined sample of extragalactic sources chosen by means that are independent of optical surface brightness selection effects. In this paper we describe the Arecibo survey procedures and HI data, follow-up VLA HI observations made of several unusual sources, and Kitt Peak B-, R-, and I-band photometry for nearly all of the galaxies. We have also gathered information for some of the optically detected galaxies within the same search volume.
- ID:
- ivo://CDS.VizieR/J/ApJ/896/29
- Title:
- Deep UBVRI photometry of NGC6910 members
- Short Name:
- J/ApJ/896/29
- Date:
- 09 Nov 2021 14:21:10
- Publisher:
- CDS
- Description:
- Deep and wide-field optical photometric observations along with multiwavelength archival data sets have been employed to study the physical properties of the cluster NGC 6910. The study also examines the impact of massive stars on their environment. The age, distance, and reddening of the cluster are estimated to be ~4.5Myr, 1.72+/-0.08kpc, and E(B-V)_min_=0.95mag, respectively. The mass function slope ({Gamma}=-0.74+/-0.15) in the cluster region is found to be flatter than the Salpeter value (-1.35), indicating the presence of an excess number of massive stars. The cluster also shows mass segregation toward the central region due to their formation processes. The distribution of warm dust emission is investigated toward the central region of the cluster, showing the signature of the impact of massive stars within the cluster region. Radio continuum clumps powered by massive B-type stars (age range ~0.07-0.12Myr) are traced that are located away from the center of the stellar cluster NGC 6910 (age ~4.5Myr). Based on the values of different pressure components exerted by massive stars, the photoionized gas associated with the cluster is found to be the dominant feedback mechanism in the cluster. Overall, the massive stars in the cluster might have triggered the birth of young, massive B-type stars in the cluster. This argument is supported with evidence of the observed age gradient between the cluster and the powering sources of the radio clumps.
- ID:
- ivo://CDS.VizieR/J/A+A/324/549
- Title:
- Deep UVBRI photometry in IC 348
- Short Name:
- J/A+A/324/549
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table3 contains UBVRI-CCD photometry for the 123 observed stars in the nucleus of IC 348 open cluster. Magnitude and colours are given with their corresponding errors. Column "N" gives the number of observations. Spectral types and cross-identifications with other catalogues are given in note file. Table5 contains adopted reddening solution for the brightest members in IC 348
- ID:
- ivo://CDS.VizieR/J/MNRAS/431/1995
- Title:
- Deep uVI photometry of NGC2419
- Short Name:
- J/MNRAS/431/1995
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present accurate wide-field uVI photometry of the remote and massive Galactic globular cluster NGC 2419, aimed at searching for the u-V colour spread along the red giant branch (RGB) which is generally interpreted as the photometric signature of the presence of multiple populations in globular clusters. Focusing on the RGB stars in the magnitude range 19.8<=V<=22.0, we find that (i) the u-V, u-I and the V-I spreads about the RGB ridge line are significantly larger than that expected from observational errors, accurately quantified by means of extensive artificial stars experiments, (ii) the intrinsic colour spreads in u-V and u-I are larger than in V-I, and (iii) the stars lying to the blue of the RGB ridge line in u-V and u-I are significantly more concentrated towards the cluster centre than those lying to the red of that line. All the above observational facts can be interpreted in a scenario where a sizable fraction of cluster stars belong to a second generation heavily enriched in helium. Finally, we find that bright RGB stars (17.5<V<19.0) having [Mg/Fe]<0.0 lie preferentially on the red side of the cluster RGB, while those having [Mg/Fe]>0.0 lie preferentially on the blue side.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A91
- Title:
- Deep VI imaging in outer regions of M33
- Short Name:
- J/A+A/533/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Subaru/Suprime-Cam deep V and I imaging of seven fields in the outer regions of M33. Our aim is to search for stellar structures corresponding to extended HI clouds found in a recent 21-cm survey of the galaxy. Three fields probe a large HI complex to the southeastern (SE) side of the galaxy. An additional three fields cover the northwestern (NW) side of the galaxy along the HI warp. A final target field was chosen further north, at a projected distance of approximately 25kpc, to study part of the large stellar plume recently discovered around M33. We analyse the stellar population at R>10kpc by means of V, I colour magnitude diagrams reaching the red clump. We constrain the age and metallicity of the different stellar populations, search for density enhancements that correspond to the HI features, and investigate the radial surface distribution of the stars. We find evolved stellar populations in all fields out to 120' (~30kpc), while a diffuse population of young stars (~200Myr) is detected out to a galactocentric radius of 15kpc. The mean metallicity in the southern fields remains approximately constant at [M/H]=-0.7 beyond the edge of the optical disc, from 40' out to 80'. Along the northern fields probing the outer HI disc, we also find a metallicity of [M/H]=-0.7 between 35' and 70' from the centre, which decreases to [M/H]=-1.0 at larger angular radii out to 120'. In the northernmost field, outside the disc extent, the stellar population of the large stellar plume possibly related to a M33-M31 interaction is on average more metal-poor ([M/H]=-1.3) and older (>6Gyr). An exponential disc with a large scale-length (~7kpc) fits well the average distribution of stars detected in both the SE and NW regions from a galactocentric distance of 11kpc out to 30kpc. The stellar disc extends beyond the HI disc. The stellar distribution at large radii is disturbed and, although there is no clear correlation between the stellar substructures and the location of the HI clouds, this gives evidence of tidal interaction or accretion events.
- ID:
- ivo://CDS.VizieR/J/A+A/629/A18
- Title:
- Deep VI photometry of 15 dwarf galaxy candidates
- Short Name:
- J/A+A/629/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dwarf galaxy satellite systems are essential probes to test models of structure formation, making it necessary to establish a census of dwarf galaxies outside of our own Local Group. We present deep FORS2 VI band images from the ESO Very Large Telescope (VLT) for 15 dwarf galaxy candidates in the Centaurus group of galaxies. We confirm nine dwarfs to be members of Cen A by measuring their distances using a Bayesian approach to determine the tip of the red giant branch luminosity. We have also fit theoretical isochrones to measure their mean metallicities. The properties of the new dwarfs are similar to those in the Local Group in terms of their sizes, luminosities, and mean metallicities. Within our photometric precision, there is no evidence of a metallicity spread, but we do observe possible extended star formation in several galaxies, as evidenced by a population of asymptotic giant branch stars brighter than the red giant branch tip. The new dwarfs do not show any signs of tidal disruption. Together with the recently reported dwarf galaxies by the complementary PISCeS survey, we study the luminosity function and 3D structure of the group. By comparing the observed luminosity function to the high-resolution cosmological simulation IllustrisTNG, we find agreement within a 90% confidence interval.However, Cen A seems to be missing its brightest satellites and has an overabundance of the faintest dwarfs in comparison to its simulated analogs. In terms of the overall 3D distribution of the observed satellites, we find that the whole structure is flattened along the line-of-sight, with a root-mean-square (rms) height of 130kpc and an rms semi-major axis length of 330kpc. Future distance measurements of the remaining dwarf galaxy candidates are needed to complete the census of dwarf galaxies in the Centaurus group.
- ID:
- ivo://CDS.VizieR/J/A+A/570/A78
- Title:
- Deep VI photometry of Sgr dIrr
- Short Name:
- J/A+A/570/A78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric catalogue of the dwarf irregular galaxy Sagittarius. The catalogue is obtained from deep V and I band wide field photometry from VIMOS at VLT. Only sources having at least six independent magnitude estimates per filter were included in this catalogue. The average and the standard error of the mean of the independent measures obtained from the different images were adopted as the final values of the instrumental magnitude and of the uncertainty on the relative photometry. The instrumental v and i magnitudes were transformed into the Johnson-Kron-Cousins V,I photometric system using more than 70 bright stars (V<22.5) in common with the publicly available HST Wide Field and Planetary Camera 2 (WFPC2) photometry by Holtzman et al. (2006ApJS..166..534H). The instrumental coordinates were transformed into J2000 Equatorial coordinates with 2nd degree polynomials, using more than 1000 stars in common with the GSC2.2 catalog. Please see Section 2.2 for details.