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3921. Merging galaxy cluster A2255 in mid-IR
ID:
ivo://CDS.VizieR/J/ApJ/727/14
Title:
Merging galaxy cluster A2255 in mid-IR
Short Name:
J/ApJ/727/14
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the mid-infrared (MIR) observation of a nearby galaxy cluster, A2255, by the AKARI space telescope. Using AKARI's continuous wavelength coverage between 3 and 24um and the wide field of view, we investigate the properties of cluster member galaxies to see how the infall of the galaxies, the cluster substructures, and the cluster-cluster merger influence their evolution. We show that the excess of MIR (~11um) flux is a good indicator for discriminating galaxies at different evolutionary stages and for dividing galaxies into three classes accordingly: strong MIR-excess (N3-S11>0.2) galaxies that include both unobscured and obscured star-forming galaxies; weak MIR-excess (-2.0<N3-S11<-1.2) galaxies that are quiescent, old (>5Gyr) galaxies where the MIR emission arises mainly from the circumstellar dust around AGB stars; and intermediate MIR-excess (-1.2<N3-S11<0.2) galaxies in between the two classes that are less than a few Gyr old past the prime star formation activity. With the MIR-excess diagnostics, we investigate how local and cluster-scale environments affect the individual galaxies. We derive the total star formation rate (SFR) and the specific SFR of A2255 using the strong MIR-excess galaxies.
3922. Merging galaxy cluster deep observations
ID:
ivo://CDS.VizieR/J/ApJS/240/39
Title:
Merging galaxy cluster deep observations
Short Name:
J/ApJS/240/39
Date:
18 Jan 2022 14:59:05
Publisher:
CDS
Description:
Multi-band photometric and multi-object spectroscopic surveys of merging galaxy clusters allow for the characterization of the distributions of constituent DM and galaxy populations, constraints on the dynamics of the merging subclusters, and an understanding of galaxy evolution of member galaxies. We present deep photometric observations from Subaru/SuprimeCam and a catalog of 4431 spectroscopic galaxies from Keck/DEIMOS observations of 29 merging galaxy clusters ranging in redshift from z=0.07 to 0.55. The ensemble is compiled based on the presence of radio relics, which highlight cluster-scale collisionless shocks in the intracluster medium. Together with the spectroscopic and photometric information, the velocities, timescales, and geometries of the respective merging events may be tightly constrained. In this preliminary analysis, the velocity distributions of 28 of the 29 clusters are shown to be well fit by single Gaussians. This indicates that radio-relic mergers largely occur transverse to the line of sight and/or near-apocenter. In this paper, we present our optical and spectroscopic surveys, preliminary results, and a discussion of the value of radio-relic mergers for developing accurate dynamical models of each system.
3923. MESS: Multi-wavelength Extreme Starburst Sample
ID:
ivo://CDS.VizieR/J/AJ/140/2052
Title:
MESS: Multi-wavelength Extreme Starburst Sample
Short Name:
J/AJ/140/2052
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper introduces the Multi-wavelength Extreme Starburst Sample (MESS), a new catalog of 138 star-forming galaxies (0.1<z<0.3) optically selected from the Sloan Digital Sky Survey using emission line strength diagnostics to have a high absolute star formation rate (SFR; minimum 11M_{sun}_/yr with median SFR~61M_{sun}_/yr based on a Kroupa initial mass function). The MESS was designed to complement samples of nearby star-forming galaxies such as the luminous infrared galaxies (LIRGs) and ultraviolet luminous galaxies (UVLGs). Observations using the Multi-band Imaging Photometer (24, 70, and 160um channels) on the Spitzer Space Telescope indicate that the MESS galaxies have IR luminosities similar to those of LIRGs, with an estimated median total IR luminosity L_IR_=~3x10^11^L_{sun}_.
3924. Metallicities & activities of southern stars
ID:
ivo://CDS.VizieR/J/A+A/485/571
Title:
Metallicities & activities of southern stars
Short Name:
J/A+A/485/571
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results from high-resolution spectroscopic measurements to determine metallicities and activities of bright stars in the southern hemisphere.
3925. Metallicities and ages in Leo II dSph
ID:
ivo://CDS.VizieR/J/AJ/133/270
Title:
Metallicities and ages in Leo II dSph
Short Name:
J/AJ/133/270
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present metallicities and ages for 52 red giants in the remote Galactic dwarf spheroidal (dSph) galaxy Leo II. These stars cover the entire surface area of Leo II and are radial velocity members. We obtained medium-resolution multifiber spectroscopy with FLAMES as part of a Large Program with the Very Large Telescope at the European Southern Observatory, Chile. The metallicities were determined based on the well-established near-infrared Ca II triplet technique.
3926. Metallicities in the Geneva photometric system
ID:
ivo://CDS.VizieR/J/MNRAS/469/3042
Title:
Metallicities in the Geneva photometric system
Short Name:
J/MNRAS/469/3042
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use the most homogeneous Geneva seven-colour photometric system to derive new metallicity calibrations for early A- to K-type stars that cover both, dwarf stars and giants. The calibrations are based on several spectroscopic data sets that were merged to a common scale, and we applied them to open cluster data to obtain an additional proof of the metallicity scale and accuracy. In total, metallicities of 54 open clusters are presented. The accuracy of the calibrations for single stars is in general below 0.1dex, but for the open cluster sample with mean values based on several stars we find a much better precision, a scatter as low as about 0.03dex. Furthermore, we combine the new results with another comprehensive photometric data set to present a catalogue of mean metallicities for more than 3000 F- and G-type dwarf stars with sigma about 0.06dex. The list was extended by more than 1200 hotter stars up to about 8500K (or spectral type A3) by taking advantage of their almost reddening free characteristic in the new Geneva metallicity calibrations. These two large samples are well suited as primary or secondary calibrators of other data, and we already identified about 20 spectroscopic data sets that show offsets up to about 0.4dex.
3927. Metallicities of damped Ly{alpha} systems
ID:
ivo://CDS.VizieR/J/ApJ/755/89
Title:
Metallicities of damped Ly{alpha} systems
Short Name:
J/ApJ/755/89
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present chemical abundance measurements for 47 damped Ly{alpha} (DLA) systems, 30 at z>4, observed with the Echellette Spectrograph and Imager and the High Resolution Echelle Spectrometer on the Keck telescopes. H I column densities of the DLAs are measured with Voigt profile fits to the Ly{alpha} profiles, and we find an increased number of false DLA identifications with Sloan Digital Sky Survey at z>4 due to the increased density of the Ly{alpha} forest. Ionic column densities are determined using the apparent optical depth method, and we combine our new metallicity measurements with 195 from previous surveys to determine the evolution of the cosmic metallicity of neutral gas. We find the metallicity of DLAs decreases with increasing redshift, improving the significance of the trend and extending it to higher redshifts, with a linear fit of -0.22+/-0.03 dex per unit redshift from z=0.09-5.06. The metallicity "floor" of {approx}1/600 solar continues out to z~5, despite our sensitivity for finding DLAs with much lower metallicities. However, this floor is not statistically different from a steep tail to the distribution. We also find that the intrinsic scatter of metallicity among DLAs of ~0.5dex continues out to z~5. In addition, the metallicity distribution and the {alpha}/Fe ratios of z>2 DLAs are consistent with being drawn from the same parent population with those of halo stars. It is therefore possible that the halo stars in the Milky Way formed out of gas that commonly exhibits DLA absorption at z>2.
3928. Metallicities of Pristine stars
ID:
ivo://CDS.VizieR/J/MNRAS/472/2963
Title:
Metallicities of Pristine stars
Short Name:
J/MNRAS/472/2963
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Pristine survey is a narrow-band, photometric survey focused around the wavelength region of the CaII H&K absorption lines, designed to efficiently search for extremely metal-poor stars. In this work, we use the first results of a medium-resolution spectroscopic follow-up to refine the selection criteria for finding extremely metal-poor stars ([Fe/H]<=-3.0) in the Pristine survey. We consider methods by which stars can be selected from available broad-band and infrared photometry plus the additional Pristine narrow-band photometry. The sample consists of 205 stars in the magnitude range 14<V<18. Applying the photometric selection criteria cuts the sample down to 149 stars, and from these we report a success rate of 70 per cent for finding stars with [Fe/H]<=-2.5 and 22 per cent for finding stars with [Fe/H]<=-3.0. These statistics compare favourably with other surveys that search for extremely metal-poor stars, namely an improvement by a factor of ~4-5 for recovering stars with [Fe/H]<=-3.0. In addition, Pristine covers a fainter magnitude range than its predecessors and can thus probe deeper into the Galactic halo.
3929. Metallicity calibrations for UBV photometry
ID:
ivo://CDS.VizieR/J/MNRAS/371/1793
Title:
Metallicity calibrations for UBV photometry
Short Name:
J/MNRAS/371/1793
Date:
21 Oct 2021
Publisher:
CDS
Description:
Calibrations are presented here for metallicity ([Fe/H]) in terms of the ultraviolet excess, [{Delta}(U-B) at B-V=0.6, hereafter D0.6], and also for the absolute visual magnitude (M_V_) and its difference with respect to the Hyades ({Delta}M^H^_V_) in terms of D0.6 and (B-V), making use of high-resolution spectroscopic abundances from the literature and Hipparcos parallaxes.
3930. Metallicity distribution in GC
ID:
ivo://CDS.VizieR/J/MNRAS/494/396
Title:
Metallicity distribution in GC
Short Name:
J/MNRAS/494/396
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present stellar metallicity measurements of more than 600 late-type stars in the central 10pc of the Galactic Centre. Together with our previously published KMOS data, this data set allows us to investigate, for the first time, spatial variations of the nuclear star cluster's metallicity distribution. Using the integral-field spectrograph KMOS (VLT), we observed almost half of the area enclosed by the nuclear star cluster's effective radius. We extract spectra at medium spectral resolution and apply full spectral fitting utilizing the PHOENIX library of synthetic stellar spectra. The stellar metallicities range from [M/H]=-1.25dex to [M/H]>+0.3dex, with most of the stars having supersolar metallicity. We are able to measure an anisotropy of the stellar metallicity distribution. In the Galactic north, the portion of subsolar metallicity stars with [M/H]<0.0dex is more than twice as high as in the Galactic south. One possible explanation for different fractions of subsolar metallicity stars in different parts of the cluster is a recent merger event. We propose to test this hypothesis with high- resolution spectroscopy and by combining the metallicity information with kinematic data.