- 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}_.
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- 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.
- ID:
- ivo://CDS.VizieR/J/MNRAS/464/194
- Title:
- Metallicity distribution in the GC
- Short Name:
- J/MNRAS/464/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Knowing the metallicity distribution of stars in the Galactic Centre has important implications for the formation history of the Milky Way nuclear star cluster. However, this distribution is not well known, and is currently based on a small sample of fewer than 100 stars. We obtained near-infrared K-band spectra of more than 700 late-type stars in the central 4pc^2^ of the Milky Way nuclear star cluster with the integral-field spectrograph KMOS (VLT). We analyse the medium-resolution spectra using a full-spectral fitting method employing the Gottingen spectral library of synthetic PHOENIX spectra. The derived stellar metallicities range from metal-rich [M/H]>+0.3dex to metal-poor [M/H]<-1.0dex, with a fraction of 5.2^+6.0^_-3.1_ per cent metal-poor ([M/H]<=-0.5dex) stars. The metal-poor stars are distributed over the entire observed field. The origin of metal-poor stars remains unclear. They could originate from infalling globular clusters. For the metal-rich stellar population ([M/H]>0dex), a globular cluster origin can be ruled out. As there is only a very low fraction of metal-poor stars in the central 4pc^2^ of the Galactic Centre, we believe that our data can discard a scenario in which the Milky Way nuclear star cluster is purely formed from infalling globular clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A80
- Title:
- Metallicity of bulge clump giants in Baade's window
- Short Name:
- J/A+A/534/A80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We seek to constrain the formation of the Galactic bulge by means of analysing the detailed chemical composition of a large sample of red clump stars in Baade's window. These stars were selected to minimise the contamination by other Galactic components, so they are good tracers of the bulge metallicity distribution in Baade's window, at least for stars more metal-rich than ~-1.5. We used an automatic procedure to measure [Fe/H] in a sample of 219 bulge red clump stars from R=20000 resolution spectra obtained with FLAMES/GIRAFFE at the VLT. The analysis was performed differentially with respect to the metal-rich local reference star MuLeo. For a subsample of 162 stars, we also derived [Mg/H] from spectral synthesis around the MgI triplet at 6319{AA}. The Fe and Mg metallicity distributions are both asymmetric with median values of +0.16 and +0.21, respectively. They show only a small proportion of stars at low metallicities, extending down to [Fe/H]=-1.1 or [Mg/H]=-0.7 The iron distribution is clearly bimodal, as revealed both by a deconvolution (from observational errors) and a Gaussian decomposition. The decomposition of the observed Fe and Mg metallicity distributions into Gaussian components yields two populations of equal sizes (50% each): a metal-poor component centred on [Fe/H]=-0.30 and [Mg/H]=-0.06 with a large dispersion and a narrow metal-rich component centred on [Fe/H]=+0.32 and [Mg/H]=+0.35. The metal-poor component shows high [Mg/Fe] ratios (around 0.3), while stars in the metal-rich component are found to have near solar ratios. Kinematical differences between the two components have also been found: the metal-poor component shows kinematics compatible with an old spheroid, while the metal-rich component is consistent with a population supporting a bar. In view of their chemical and kinematical properties, we suggest different formation scenarii for the two populations: a rapid formation time scale as an old spheroid for the metal-poor component (old bulge) and for the metal-rich component, a formation on a longer time scale driven by the evolution of the bar (pseudo-bulge).
- ID:
- ivo://CDS.VizieR/J/ApJ/798/77
- Title:
- Metallicity of RGB stars in 6 M31 dwarf galaxies
- Short Name:
- J/ApJ/798/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present global metallicity properties, metallicity distribution functions (MDFs), and radial metallicity profiles for the six most luminous M31 dwarf galaxy satellites: M32, NGC 205, NGC 185, NGC 147, Andromeda VII, and Andromeda II. The results presented are the first spectroscopic MDFs for dwarf systems surrounding a host galaxy other than the Milky Way (MW). Our sample consists of individual metallicity measurements for 1243 red giant branch member stars spread across these six systems. We determine metallicities based on the strength of the Ca II triplet lines using the empirical calibration of Carrera et al. (2013, J/MNRAS/434/1681), which is calibrated over the metallicity range -4<[Fe/H]<+0.5. We find that these M31 satellites lie on the same luminosity-metallicity relationship as the MW dwarf satellites. We do not find a trend between the internal metallicity spread and galaxy luminosity, contrary to previous studies. The MDF widths of And II and And VII are similar to the MW dwarf spheroidal (dSph) satellites of comparable luminosity; however, our four brightest M31 dwarf satellites are more luminous than any of the MW dSphs and have broader MDFs. The MDFs of our six M31 dwarf satellites are consistent with the leaky box model of chemical evolution, although our metallicity errors allow a wide range of evolution models. We find a significant radial gradient in metallicity in only two of our six systems, NGC 185 and Andromeda II, and flat radial metallicity gradients in the rest of our sample with no observed correlation between rotational support and radial metallicity gradients. Although the average properties and radial trends of the M31 dwarf galaxies agree with their MW counterparts at similar luminosity, the detailed MDFs are different, particularly at the metal-rich end.
- ID:
- ivo://CDS.VizieR/J/ApJ/808/108
- Title:
- M2FS stellar spectroscopy of Reticulum 2
- Short Name:
- J/ApJ/808/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from spectroscopic observations with the Michigan/Magellan Fiber System (M2FS) of 182 stellar targets along the line of sight (LOS) to the newly discovered "ultrafaint" object Reticulum 2 (Ret 2). For 37 of these targets, the spectra are sufficient to provide simultaneous estimates of LOS velocity ({nu}i_los_, median random error {delta}_{nu}los_=1.4km/s), effective temperature (T_eff_, {delta}_Tef_=478K), surface gravity (logg, {delta}_logg_=0.63dex), and iron abundance ([Fe/H], {delta}_[Fe/H]_=0.47dex). We use these results to confirm 17 stars as members of Ret 2. From the member sample we estimate a velocity dispersion of {sigma}_{nu}los_=3.6_-0.7_^+1.0^km/s about a mean of <{nu}_los_>=64.3_1.2_^+1.2^km/s in the solar rest frame (~-90.9km/s in the Galactic rest frame), and a metallicity dispersion of {sigma}_[Fe/H]_=0.49_-0.14_^+0.19^dex about a mean of <[Fe/H]_>=-2.58_-0.33_^+0.34^. These estimates marginalize over possible velocity and metallicity gradients, which are consistent with zero. Our results place Ret 2 on chemodynamical scaling relations followed by the Milky Way's dwarf-galactic satellites. Under assumptions of dynamic equilibrium and negligible contamination from binary stars --both of which must be checked with deeper imaging and repeat spectroscopic observations-- the estimated velocity dispersion suggests a dynamical mass of M(R_h_)~5R_h_{sigma}_{nu}los_^2^/(2G)=2.4_-0.8_^+1.4^x10^5^M_{sun}_ enclosed within projected halflight radius R_h_~32pc, with mass-to-light ratio ~2M(R_h_)/L_V_=467_-168_^+286^ in solar units.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/3811
- Title:
- M33 GALEX catalogue of UV point sources
- Short Name:
- J/MNRAS/450/3811
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The hottest stars (>10000K), and by extension typically the most massive ones, are those that will be prevalent in the ultraviolet (UV) portion of the electromagnetic spectrum, and we expect to numerous B, O and WR (WR) stars to be bright in UV data. In this paper, we update the previous point source UV catalogue of M33, created using the Ultraviolet Imaging Telescope (UIT), using data from the Galaxy Evolution Explorer (GALEX). We utilize point spread function photometry to optimally photometer sources in the crowded regions of the galaxy, and benefit from GALEX's increased sensitivity compared to UIT. We match our detections with data from the Local Group Galaxies Survey to create a catalogue with photometry spanning from the far-UV through the optical for a final list of 24738 sources. All of these sources have far-UV (FUV; 1516{AA}), near-UV (NUV; 2267{AA}) and V data, and a significant fraction also have U, B, R and I data as well. We also present an additional 3000 sources that have no matching optical counterpart. We compare all of our sources to a catalogue of known WR stars in M33 and find that we recover 114 of 206 stars with spatially-coincident UV point sources. Additionally, we highlight and investigate those sources with unique colours as well as a selection of other well-studied sources in M33.
- ID:
- ivo://CDS.VizieR/J/AJ/128/245
- Title:
- M giant stars in the Sagittarius dwarf galaxy
- Short Name:
- J/AJ/128/245
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained moderate resolution (~6km/s) spectroscopy of several hundred M giant candidates selected from Two Micron All Sky Survey photometry (Cat. <II/246>). Radial velocities are presented for stars mainly in the southern Galactic hemisphere, and the primary targets have Galactic positions consistent with association to the tidal tail system of the Sagittarius (Sgr) dwarf galaxy.
- ID:
- ivo://CDS.VizieR/J/MNRAS/455/820
- Title:
- M87 globular cluster candidates catalog
- Short Name:
- J/MNRAS/455/820
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new photometric catalogue of the rich globular cluster (GC) system around M87, the brightest cluster galaxy in Virgo. Using archival Next Generation Virgo Cluster Survey images in the ugriz bands, observed with Canada-France-Hawaii Telescope/MegaPrime, we perform a careful subtraction of the galaxy's halo light in order to detect objects at small galactocentric radii as well as in the wider field, and find 17620 GC candidates over a radius range from 1.3 to 445kpc with g<24mag. By inferring their colour, radial and magnitude distributions in a Bayesian way, we find that they are well described as a mixture of two GC populations and two distinct contaminant populations, but confirm earlier findings of radius-dependent colour gradients in both GC populations. This is consistent with a picture in which the more enriched GCs reside deeper in the galaxy's potential well, indicating a role for dissipative collapse in the formation of both the red and the blue GCs.
- ID:
- ivo://CDS.VizieR/J/AJ/119/727
- Title:
- M31 globular clusters photometry
- Short Name:
- J/AJ/119/727
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalog of photometric and spectroscopic data on M31 globular clusters (GCs). The catalog includes new optical and near-infrared photometry for a substantial fraction of the 435 clusters and cluster candidates. We use these data to determine the reddening and intrinsic colors of individual clusters, and we find that the extinction laws in the Galaxy and M31 are not significantly different. There are significant (up to 0.2 mag in V-K) offsets between the clusters' intrinsic colors and simple stellar population colors predicted by population synthesis models; we suggest that these are due to systematic errors in the models. The distributions of M31 clusters' metallicities and metallicity-sensitive colors are bimodal, with peaks at [Fe/H]~-1.4 and -0.6. The distribution of V-I is often bimodal in elliptical galaxies' globular cluster systems, but it is not sensitive enough to metallicity to show bimodality in M31 and Galactic cluster systems. The radial distribution and kinematics of the two M31 metallicity groups imply that they are analogs of the Galactic "halo" and "disk/bulge" cluster systems. The globular clusters in M31 have a small radial metallicity gradient, suggesting that some dissipation occurred during the formation of the globular cluster system. The lack of correlation between cluster luminosity and metallicity in M31 GCs shows that self-enrichment is not important in GC formation.
