- ID:
- ivo://CDS.VizieR/J/ApJ/705/328
- Title:
- Abundance measurements in Sculptor dSph
- Short Name:
- J/ApJ/705/328
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of Fe, Mg, Si, Ca, and Ti abundances for 388 radial velocity member stars in the Sculptor dwarf spheroidal galaxy (dSph), a satellite of the Milky Way (MW). This is the largest sample of individual {alpha} element (Mg, Si, Ca, and Ti) abundance measurements in any single dSph. The measurements are made from Keck/Deep Imaging Multi-Object Spectrometer medium-resolution spectra (6400-9000{AA}, R~6500). Based on comparisons to published high-resolution (R>~20000) spectroscopic measurements, our measurements have uncertainties of {alpha}[Fe/H]=0.14 and {alpha}[{alpha}/Fe]=0.13. We have discovered one star with [Fe/H]=-3.80+/-0.28, which is the most metal-poor star known anywhere except the MW halo, but high-resolution spectroscopy is needed to measure this star's detailed abundances.
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- ID:
- ivo://CDS.VizieR/J/ApJS/191/352
- Title:
- Abundances in stars of Milky Way dwarf satellites
- Short Name:
- J/ApJS/191/352
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of Fe, Mg, Si, Ca, and Ti abundances for 2961 stars in eight dwarf satellite galaxies of the Milky Way (MW): Sculptor, Fornax, Leo I, Sextans, Leo II, Canes Venatici I, Ursa Minor, and Draco. For the purposes of validating our measurements, we also observed 445 red giants in MW globular clusters and 21 field red giants in the MW halo. The measurements are based on Keck/DEIMOS medium-resolution spectroscopy (MRS) combined with spectral synthesis. We estimate uncertainties in [Fe/H] by quantifying the dispersion of [Fe/H] measurements in a sample of stars in monometallic globular clusters (GCs). We estimate uncertainties in Mg, Si, Ca, and Ti abundances by comparing to high-resolution spectroscopic abundances of the same stars. For this purpose, a sample of 132 stars with published high-resolution spectroscopy in GCs, the MW halo field, and dwarf galaxies has been observed with MRS. The standard deviations of the differences in [Fe/H] and <[{alpha}/Fe]> (the average of [Mg/Fe], [Si/Fe], [Ca/Fe], and [Ti/Fe]) between the two samples is 0.15 and 0.16, respectively.
- ID:
- ivo://CDS.VizieR/J/ApJ/723/1632
- Title:
- Abundance spreads in Bootes I and Segue 1
- Short Name:
- J/ApJ/723/1632
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an AAOmega spectroscopic study of red giants in the ultra-faint dwarf galaxy Bootes I (M_V_~-6) and the Segue 1 system (M_V_~-1.5), either an extremely low luminosity dwarf galaxy or an unusually extended globular cluster. Both Bootes I and Segue 1 have significant abundance dispersions in iron and carbon. Bootes I has a mean abundance of [Fe/H]=-2.55+/-0.11 with an [Fe/H] dispersion of {sigma}=0.37+/-0.08, and abundance spreads of {Delta}[Fe/H]=1.7 and {Delta}[C/H]=1.5. Segue 1 has a mean of [Fe/H]=-2.7+/-0.4 with [Fe/H] dispersion of {sigma}=0.7+/-0.3, and abundances spreads of {Delta}[Fe/H]=1.6 and {Delta}[C/H]=1.2. Moreover, Segue 1 has a radial-velocity member at four half-light radii that is extremely metal-poor and carbon-rich, with [Fe/H]=-3.5, and [C/Fe]=+2.3. Modulo an unlikely non-member contamination, the [Fe/H] abundance dispersion confirms Segue 1 as the least-luminous ultra-faint dwarf galaxy known.
- ID:
- ivo://CDS.VizieR/J/A+A/538/A100
- Title:
- Abundances red giants in Carina dSph
- Short Name:
- J/A+A/538/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ages of individual Red Giant Branch stars can range from 1Gyr old to the age of the Universe, and it is believed that the abundances of most chemical elements in their photospheres remain unchanged with time (those that are not affected by the first dredge-up). This means that they trace the interstellar medium in the galaxy at the time the star formed, and hence the chemical enrichment history of the galaxy. Colour-Magnitude Diagram analysis has shown the Carina dwarf spheroidal to have had an unusually episodic star formation history and this is expected to be reflected in the abundances of different chemical elements.
- ID:
- ivo://CDS.VizieR/J/MNRAS/385/1270
- Title:
- Age-metallicity relation via photometry
- Short Name:
- J/MNRAS/385/1270
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a widely used stellar-population synthesis model, we study the possibility of using pairs of AB system colours to break the well-known stellar age-metallicity degeneracy and to give constraints on two luminosity-weighted stellar-population parameters (age and metallicity). We present the relative age and metallicity sensitivities of the AB system colours that relate to the u, B, g, V, r, R, i, I, z, J,H and K bands, and we quantify the ability of various colour pairs to break the age-metallicity degeneracy. The results also show that the stellar ages and metallicities of galaxies observed by the Sloan Digital Sky Survey and the Two-Micron All-Sky Survey can be estimated via photometry data.
- ID:
- ivo://CDS.VizieR/J/ApJ/725/200
- Title:
- An updated catalog of M31 globular-like clusters
- Short Name:
- J/ApJ/725/200
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an updated UBVRI photometric catalog containing 970 objects in the field of M31, selected from the Revised Bologna Catalog (RBC v.4.0), including 965, 967, 965, 953, and 827 sources in the individual UBVRI bands, respectively, of which 205, 123, 14, 126, and 109 objects do not have previously published photometry. Photometry is performed using archival images from the Local Group Galaxies Survey, which covers 2.2deg^2^ along the major axis of M31. Detailed comparisons show that our photometry is fully consistent with previous measurements in all filters. We focus on 445 confirmed "globular-like" clusters and candidates, comprising typical globular and young massive clusters. The ages and masses of these objects are derived by comparing their observed spectral-energy distributions with simple stellar population synthesis. Approximately half of the clusters are younger than 2Gyr, suggesting that there has been significant recent active star formation in M31, which is consistent with previous results.
- ID:
- ivo://CDS.VizieR/J/ApJ/715/506
- Title:
- Aromatic inventory of the local volume
- Short Name:
- J/ApJ/715/506
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using infrared photometry from the Spitzer Space Telescope, we perform the first inventory of aromatic feature emission (also commonly referred to as polycyclic aromatic hydrocarbon emission) for a statistically complete sample of star-forming galaxies in the local volume. The photometric methodology involved is calibrated and demonstrated to recover the aromatic fraction of the Infrared Array Camera 8um flux with a standard deviation of 6% for a training set of 40 SINGS galaxies (ranging from stellar to dust dominated; Kennicutt et al. 2003PASP..115..928K) with both suitable mid-infrared Spitzer Infrared Spectrograph spectra and equivalent photometry. A potential factor of 2 improvement could be realized with suitable 5.5um and 10um photometry, such as what may be provided in the future by the James Webb Space Telescope. The resulting technique is then applied to mid-infrared photometry for the 258 galaxies from the Local Volume Legacy (LVL; Dale et al. 2009, Cat. J/ApJ/703/517) survey, a large sample dominated in number by low-luminosity dwarf galaxies for which obtaining comparable mid-infrared spectroscopy is not feasible. Using oxygen abundances compiled from the literature for 129 of the 258 LVL galaxies, we find a correlation between metallicity and the aromatic-to-total infrared emission ratio but not the aromatic-to-total 8um dust emission ratio. A possible explanation is that metallicity plays a role in the abundance of aromatic molecules relative to the total dust content, but other factors, such as star formation and/or the local radiation field, affect the excitation of those molecules.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A122
- Title:
- Cetus dSph stellar chemo-kinematics
- Short Name:
- J/A+A/618/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cetus is an isolated, dwarf spheroidal (dSph) galaxy at a distance of 755kpc. In order to quantify its stellar chemo-kinematical properties, we observed individual red giants branch stars in Cetus with the Very Large Telescope (VLT) FORS2 instrument, in Mask eXchange Unit (MXU) configuration. The kinematic analysis shows that Cetus is a mainly pressure-supported ({sigma}_v_=11.0^+1.6^_-1.3_km/s), dark-matter-dominated system (M_1/2_/L_V_=23.9^+9.7^_-8.9_M_{sun}_/L_{sun}_) with no significant signs of internal rotation. We find Cetus to be a metal-poor system with a significant metallicity spread (median [Fe/H]=-1.71dex, median-absolute-deviation =0.49dex), as expected for its stellar mass. We report the presence of a mild metallicity gradient compatible with those found in other dSphs of the same luminosity; we trace the presence of a stellar population gradient also in the spatial distribution of stars in different evolutionary phases in ancillary photometric data. There are tentative indications of two chemo-kinematically distinct sub-populations, with the more metal-poor stars showing a hotter kinematics than the metal-richer ones. Our results add Cetus to the growing scatter in stellar-dark matter halo properties in low-mass galactic systems. The presence of a metallicity gradient akin to those found in similar systems inhabiting different environments may hint at metallicity gradients in Local Group early-type dwarfs being driven by internal mechanisms.
- ID:
- ivo://CDS.VizieR/J/ApJS/237/18
- Title:
- Cr, Co, and Ni abundances for metal-poor red giants
- Short Name:
- J/ApJS/237/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the abundances of chromium, cobalt, and nickel in 4113 red giants, including 2277 stars in globular clusters (GCs), 1820 stars in the Milky Way's dwarf satellite galaxies, and 16 field stars. We measured the abundances from mostly archival Keck/DEIMOS medium-resolution spectroscopy with a resolving power of R~6500 and a wavelength range of approximately 6500-9000{AA}. The abundances were determined by fitting spectral regions that contain absorption lines of the elements under consideration. We used estimates of temperature, surface gravity, and metallicity that we previously determined from the same spectra. We estimated systematic error by examining the dispersion of abundances within mono- metallic GCs. The median uncertainties for [Cr/Fe], [Co/Fe], and [Ni/Fe] are 0.20, 0.20, and 0.13, respectively. Finally, we validated our estimations of uncertainty through duplicate measurements, and we evaluated the accuracy and precision of our measurements through comparison to high-resolution spectroscopic measurements of the same stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/599/1006
- Title:
- DEEP Groth Strip Survey. VII.
- Short Name:
- J/ApJ/599/1006
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using spectroscopic data from the Deep Extragalactic Evolutionary Probe Groth Strip Survey (DGSS), we analyze the gas-phase oxygen abundances in the warm ionized medium for 64 emission-line field galaxies in the redshift range 0.26<z<0.82. These galaxies comprise a small subset selected from among 693 objects in the DGSS. They are chosen for chemical analysis by virtue of having the strongest emission lines. Oxygen abundances relative to hydrogen are in the range 8.4<12+log(O/H)<9.0 with typical internal plus systematic measurement uncertainties of 0.17dex. The 64 DGSS galaxies collectively exhibit an increase in metallicity with B-band luminosity, i.e., an L-Z relation like that seen among local galaxies. Using the DGSS sample and local galaxy samples for comparison, we searched for a "second parameter" that might explain some of the dispersion seen in the L-Z relation. Parameters such as galaxy color, emission-line equivalent width, and effective radius were explored but found to be uncorrelated with residuals from the mean L-Z relation.
