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- ID:
- ivo://CDS.VizieR/J/ApJ/819/73
- Title:
- Metallicity evolution of COSMOS BCD sample
- Short Name:
- J/ApJ/819/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present oxygen abundance measurements for 74 blue compact dwarf (BCD) galaxies in the redshift range of [0.2, 0.5] using the strong-line method. The spectra of these objects are taken using Hectospec on the Multiple Mirror Telescope. More than half of these BCDs had dust attenuation corrected using the Balmer decrement method. For comparison, we also selected a sample of 2023 local BCDs from the Sloan Digital Sky Survey (SDSS) database. Based on the local and intermediate-z BCD samples, we investigated the cosmic evolution of the metallicity, star formation rate (SFR), and D_n_(4000) index. Compared with local BCDs, the intermediate-z BCDs had a systematically higher R23 ratio but a similar O32 ratio. Interestingly, no significant deviation in the mass-metallicity (MZ) relation was found between the intermediate-z and local BCDs. Besides the metallicity, the intermediate-z BCDs also exhibited an SFR distribution that was consistent with local BCDs, suggesting a weak dependence on redshift. The intermediate-z BCDs seemed to be younger than the local BCDs with lower D_n_(4000) index values. The insignificant deviation in the mass-metallicity and mass-SFR relations between intermediate-z and local BCDs indicates that the relations between the global parameters of low-mass compact galaxies may be universal. These results from low-mass compact galaxies could be used to place important observational constraints on galaxy formation and evolution models.
- ID:
- ivo://CDS.VizieR/J/A+A/587/L7
- Title:
- Metallicity from Type II SN from (i)PTF
- Short Name:
- J/A+A/587/L7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Type IIP supernovae (SNe IIP) have recently been proposed as metallicity (Z) probes. The spectral models of Dessart et al. (2014MNRAS.440.1856D) showed that the pseudo-equivalent width of FeII {lambda}5018 (pEW_5018_) during the plateau phase depends on the primordial Z, but there was a paucity of SNe IIP exhibiting pEW_5018_ that were compatible with Z<0.4Z_{sun}_. This lack might be due to some physical property of the SN II population or to the fact that those SNe have been discovered in luminous, metal-rich targeted galaxies. Here we use SN II observations from the untargeted (intermediate) Palomar Transient Factory [(i)PTF] survey, aiming to investigate the pEW_5018_ distribution of this SN population and, in particular, to look for the presence of SNe II at lower Z. We perform pEW_5018_ measurements on the spectra of a sample of 39 (i)PTF SNe II, selected to have well-constrained explosion epochs and light-curve properties. Based on the comparison with the pEW_5018_ spectral models, we subgrouped our SNe into four Z bins from Z=~0.1 Z_{sun}_ up to Z=~2 Z_{sun}_. We also independently investigated the Z of the hosts by using their absolute magnitudes and colors and, in a few cases, using strong-line diagnostics from spectra. We searched for possible correlations between SN observables, such as their peak magnitudes and the Z inferred from pEW_5018_. We found 11 events with pEW_5018_ that were small enough to indicate Z=~0.1 Z_{sun}_. The trend of pEW_5018_ with Z matches the Z estimates obtained from the host-galaxy photometry, although the significance of the correlation is weak. We also found that SNe with brighter peak magnitudes have smaller pEW_5018_ and occur at lower Z.
- ID:
- ivo://CDS.VizieR/J/ApJ/862/110
- Title:
- Metallicity measurements in 70 nearby galaxies
- Short Name:
- J/ApJ/862/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the metallicity dependence of HI surface densities in star-forming regions along many lines of sight within 70 nearby galaxies, probing kiloparsec to 50pc scales. We employ HI, SFR, stellar mass, and metallicity (gradient) measurements from the literature, spanning a wide range (5dex) in stellar and gas mass and (1.6dex) in metallicity. We consider metallicities as observed, or rescaled to match the mass-metallicity relation determined for SDSS galaxies. At intermediate to high metallicities (0.3-2 times solar), we find that the HI surface densities saturate at sufficiently large total gas surface density. The maximal HI columns vary approximately inversely with metallicity, and show little variation with spatial resolution, galactocentric radius, or among galaxies. In the central parts of massive spiral galaxies, the HI gas is depressed by factors of ~2. The observed behavior is naturally reproduced by metallicity dependent shielding theories for the HI-to-H2 transitions in star-forming galaxies. We show that the inverse scaling of the maximal HI columns with metallicity suggests that the area filling fraction of atomic-molecular complexes in galaxies is of the order of unity, and weakly dependent on metallicity.
- ID:
- ivo://CDS.VizieR/J/ApJ/775/125
- Title:
- Metallicity of galaxies from colors
- Short Name:
- J/ApJ/775/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- There is a well known correlation between the mass and metallicity of star-forming galaxies. Because mass is correlated with luminosity, this relation is often exploited, when spectroscopy is not available, to estimate galaxy metallicities based on single band photometry. However, we show that galaxy color is typically more effective than luminosity as a predictor of metallicity. This is a consequence of the correlation between color and the galaxy mass-to-light ratio and the recently discovered correlation between star formation rate (SFR) and residuals from the mass-metallicity relation. Using Sloan Digital Sky Survey spectroscopy of ~180000 nearby galaxies, we derive "LZC relations," empirical relations between metallicity (in seven common strong line diagnostics), luminosity, and color (in 10 filter pairs and four methods of photometry). We show that these relations allow photometric metallicity estimates, based on luminosity and a single optical color, that are ~50% more precise than those made based on luminosity alone; galaxy metallicity can be estimated to within ~0.05-0.1 dex of the spectroscopically derived value depending on the diagnostic used. Including color information in photometric metallicity estimates also reduces systematic biases for populations skewed toward high or low SFR environments, as we illustrate using the host galaxy of the supernova SN 2010ay. This new tool will lend more statistical power to studies of galaxy populations, such as supernova and gamma-ray burst host environments, in ongoing and future wide-field imaging surveys.
- ID:
- ivo://CDS.VizieR/J/ApJ/834/186
- Title:
- Metallicity of MPA-JHU SDSS-DR7 dwarf galaxies
- Short Name:
- J/ApJ/834/186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study how the cosmic environment affects galaxy evolution in the universe by comparing the metallicities of dwarf galaxies in voids with dwarf galaxies in more dense regions. Ratios of the fluxes of emission lines, particularly those of the forbidden [OIII] and [SII] transitions, provide estimates of a region's electron temperature and number density. From these two quantities and the emission line fluxes [OII]{lambda}3727, [OIII]{lambda}4363, and [OIII]{lambda}{lambda}4959,5007, we estimate the abundance of oxygen with the direct T_e_ method. We estimate the metallicity of 42 blue, star-forming void dwarf galaxies and 89 blue, star-forming dwarf galaxies in more dense regions using spectroscopic observations from the Sloan Digital Sky Survey Data Release 7, as reprocessed in the MPA-JHU value-added catalog. We find very little difference between the two sets of galaxies, indicating little influence from the large-scale environment on their chemical evolution. Of particular interest are a number of extremely metal-poor dwarf galaxies that are less prevalent in voids than in the denser regions.
- 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/758/133
- Title:
- Metallicity profile of M31 HII regions and PNe
- Short Name:
- J/ApJ/758/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The oxygen abundance gradients among nebular emission line regions in spiral galaxies have been used as important constraints for models of chemical evolution. We present the largest-ever full-wavelength optical spectroscopic sample of emission line nebulae in a spiral galaxy (M31). We have collected spectra of 253 HII regions and 407 planetary nebulae (PNe) with the Hectospec multi-fiber spectrograph of the MMT. We measure the line-of-sight extinction for 199 HII regions and 333 PNe; we derive oxygen abundance directly, based on the electron temperature, for 51 PNe; and we use strong-line methods to estimate oxygen abundance for 192 HII regions and nitrogen abundance for 52 HII regions. The relatively shallow oxygen abundance gradient of the more extended HII regions in our sample is generally in agreement with the result of Zaritsky et al. (1994ApJ...420...87Z), based on only 19 M31 HII regions, but varies with the strong-line diagnostic employed. Our large sample size demonstrates that there is significant intrinsic scatter around this abundance gradient, as much as ~3 times the systematic uncertainty in the strong-line diagnostics. The intrinsic scatter is similar in the nitrogen abundances, although the gradient is significantly steeper. On small scales (deprojected distance <0.5kpc), HII regions exhibit local variations in oxygen abundance that are larger than 0.3dex in 33% of neighboring pairs. We do not identify a significant oxygen abundance gradient among PNe, but we do find a significant gradient in the [NII] ratio that varies systematically with surface brightness. Our results underscore the complex and inhomogeneous nature of the interstellar medium of M31, and our data set illustrates systematic effects relevant to future studies of the metallicity gradients in nearby spiral galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/711/350
- Title:
- Metal-poor giant Boo-1137 abundances
- Short Name:
- J/ApJ/711/350
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-resolution (R~40000), high-signal-to-noise ratio (20-90) spectra of an extremely metal-poor giant star Boo-1137 in the "ultra-faint" dwarf spheroidal galaxy (dSph) Bootes I, absolute magnitude M_V_~-6.3. We derive an iron abundance of [Fe/H]=-3.7, making this the most metal-poor star as yet identified in an ultra-faint dSph. Our derived effective temperature and gravity are consistent with its identification as a red giant in Bootes I. Abundances for a further 15 elements have also been determined. Comparison of the relative abundances, [X/Fe], with those of the extremely metal-poor red giants of the Galactic halo shows that Boo-1137 is "normal" with respect to C and N, the odd-Z elements Na and Al, the iron-peak elements, and the neutron-capture elements Sr and Ba, in comparison with the bulk of the Milky Way halo population having [Fe/H]<~-3.0. The {alpha}-elements Mg, Si, Ca, and Ti are all higher by {Delta}[X/Fe]~0.2 than the average halo values. Monte Carlo analysis indicates that {Delta}[{alpha}/Fe] values this large are expected with a probability ~0.02. The elemental abundance pattern in Boo-1137 suggests inhomogeneous chemical evolution, consistent with the wide internal spread in iron abundances we previously reported.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/4326
- Title:
- Metal-rich damped Ly{alpha} systems at z~2
- Short Name:
- J/MNRAS/452/4326
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using our sample of the most metal-rich damped Lyman {alpha} systems (DLAs) at z_abs_~2, and two literature compilations of chemical abundances in 341 DLAs and 2818 stars, we present an analysis of the chemical composition of DLAs in the context of the Local Group. The metal-rich sample of DLAs at z_abs~2 probes metallicities as high as the Galactic disc and the most metal-rich dwarf spheroidals (dSphs), permitting an analysis of many elements typically observed in DLAs (Fe, Zn, Cr, Mn, Si, and S) in comparison to stellar abundances observed in the Galaxy and its satellites (in particular dSphs). Our main conclusions are: (1) non-solar [Zn/Fe] abundances in metal-poor Galactic stars and in dSphs over the full metallicity range probed by DLAs, suggest that Zn is not a simple proxy for Fe in DLAs and therefore not a suitable indicator of dust depletion. After correcting for dust depletion, the majority of DLAs have subsolar [Zn/Fe] similar to dSphs; (2) at [Fe/H]~-0.5, a constant [Mn/Fe]~-0.5 and near-solar [{alpha}/Fe] (requiring an assumption about dust depletion) are in better agreement with dwarf galaxies than Galactic disc stars; (3) [{alpha}/Zn] is usually solar or subsolar in DLAs. However, although low ratios of [{alpha}/Fe] are usually considered more 'dwarf-like' than `Milky Way-like', subsolar [Zn/Fe] in Local Group dwarfs leads to supersolar [{alpha}/Zn] in the dSphs, in contrast with the DLAs. Therefore, whilst DLAs exhibit some similarities with the Local Group dwarf population, there are also notable differences.