- ID:
- ivo://CDS.VizieR/J/A+A/552/A12
- Title:
- Abundances of PNe in NGC 300
- Short Name:
- J/A+A/552/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained deep spectroscopy of 26 planetary nebulae (PNe) and 9 compact HII regions in the nearby spiral galaxy NGC 300, and analyzed them together with the giant HII regions observed by Bresolin et al. (2009ApJ...700..309B). We have determined the physical properties of all those objects and their content in He, N, O, Ne, S and Ar in a consistent way. We find that compact HII regions have abundances similar to those of giant HII regions, while PNe have systematically larger N/O ratios and similar Ne/O and Ar/O ratios. We demonstrate that this nitrogen enhancement in PNe cannot be due to second dredge-up in the progenitor stars, since their initial masses are around 2-2.5M_{sun}_. An extra mixing process is required, perhaps be driven by rotation. Concerning the radial abundance distribution, PNe behave differently from HII regions: In the central parts, they show an average O/H smaller by 0.15dex. Their abundance dispersion at any galactocentric radius is significantly larger than for HII regions and many of them have O/H values higher than HII regions at the same galactocentric distance, suggesting that oxygen production in the PN progenitors in NGC 300 is common. PN abundance gradients in O/H, Ne/H and Ar/He are significantly shallower than those of HII regions. We argue that this indicates a steepening of the metallicity gradient in NGC 300 during the last Gr, rather than the effect of radial stellar motions.
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- ID:
- ivo://CDS.VizieR/J/ApJ/767/134
- Title:
- Abundances of red giant stars in UFD galaxies
- Short Name:
- J/ApJ/767/134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Milky Way ultra-faint dwarf (UFD) galaxies contain some of the oldest, most metal-poor stars in the universe. We present [Mg/Fe], [Si/Fe], [Ca/Fe], [Ti/Fe], and mean [{alpha}/Fe] abundance ratios for 61 individual red giant branch stars across eight UFDs. This is the largest sample of alpha abundances published to date in galaxies with absolute magnitudes M_V_>-8, including the first measurements for Segue 1, Canes Venatici II, Ursa Major I, and Leo T. Abundances were determined via medium-resolution Keck/DEIMOS spectroscopy and spectral synthesis. The sample spans the metallicity range -3.4<[Fe/H]<-1.1. With the possible exception of Segue 1 and Ursa Major II, the individual UFDs show on average lower [{alpha}/Fe] at higher metallicities, consistent with enrichment from Type Ia supernovae. Thus, even the faintest galaxies have undergone at least a limited level of chemical self-enrichment. Together with recent photometric studies, this suggests that star formation in the UFDs was not a single burst, but instead lasted at least as much as the minimum time delay of the onset of Type Ia supernovae (~100Myr) and less than ~2Gyr. We further show that the combined population of UFDs has an [{alpha}/Fe] abundance pattern that is inconsistent with a flat, Galactic halo-like alpha abundance trend, and is also qualitatively different from that of the more luminous CVn I dSph, which does show a hint of a plateau at very low [Fe/H].
- ID:
- ivo://CDS.VizieR/J/A+A/633/A139
- Title:
- Abundances of RXC J2248.7-4431 galaxies
- Short Name:
- J/A+A/633/A139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Aims. Gas-phase metallicities offer insight into the chemical evolution of galaxies as they reflect the recycling of gas through star formation and galactic inflows and outflows. Environmental effects such as star-formation quenching mechanisms play an important role in shaping the evolution of galaxies. Clusters of galaxies at z<0.5 are expected to be the sites where environmental effects can be clearly observed with present-day telescopes. Methods. We explored the Frontier Fields cluster RX J2248-443 at z=0.348 with VIMOS/VLT spectroscopy from CLASH-VLT, which covers a central region corresponding to almost 2 virial radii. The fluxes of [OII]{lambda}3727, H{beta}, [OIII]{lambda}5007, H{alpha} and [NII]{lambda}6584 emission lines were measured allowing the derivation of (O/H) gas metallicities, star formation rates based on extinction-corrected H{alpha} fluxes, and contamination from active galactic nuclei. We compared our sample of cluster galaxies to a population of field galaxies at similar redshifts. Results. We use the location of galaxies in projected phase-space to distinguish between cluster and field galaxies. Both populations follow the star-forming sequence in the diagnostic diagrams, which allow the ionising sources in a galaxy to be disentangled, with only a low number of galaxies classified as Seyfert II. Both field and cluster galaxies follow the "main sequence" of star-forming galaxies, with no substantial difference observed between the two populations. In the mass-metallicity (MZ) plane, both high-mass field and cluster galaxies show comparable (O/H)s to the local SDSS MZ relation, with an offset of low-mass galaxies (log(M/M_{sun}_)<9.2) towards higher metallicities. While both the metallicities of "accreted" (R<R_500_) and "infalling" (R>R_500_) cluster members are comparable at all masses, the cluster galaxies from the "mass complete" bin (which is the intermediate mass bin in this study: 9.2<log(M/M_{sun}_)<10.2), show more enhanced metallicities than their field counterparts by a factor of 0.065 dex with a ~1.8{sigma} significance. The intermediate-mass field galaxies are in accordance with the expected (O/H)s from the fundamental metallicity relation, while the cluster members deviate strongly from the model predictions, namely by a factor of ~0.12dex. The results of this work are in accordance with studies of other clusters at z<0.5 and favour the scenario in which the hot halo gas of low- and intermediate-mass cluster galaxies is removed due to ram pressure stripping, leading to an increase in their gas-phase metallicity.
- ID:
- ivo://CDS.VizieR/J/ApJ/701/1053
- Title:
- Abundances of 8 stars in the Draco dSph
- Short Name:
- J/ApJ/701/1053
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an abundance analysis based on high-resolution spectra of eight stars selected to span the full range in metallicity in the Draco dwarf spheroidal (dSph) galaxy. We find that [Fe/H] for the sample stars ranges from -1.5 to -3.0dex. Combining our sample with previously published work for a total of 14 luminous Draco giants, we show that the abundance ratios [Na/Fe], [Mg/Fe], and [Si/Fe] for the Draco giants overlap those of Galactic halo giants at the lowest [Fe/H] probed, but are significantly lower for the higher Fe-metallicity Draco stars. Using a toy model we compare the behavior of the abundance ratios within the sample of Draco giants with those from the literature of Galactic globular clusters, and the Carina and Sgr dSph galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/830/93
- Title:
- Abundances of the Ret II brightest red giant members
- Short Name:
- J/ApJ/830/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present chemical abundances derived from high-resolution Magellan/Magellan Inamori Kyocera Echelle spectra of the nine brightest known red giant members of the ultra-faint dwarf galaxy Reticulum II (Ret II). These stars span the full metallicity range of Ret II (-3.5<[Fe/H]< -2). Seven of the nine stars have extremely high levels of r-process material ([Eu/Fe]~1.7), in contrast to the extremely low neutron-capture element abundances found in every other ultra-faint dwarf galaxy studied to date. The other two stars are the most metal-poor stars in the system ([Fe/H]< -3), and they have neutron-capture element abundance limits similar to those in other ultra-faint dwarf galaxies. We confirm that the relative abundances of Sr, Y, and Zr in these stars are similar to those found in r-process halo stars, but they are ~0.5dex lower than the solar r-process pattern. If the universal r-process pattern extends to those elements, the stars in Ret II display the least contaminated known r-process pattern. The abundances of lighter elements up to the iron peak are otherwise similar to abundances of stars in the halo and in other ultra-faint dwarf galaxies. However, the scatter in abundance ratios is large enough to suggest that inhomogeneous metal mixing is required to explain the chemical evolution of this galaxy. The presence of low amounts of neutron-capture elements in other ultra-faint dwarf galaxies may imply the existence of additional r-process sites besides the source of r-process elements in Ret II. Galaxies like Ret II may be the original birth sites of r-process enhanced stars now found in the halo.
- ID:
- ivo://CDS.VizieR/J/ApJ/855/83
- Title:
- Abundances of very metal-poor stars in Sagittarius
- Short Name:
- J/ApJ/855/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sagittarius (Sgr) is a massive disrupted dwarf spheroidal galaxy in the Milky Way halo that has undergone several stripping events. Previous chemical studies were restricted mainly to a few, metal-rich ([Fe/H]>~-1) stars that suggested a top-light initial mass function (IMF). Here we present the first high-resolution, very metal-poor ([Fe/H]=-1 to -3) sample of 13 giant stars in the main body of Sgr. We derive abundances of 13 elements, namely C, Ca, Co, Fe, Sr, Ba, La, Ce, Nd, Eu, Dy, Pb, and Th, that challenge the interpretation based on previous studies. Our abundances from Sgr mimic those of the metal-poor halo, and our most metal-poor star ([Fe/H]~-3) indicates a pure r-process pollution. Abundances of Sr, Pb, and Th are presented for the first time in Sgr, allowing for age determination using nuclear cosmochronology. We calculate ages of 9+/-2.5Gyr. Most of the sample stars have been enriched by a range of asymptotic giant branch (AGB) stars with masses between 1.3 and 5M_{sun}_. SgrJ190651.47-320147.23 shows a large overabundance of Pb (2.05dex) and a peculiar abundance pattern best fit by a 3M_{sun}_ AGB star. Based on star-to-star scatter and observed abundance patterns, a mixture of low- and high-mass AGB stars and supernovae (15-25M_{sun}_) is necessary to explain these patterns. The high level (0.29+/-0.05dex) of Ca indicates that massive supernovae must have existed and polluted the early ISM of Sgr before it lost its gas. This result is in contrast with a top-light IMF with no massive stars polluting Sgr.
- 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/A+A/621/A133
- Title:
- ABYSS HUDF WFC3 IR mosaics
- Short Name:
- J/A+A/621/A133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Hubble Ultra Deep field (HUDF) is the deepest region ever observed with the Hubble Space Telescope. With the main objective of unveiling the nature of galaxies up to z~7-8, the observing and reduction strategy have focused on the properties of small and unresolved objects, rather than the outskirts of the largest objects, which are usually over-subtracted. We aim to create a new set of WFC3 IR mosaics of the HUDF using novel techniques to preserve the properties of the low surface brightness regions. We created ABYSS a pipeline that optimises the estimate and modelling of low-level systematic effects to obtain a robust background subtraction. We have improved four key points in the reduction: 1) creation of new absolute sky flat fields, 2) extended persistence models, 3) dedicated sky background subtraction and 4) robust co-adding. The new mosaics successfully recover the low surface brightness structure removed on the previous HUDF published reductions. The amount of light recovered with a mean surface brightness dimmer than mu=26mag/arcsec^2^ is equivalent to a m=19 mag source when compared to the XDF and a m=20mag compared to the HUDF12. We present a set of techniques to reduce ultra-deep images (mu>32.5mag/arcsec^2^, 3 sigma in 10x10 arcsec boxes), that successfully allow to detect the low surface brightness structure of extended sources on ultra deep surveys. The developed procedures are applicable to HST, JWST, EUCLID and many other space and ground-based observatories. We made the final ABYSS WFC3 IR HUDF mosaics publicly available at http://www.iac.es/proyecto/abyss/.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A78
- Title:
- A case study of the HI content of HCG 16
- Short Name:
- J/A+A/632/A78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hickson Compact Group (HCG) 16 is a prototypical compact group of galaxies in an intermediate stage of the evolutionary sequence proposed by Verdes-Montenegro et al. (2001A&A...377..812V), where its galaxies are losing gas to the intra-group medium (IGrM). The group hosts galaxies that are HI-normal, HI-poor, centrally active with both AGN and starbursts, as well as a likely new member and a 160kpc long HI tidal feature. Despite being a well-studied group at all wavelengths, no previous study of HCG 16 has focused on its extraordinary HI component. The characteristics of HCG 16 make it an ideal case study for exploring which processes are likely to dominate the late stages of evolution in compact groups, and ultimately determine their end states. In order to build a coherent picture of the evolution of this group we make use of the multi-wavelength data available, but focus particularly on HI as a tracer of interactions and evolutionary phase. We reprocess archival VLA L-band observations of HCG 16 using the multi-scale CLEAN algorithm to accurately recover diffuse features. Tidal features and galaxies are separated in 3 dimensions using the SlicerAstro package. The HI deficiency of the separated galaxies is assessed against the benchmark of recent scaling relations of isolated galaxies. This work has been performed with particular attention to reproducibility and is accompanied by a complete workflow to reproduce all the final data products, figures, and results. Despite the clear disruption of the HI component of HCG 16 we find that it is not globally HI deficient, even though HCG 16a and b have lost the majority of their HI and almost 50% of the group's HI is in the IGrM. The HI content of HCG 16d shows highly disturbed kinematics, with only a marginal velocity gradient that is almost perpendicular to its optical major axis. The ~160kpc long tail extending towards the South-East appears to be part of an even larger structure which spatially and kinematically connects NGC 848 to the North-West corner of the group. This study indicates that in the recent past (1Gyr) galaxies HCG 16a and b likely underwent major interactions that unbound gas without triggering significant star formation. This gas was then swept away by a high speed, close encounter with NGC 848. The starburst events HCG 16c and d, likely initiated by their mutual interaction, have triggered galactic winds which, in the case of HCG 16d, appears to have disrupted its HI reservoir. The tidal features still connected to all these galaxies indicate that more HI will soon be lost to the IGrM, while that which remains in the discs will likely be consumed by star formation episodes triggered by their on-going interaction. This is expected to result in a collection of gas-poor galaxies embedded in a diffuse HI structure, which will gradually (over several Gyr) be evaporated by the UV background, resembling the final stage of the evolutionary model of compact groups.
