APOGEE Chemical Abundances of the Sagittarius Dwarf Galaxy

AbstractObservations of stellar streams in M31’s outer halo suggest that M31 is actively accreting several dwarf galaxies and their globular clusters (GCs). Detailed abundances can chemically link clusters to their birth environments, establishing whether or not a GC has been accreted from a satellite dwarf galaxy. This talk presents the detailed chemical abundances of seven M31 outer halo GCs (with projected distances from M31 greater than 30 kpc), as derived from high-resolution integrated-light spectra taken with the Hobby Eberly Telescope. Five of these clusters were recently discovered in the Pan-Andromeda Archaeological Survey (PAndAS)—this talk presents the first determinations of integrated Fe, Na, Mg, Ca, Ti, Ni, Ba, and Eu abundances for these clusters. Four of the target clusters (PA06, PA53, PA54, and PA56) are metal-poor ([Fe/H] < -1.5), α-enhanced (though they are possibly less alpha-enhanced than Milky Way stars at the 1 sigma level), and show signs of star-to-star Na and Mg variations. The other three GCs (H10, H23, and PA17) are more metal-rich, with metallicities ranging from [Fe/H] = -1.4 to -0.9. While H23 is chemically similar to Milky Way field stars, Milky Way GCs, and other M31 clusters, H10 and PA17 have moderately-low [Ca/Fe], compared to Milky Way field stars and clusters. Additionally, PA17’s high [Mg/Ca] and [Ba/Eu] ratios are distinct from Milky Way stars, and are in better agreement with the stars and clusters in the Large Magellanic Cloud (LMC). None of the clusters studied here can be conclusively linked to any of the identified streams from PAndAS; however, based on their locations, kinematics, metallicities, and detailed abundances, the most metal-rich PAndAS clusters H23 and PA17 may be associated with the progenitor of the Giant Stellar Stream, H10 may be associated with the SW Cloud, and PA53 and PA56 may be associated with the Eastern Cloud.

Download Full-text

DUST AND CHEMICAL ABUNDANCES OF THE SAGITTARIUS DWARF GALAXY PLANETARY NEBULA Hen2-436

The Astrophysical Journal ◽

10.1088/0004-637x/729/1/39 ◽

2011 ◽

Vol 729 (1) ◽

pp. 39 ◽

Cited By ~ 30

Author(s):

Masaaki Otsuka ◽

Margaret Meixner ◽

David Riebel ◽

Siek Hyung ◽

Akito Tajitsu ◽

...

Keyword(s):

Planetary Nebula ◽

Dwarf Galaxy ◽

Chemical Abundances

Download Full-text

Haro15: Is it actually a low metallicity galaxy?

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310000657 ◽

2009 ◽

Vol 5 (S265) ◽

pp. 243-244

Author(s):

Verónica Firpo ◽

Guillermo Bosch ◽

Guillermo Hägele ◽

Ángeles I. Díaz ◽

Nidia Morrell

Keyword(s):

Dwarf Galaxy ◽

Empirical Methods ◽

Chemical Abundances ◽

Physical Conditions ◽

Ionization Structure ◽

The Galaxy ◽

Low Metallicity ◽

Echelle Spectroscopy ◽

Abundance Determination ◽

Blue Compact Dwarf Galaxy

AbstractWe present a detailed study of the physical properties of the nebular material in multiple knots of the blue compact dwarf galaxy Haro 15. Using long slit and echelle spectroscopy, obtained at Las Campanas Observatory, we study the physical conditions (electron density and temperature), ionic and total chemical abundances of several atoms, reddening and ionization structure. The latter was derived by comparing the oxygen and sulphur ionic ratios to their corresponding observed emission line ratios (the η and η' plots) in different regions of the galaxy. Applying direct and empirical methods for abundance determination, we perform a comparative analysis between these regions.

Download Full-text

Pair lines of sight observations of multiphase gas bearing O vi in a galaxy environment

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab396 ◽

2021 ◽

Vol 503 (3) ◽

pp. 3243-3261

Author(s):

Pratyush Anshul ◽

Anand Narayanan ◽

Sowgat Muzahid ◽

Alexander Beckett ◽

Simon L Morris

Keyword(s):

Column Density ◽

Dwarf Galaxy ◽

Formation Rate ◽

Angular Separation ◽

The Other ◽

Chemical Abundances ◽

Lower Column ◽

Solar Metallicity ◽

Galaxy Environment ◽

Collisional Ionization

ABSTRACT Using HST/COS spectra of the twin quasar lines of sight Q 0107–025A & Q 0107–025B, we report on the physical properties, chemical abundances, and transverse sizes of a multiphase medium in a galaxy field at z = 0.399. The angular separation between the quasars corresponds to a physical separation of 520 kpc at the absorber redshift. The absorber towards Q 0107–025B is a partial Lyman limit system (pLLS) with $\log N({\mathrm{H}}{\small I})/\hbox{cm$^{-2}$}\approx 16.8$. The H i column density in the absorber along the other sightline is ≈ 2 orders of magnitude lower. The O vi along both sightlines have comparable column densities and broad b-values (b > 30 km s−1) whereas the low ionization lines are considerably narrower. The low ionization gas is inconsistent with the O vi when modelled assuming photoionization from the same phase. In both lines of sight, O vi and the broad H i coinciding, are best explained through collisional ionization in a cooling plasma with solar metallicity. Ionization models infer 1/10th solar metallicity for the pLLS and solar metallicity for the lower column density absorber along the other sightline. Within ± 250 km s−1 and 2 Mpc of projected distance from the sightlines 12 galaxies are identified, of which five are within 500 kpc. The twin sightlines are at normalized impact parameters of ρ ∼ 1.1Rvir, and ρ ∼ 0.8Rvir from a M* ∼ 1010.7 M⊙, L ∼ 0.07L*, and star formation rate (SFR) < 0.1 M⊙ yr−1 galaxy, potentially probing its CGM (circumgalactic medium). The next closest in normalized separation are a dwarf galaxy with M* ∼ 108.7 M⊙, and SFR ∼ 0.06 M⊙ yr−1, and an intermediate mass galaxy with M* ∼ 1010.0 M⊙, and SFR ∼ 3 M⊙ yr−1. Along both sightlines, O vi could be either tracing narrow transition temperature zones at the interface of low ionization gas and the hot halo of nearest galaxy, or a more spread-out warm component that could be gas bound to the circumgalactic halo or the intragroup medium. The latter scenarios lead to a warm gas mass limit of M ≳ 4.5 × 109 M⊙.

Download Full-text

Comparing Chemical Abundances of the Damped Lyα Systems and Metal-Poor Stars

Highlights of Astronomy ◽

10.1017/s1539299600016543 ◽

2005 ◽

Vol 13 ◽

pp. 536-541

Author(s):

Jason X. Prochaska

Keyword(s):

Dwarf Galaxy ◽

Chemical Abundances ◽

Stellar Abundances ◽

Abundance Patterns

AbstractI briefly draw comparisons between the fields of damped Lyα and metal-poor stellar abundances. In particular, I examine their complementary age-metallicity relations and comparisons between the damped Lyα and dwarf galaxy abundance patterns. Regarding the latter, I describe a series of problems concerning associating high z damped Lyα systems with present-day dwarfs.

Download Full-text

Ionized and neutral gas in the XUV discs of nearby spiral galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314009326 ◽

2014 ◽

Vol 10 (S309) ◽

pp. 65-68

Author(s):

López-Sánchez ◽

B. S. Koribalski ◽

T. Westmeier ◽

C. Esteban

Keyword(s):

Spiral Galaxies ◽

Dwarf Galaxy ◽

Chemical Abundances ◽

Ionized Gas ◽

Galaxy Interactions ◽

Star Forming ◽

Star Forming Regions ◽

Neutral Gas ◽

The Galaxy ◽

Nearby Galaxies

AbstractWe are conducting a multiwavelength study of XUV discs in nearby, gas-rich spiral galaxies combining the available UV (GALEX) observations with H i data obtained at the ATCA as part of the Local Volume HI Survey (LVHIS) project and multi-object fibre spectroscopy obtained using the 2dF/AAOmega instrument at the 3.9m AAT. Here we present the results of the multiwavelength analysis of the galaxy pair NGC 1512/1510. The H i distribution of NGC 1512 is very extended with two pronounced spiral/tidal arms. Hundreds of independent UV-bright regions are associated with dense H i clouds in the galaxy outskirts. We confirm the detection of ionized gas in the majority of them and characterize their physical properties, chemical abundances and kinematics. Both the gas distribution andthe distribution of the star-forming regions are affected by gravitational interactionwith the neighbouring blue compact dwarf galaxy NGC 1510. Our multiwavelength analysis provides new clues about local star-formation processes, the metal redistribution in the outer gaseous discs of spiral galaxies, the importance of galaxy interactions, the fate of the neutral gas and the chemical evolution in nearby galaxies.

Download Full-text

Influence of the Void Environment on Chemical Abundances in Dwarf Galaxies and Implications for Connecting Star Formation and Halo Mass

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318006816 ◽

2018 ◽

Vol 14 (S344) ◽

pp. 369-372

Author(s):

Kelly A. Douglass ◽

Michael S. Vogeley ◽

Renyue Cen

Keyword(s):

Dark Matter ◽

Star Formation ◽

Large Scale ◽

Dwarf Galaxies ◽

Dwarf Galaxy ◽

Direct Method ◽

Dark Matter Halo ◽

Chemical Abundances ◽

Abundance Estimates ◽

Galaxy Populations

AbstractWe study how the void environment affects the chemical evolution of galaxies by comparing the metallicity of dwarf galaxies in voids with dwarf galaxies in denser regions. Using spectroscopic observations from SDSS DR7, we estimate oxygen and nitrogen abundances of 889 void dwarf galaxies and 672 dwarf galaxies in denser regions. A substitute for the [OII] λ3727 doublet is developed, permitting oxygen abundance estimates of SDSS dwarf galaxies at all redshifts with the direct method. We find that void dwarf galaxies have about the same oxygen abundances and slightly lower N/O ratios than dwarf galaxies in denser environments. The lower N/O ratios seen in void dwarf galaxies may indicate both delayed star formation and a dependence of cosmic downsizing on the large-scale environment. Similar oxygen abundances in the two dwarf galaxy populations might be evidence of larger ratios of dark matter halo mass to stellar mass in voids.

Download Full-text

Evidence for ≳4 Gyr timescales of neutron star mergers from Galactic archaeology

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937293 ◽

2020 ◽

Vol 634 ◽

pp. L2 ◽

Cited By ~ 1

Author(s):

Á. Skúladóttir ◽

S. Salvadori

Keyword(s):

Neutron Star ◽

Milky Way ◽

Dwarf Galaxy ◽

Direct Detection ◽

Compact Object ◽

Core Collapse ◽

Chemical Abundances ◽

Capture Process ◽

Process Elements ◽

First Time

The nucleosynthetic site of the rapid (r) neutron-capture process is currently being debated. The direct detection of the neutron star merger GW170817, through gravitational waves and electromagnetic radiation, has confirmed such events as important sources of the r-process elements. However, chemical evolution models are not able to reproduce the observed chemical abundances in the Milky Way when neutron star mergers are assumed to be the only r-process site and realistic time distributions of such events are taken into account. Now for the first time, we combine all the available observational evidence of the Milky Way and its dwarf galaxy satellites to show that the data can only be explained if there are (at least) two distinct r-process sites: a quick source with timescales comparable to core-collapse supernovae, tquick ≲ 108 yr, and a delayed source with characteristic timescales tdelayed ≳ 4 Gyr. The delayed r-process source most probably originates in neutron star mergers, as the timescale fits well with that estimated for GW170817. Given the short timescales of the quick source, it is likely associated with massive stars, though a specific fast-track channel for compact object mergers cannot be excluded at this point. Our approach demonstrates that only by looking at all the available data will we be able to solve the puzzle that is the r-process.

Download Full-text

Lithium and beryllium in the Gaia-Enceladus galaxy

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1653 ◽

2020 ◽

Vol 496 (3) ◽

pp. 2902-2909

Author(s):

P Molaro ◽

G Cescutti ◽

X Fu

Keyword(s):

Milky Way ◽

Local Group ◽

Galactic Halo ◽

Dwarf Galaxy ◽

Chemical Abundances ◽

Dwarf Stars ◽

Evolution Experiment ◽

External Galaxies ◽

Low Metallicity ◽

Gaia Dr2

ABSTRACT Data from Gaia DR2 and The Apache Point Observatory Galactic Evolution Experiment surveys revealed a relatively new component in the inner Galactic halo, which is likely the dynamical remnant of a disrupted dwarf galaxy named Gaia-Enceladus that collided with the Milky Way about 10 Gyr ago. This merging event offers an extraordinary opportunity to study chemical abundances of elements in a dwarf galaxy, since they are generally hampered in external galaxies. Here, we focus on 7Li and 9Be in dwarf stars that are out of reach even in Local Group galaxies. Searching in GALAH, Gaia-ESO survey and in literature, we found several existing 7Li abundance determinations of stars belonging to the Gaia-Enceladus galaxy. The 7Li abundances of stars at the low metallicity end overlap with those of the Galactic halo. These are effective extragalactic 7Li measurements, which suggest that the 7Li Spite plateau is universal, as is the cosmological 7Li problem. We found a 7Li-rich giant out of 101 stars, which suggests a small percentage similar to that of the Milky Way. We also collect 9Be abundance for a subsample of 25 Gaia-Enceladus stars from literature. Their abundances share the Galactic [Be/H] values at the low metallicity end but grow slower with [Fe/H] and show a reduced dispersion. This suggests that the scatter observed in the Milky Way could reflect the different 9Be evolution patterns of different stellar components that are mixed-up in the Galactic halo.

Download Full-text