The extended structure of the dwarf irregular galaxy Sagittarius

Beccari, G.; Bellazzini, M.; Fraternali, Filippo; Battaglia, G.; Perina, S.; Sollima, A.; Oosterloo, Tom; Testa, V.; Galleti, S.

doi:10.1051/0004-6361/201424411

Cited by 17 publications

(31 citation statements)

References 52 publications

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“…This result is in agreement with recent estimates by Momany et al (2002) ((m − M )0 = 25.14 ± 0.18) and Momany et al (2005) ((m − M )0 = 25.10 ± 0.11), which implement different reddening corrections, also including internal extinction. It is also in agreement with the most recent estimate by Beccari et al (2014), finding (m − M )0 = 25.56±0.11.…”

Section: Distance Estimatesupporting

confidence: 93%

“…HI structure has been analyzed in detail previously by Lo et al (1993), Young & Lo (1997) and Beccari et al (2014) and it is interesting to compare this structure with our extended stellar maps. Figure 12 shows the integrated HI map of Sag DIG from the LITTLE THINGS Survey (Hunter et al 2012) in comparison to the RGB stellar distribution discussed previously.…”

Section: On the Content And Structure Of Sag Digmentioning

confidence: 83%

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Solo dwarfs I: survey introduction and first results for the Sagittarius dwarf irregular galaxy

Higgs¹,

McConnachie²,

Irwin³

et al. 2016

Mon. Not. R. Astron. Soc.

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We introduce the Solitary Local Dwarfs Survey (Solo), a wide field photometric study targeting every isolated dwarf galaxy within 3 Mpc of the Milky Way. Solo is based on (u)gi multi-band imaging from CFHT/MegaCam for northern targets, and Magellan/Megacam for southern targets. All galaxies fainter than M V −18 situated beyond the nominal virial radius of the Milky Way and M31 ( 300 kpc) are included in this volume-limited sample, for a total of 42 targets. In addition to reviewing the survey goals and strategy, we present results for the Sagittarius Dwarf Irregular Galaxy (Sag DIG), one of the most isolated, low mass galaxies, located at the edge of the Local Group. We analyze its resolved stellar populations and their spatial distributions. We provide updated estimates of its central surface brightness and integrated luminosity, and trace its surface brightness profile to a level fainter than 30 mag./sq.arcsec. Sag DIG is well described by a highly elliptical (disk-like) system following a single component Sersic model. However, a low-level distortion is present at the outer edges of the galaxy that, were Sag DIG not so isolated, would likely be attributed to some kind of previous tidal interaction. Further, we find evidence of an extremely low level, extended distribution of stars beyond ∼ 5 arcmins (> 1.5 kpc) that suggests Sag DIG may be embedded in a very low density stellar halo. We compare the stellar and HI structures of Sag DIG, and discuss results for this galaxy in relation to other isolated, dwarf irregular galaxies in the Local Group.

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Section: Distance Estimatesupporting

confidence: 93%

Section: On the Content And Structure Of Sag Digmentioning

confidence: 83%

Solo dwarfs I: survey introduction and first results for the Sagittarius dwarf irregular galaxy

Higgs¹,

McConnachie²,

Irwin³

et al. 2016

Mon. Not. R. Astron. Soc.

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“…This effect can eventually lead to an overall median age gradient where young stars form in the center of the galaxy and old stars are preferentially found in the outskirts. Qualitatively, this agrees with the observed age and metallicity gradients seen in most dwarf galaxies locally, where younger (more metal-rich) stars lie in the center and older (more metal-poor) stars in the outskirts (Battaglia et al 2006;Faria et al 2007;Beccari et al 2014;McMonigal et al 2014;del Pino et al 2015;Santana et al 2016;Kacharov et al 2017;McQuinn et al 2017;Okamoto et al 2017;Cicuéndez et al 2018;Cicuéndez & Battaglia 2018).…”

supporting

confidence: 88%

A predicted correlation between age gradient and star formation history in FIRE dwarf galaxies

Graus

Bullock

Fitts

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We explore the radial variation of star formation histories in dwarf galaxies simulated with Feedback In Realistic Environments (FIRE) physics. The sample contains 9 lowmass field dwarfs with M star = 10 5 − 10 7 M from previous FIRE results, and a new suite of 17 higher mass field dwarfs with M star = 10 7 − 10 9 M introduced here. We find that age gradients are common in our dwarfs, with older stars dominant at large radii. The strength of the gradient correlates with overall galaxy age such that earlier star formation produces a more pronounced gradient. The relation between formation time and strength of the gradient is driven by both mergers and star-formation feedback. Mergers can both steepen and flatten the age gradient depending on the timing of the merger and star formation history of the merging galaxy. In galaxies without significant mergers, early feedback pushes stars to the outskirts at early times. Interestingly, among galaxies without mergers, those with large dark matter cores have flatter age gradients because these galaxies have more late-time feedback. If real galaxies have age gradients as we predict, stellar population studies that rely on sampling a limited fraction of a galaxy can give a biased view of its global star formation history. We show that central fields can be biased young by a few Gyrs while outer fields are biased old. Fields positioned near the 2D half-light radius will provide the least biased measure of a dwarf galaxy's global star formation history.

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“…The surface brightness profile drops exponentially out to 5′, at which point it fades into the background (Beccari et al 2014). The galaxy may even be embedded in a very low density stellar halo (Higgs et al 2016).…”

Section: Sagdigmentioning

confidence: 99%

Chemistry and Kinematics of the Late-Forming Dwarf Irregular Galaxies Leo A, Aquarius, and Sagittarius Dig*

Kirby

Rizzi

Held

et al. 2016

ApJ

100

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We present Keck/DEIMOS spectroscopy of individual stars in the relatively isolated Local Group dwarf galaxies LeoA, Aquarius, and the Sagittarius dwarf irregular galaxy. The three galaxies-but especially LeoA and Aquarius-share in common delayed star formation histories (SFHs) relative to many other isolated dwarf galaxies. The stars in all three galaxies are supported by dispersion. We found no evidence of stellar velocity structure, even for Aquarius, which has rotating H I gas. The velocity dispersions indicate that all three galaxies are dark-matter-dominated, with dark-to-baryonic mass ratios ranging from -+ 4.4 0.8 1.0 (SagDIG) to -+ 9.6 1.8 2.5 (Aquarius). LeoA and SagDIG have lower stellar metallicities than Aquarius, and they also have higher gas fractions, both of which would be expected if Aquarius were further along in its chemical evolution. The metallicity distribution of LeoA is inconsistent with a closed or leaky box model of chemical evolution, suggesting that the galaxy was preenriched or acquired external gas during star formation. The metallicities of stars increased steadily for all three galaxies, but possibly at different rates. The [α/Fe] ratios at a given [Fe/H] are lower than that of the Sculptor dwarf spheroidal galaxy, which indicates more extended SFHs than Sculptor, consistent with photometrically derived SFHs. Overall, the bulk kinematic and chemical properties for the late-forming dwarf galaxies do not diverge significantly from those of less delayed dwarf galaxies, including dwarf spheroidal galaxies.

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The extended structure of the dwarf irregular galaxy Sagittarius

Cited by 17 publications

References 52 publications

Solo dwarfs I: survey introduction and first results for the Sagittarius dwarf irregular galaxy

Solo dwarfs I: survey introduction and first results for the Sagittarius dwarf irregular galaxy

A predicted correlation between age gradient and star formation history in FIRE dwarf galaxies

Chemistry and Kinematics of the Late-Forming Dwarf Irregular Galaxies Leo A, Aquarius, and Sagittarius Dig*

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