The variability of carbon stars in the Sagittarius dwarf spheroidal galaxy

Battinelli, P.; Demers, S.

doi:10.1051/0004-6361/201321059

Cited by 8 publications

(17 citation statements)

References 41 publications

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“…Their presence, however, is a reminder of our poor understanding of the thermal pulsating AGB phase and the carbon-rich to oxygen-rich transition. Overall, the SagDIG proper-motion based carbon/oxygen ratio is consistently within the Battinelli & Demers (2013) reported error. Being the most metal-poor galaxy in the Battinelli & Demers (2013) sample, SagDIG plays an important role in establishing the zero point of the [Fe/H]-log (C/M0+) anti-correlation.…”

Section: Discussionsupporting

confidence: 78%

The H i hole and AGB stellar population of the Sagittarius dwarf irregular galaxy

Momany

Clemens

Bedin

et al. 2014

A&A

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Using two HST/ACS data sets that are separated by about two years has allowed us to derive the relative proper motion for the Sagittarius dwarf irregular (SagDIG) and reduce the heavy foreground Galactic contamination. The proper-motion decontaminated SagDIG catalog provides a much clearer view of the young red-supergiant and intermediate-age asymptotic giant branch populations. Previously identified carbon-and oxygen-rich star samples, which are based on narrow-band filter photometry, were complemented by membership criteria. We report identifying three Milky Way carbon-rich dwarf stars, which probably belong to the thin disk, and pointing to the high incidence of this class at low Galactic latitudes. A subgroup of four oxygen-rich candidate stars depicts a faint, red extension of the well-defined SagDIG carbon-rich sequence. The origin of these oxygen-rich candidate stars remains unclear, reflecting the uncertainty in the ratio of carbon-and oxygen-rich stars. Finally, SagDIG is a gas-rich galaxy characterized by a single large cavity in the gas disk (H  hole), which is offset by ∼360 pc from the optical center of the galaxy. We nonetheless investigate the stellar feedback hypothesis by comparing the proper-motion cleaned stellar populations within the H  hole with appropriately selected comparison regions that have higher H  densities external to the hole. The comparison shows no significant differences. In particular, the center of the H  hole (and the comparison regions) lack stellar populations younger than ∼400 Myr, which are otherwise abundant in the inner body of the galaxy. We conclude that there is no convincing evidence that the SagDIG H  hole is the result of stellar feedback and that gravitational and thermal instabilities in the gas are the most likely mechanism for its formation.

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Section: Discussionsupporting

confidence: 78%

The H i hole and AGB stellar population of the Sagittarius dwarf irregular galaxy

Momany

Clemens

Bedin

et al. 2014

A&A

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“…Not all of the latter objects are spectroscopically confirmed C stars, but their near-infrared colours strongly favour this chemistry. One object of Battinelli & Demers (2013), called Sgr 13 (2MASS J185329.37−293824.1), is also in the list of Whitelock et al (1999), and the period determinations agree. In the end, 22 Miras and two SRs are known with periods available.…”

Section: Comparison With Sagittariusmentioning

confidence: 84%

“…Four C-rich Miras and one SR in Sgr have been reported by Whitelock et al (1999) with measured periods, and six other C Miras were found by Lagadec et al (2009). Recently, Battinelli & Demers (2013) identified and monitored 13 Miras and one SR in Sgr. Not all of the latter objects are spectroscopically confirmed C stars, but their near-infrared colours strongly favour this chemistry.…”

Section: Comparison With Sagittariusmentioning

confidence: 90%

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Cool carbon stars in the halo and in dwarf galaxies: Hα, colours, and variability

Mauron

Gigoyan

Berlioz-Arthaud

et al. 2014

A&A

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The population of cool carbon (C) stars located far from the galactic plane is probably made of debris of small galaxies such as the Sagittarius dwarf spheroidal galaxy (Sgr), which are disrupted by the gravitational field of the Galaxy. We aim to know this population better through spectroscopy, 2MASS photometric colours, and variability data. When possible, we compared the halo results to C star populations in the Fornax dwarf spheroidal galaxy, Sgr, and the solar neighbourhood. We first present a few new discoveries of C stars in the halo and in Fornax. The number of spectra of halo C stars is now 125. Forty percent show Hα in emission. The narrow location in the JHK diagram of the halo C stars is found to differ from that of similar C stars in the above galaxies. The light curves of the Catalina and LINEAR variability databases were exploited to derive the pulsation periods of 66 halo C stars. A few supplementary periods were obtained with the TAROT telescopes. We confirm that the period distribution of the halo strongly resembles that of Fornax, and we found that it is very different from the C stars in the solar neighbourhood. There is a larger proportion of short-period Mira/SRa variables in the halo than in Sgr, but the survey for C stars in this dwarf galaxy is not complete, and the study of their variability needs to be continued to investigate the link between Sgr and the cool halo C stars.

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“…We can check this relation using the sample of Battinelli & Demers (2013), who obtained J and K light curves for many of the Mauron group stars, and so overlap our first sample. We see that the fits are comparable, although both show some considerable scatter (Fig.…”

Section: Distance Determination and Uncertainties On Distancesmentioning

confidence: 99%

Tracing the tidal streams of the Sagittarius dSph, and halo Milky Way features, with carbon-rich long-period variables

Huxor

Grebel

2015

Mon. Not. R. Astron. Soc.

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We assemble 121 spectroscopically-confirmed halo carbon stars, drawn from the literature, exhibiting measurable variability in the Catalina Surveys. We present their periods and amplitudes, which are used to estimate distances from period-luminosity relationships. The location of the carbon stars -and their velocities when availableallow us to trace the streams of the Sagittarius (Sgr) dwarf spheroidal galaxy. These are compared to a canonical numerical simulation of the accretion of Sgr. We find that the data match this model well for heliocentric distances of 15-50 kpc, except for a virtual lack of carbon stars in the trailing arm just north of the Galactic Plane, and there is only tentative evidence of the leading arm south of the Plane. The majority of the sample can be attributed to the Sgr accretion. We also find groups of carbon stars which are not part of Sgr; most of which are associated with known halo substructures. A few have no obvious attribution and may indicate new substructure. We find evidence that there may be a structure behind the Sgr leading stream apocentre, at ∼100 kpc, and a more distant extension to the Pisces Overdensity also at ∼100 kpc. We study a further 75 carbon stars for which no good period data could be obtained, and for which NIR magnitudes and colours are used to estimate distances. These data add support for the features found at distances beyond 100 kpc.

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The variability of carbon stars in the Sagittarius dwarf spheroidal galaxy

Cited by 8 publications

References 41 publications

The H i hole and AGB stellar population of the Sagittarius dwarf irregular galaxy

The H i hole and AGB stellar population of the Sagittarius dwarf irregular galaxy

Cool carbon stars in the halo and in dwarf galaxies: Hα, colours, and variability

Tracing the tidal streams of the Sagittarius dSph, and halo Milky Way features, with carbon-rich long-period variables

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