RR Lyrae stars in the Sagittarius dwarf galaxy: Period analysis

Cseresnjes, P.

doi:10.1051/0004-6361:20010863

Cited by 64 publications

(84 citation statements)

References 62 publications

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“…, to support the Newberg et al (2003) suggestion r ∼ 15 of a past association with the Sgr dSph, a claim also disfavored by the Sgr field and cluster (M54) RR Lyrae stars having properties on the long-period tail of the OoI group and intermediate between Oosterhoff types, respectively (Cseresnjes 2001;Cacciari et al 2002). From our data, NGC 2419 appears indeed to be a very normal, low-metallicity GGC, the only exception being the HB blue hook, a feature detected so far only in very few globulars and, most noteworthy, in those showing multiple main sequences and/or of likely extragalactic origin: NGC 2808 (Piotto et al 2007), q Cen (Villanova et al 2007), and M54 (Layden & Sarajedini 2000).…”

Section: Yondmentioning

confidence: 84%

On the Remote Galactic Globular Cluster NGC 2419

Ripepi

Clementini

Criscienzo

et al. 2007

ApJ

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We present a new, deep ( ) study of the Galactic globular cluster NGC 2419 based on B, V, I time-series V ∼ 26 CCD photometry over about 10 years and extending beyond the cluster published tidal radius. We have identified 101 variable stars, of which 60 are new discoveries, doubling the known RR Lyrae stars and including 12 SX Phoenicis stars. The average period of the RR Lyrae stars ( 2 days and days, for AP S p 0.66 AP S p 0.366fundamental-mode-RRab-and first-overtone pulsators, respectively) and the position in the period-amplitude diagram both confirm that NGC 2419 is an Oosterhoff II cluster. q Cen hosts multiple stellar populations (see, e.g., Bedin et al. 2004;Rey et al. 2004;Sollima et al. 2005) and likely is the stripped core of a defunct dwarf galaxy (Villanova et al. 2007 and references therein); and M54 is thought to be the core of the Sagittarius (Sgr) dwarf spheroidal galaxy (dSph), which is currently merging with the MW (see, e.g., Layden & Sarajedini 2000). All these peculiarities and the similarity with q Cen and M54 suggest that NGC 2419 could have an extragalactic origin and be the relict of a dwarf galaxy tidally disrupted by the MW (van den Bergh & Mackey 2004). Newberg et al. (2003) find that the cluster appears to lie within an overdensity of A-type stars connected to previously discovered tidal tails of the Sgr dSph and conclude that the cluster might once have been associated to Sgr. In addition, the cluster has a central velocity dispersion ( ) much lower than the dSph's for which this j 0 quantity has been measured and, in the versus plane log j M 0 V (Faber & Jackson 1976), lies 3 and 6 j apart from the "fundamental plane" relations for GCs and elliptical galaxies, respectively (see de Grijs et al. 2005). For a comparison, in this plane q Cen lies at the intersection of these two lines. Color-magnitude diagrams (CMDs) of NGC 2419 published so far either do not go fainter than the main-sequence turnoff (TO) or cover small portions of the cluster (Christian & Heasley 1988;Harris et al. 1997;Stetson 1998Stetson , 2005Saha et al. 2005;Sirianni et al. 2005). We also lack a modern study of the cluster variable stars based on accurate CCD photometry, the most recent variability survey being the photographic work by Pinto & Rosino (1977, hereafter PR), who detected 41 variables in the external regions of NGC 2419 and found the average period of the fundamental-mode RR Lyrae (RRab) stars to be consistent with NGC 2419 being an Oosterhoff II (OoII) cluster (Oosterhoff 1939).In this Letter, we present a CMD reaching about 2.6 mag below the NGC 2419 TO and a new study of the variable stars L62 RIPEPI ET AL.Vol. 667

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Section: Yondmentioning

confidence: 84%

On the Remote Galactic Globular Cluster NGC 2419

Ripepi

Clementini

Criscienzo

et al. 2007

ApJ

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“…With the transformation equation in Odenkirchen et al (2001), this value yields (V À i) 0 ¼ 0:4, which we added to the value of M i ¼ À8:77 AE 0:2 (Odenkirchen et al 2001). For the Sagittarius dSph, we adopted the M V that Cseresnjes (2001) derived, which lies near the middle of the range quoted in the recent literature. The values of the mean [Fe/H] of the galaxies were taken from Mateo (1998) for the Milky Way companions and from Pritzl et al (2002Pritzl et al ( , 2004Pritzl et al ( , 2005 for the Andromeda satellite galaxies.…”

Section: The Population Bias Of An Rrls Surveymentioning

confidence: 99%

“…Pritzl et al (2002Pritzl et al ( , 2004Pritzl et al ( , 2005 estimated the fractions of the luminosities of the And galaxies that were covered by their fields, which made the calculations of N est straightforward. For the Sgr dSph galaxy, we adopted the estimate by Cseresnjes (2001) that its main body contains 4200 type ab RR Lyrae variables. We then used the observed ratio of the type c to type ab RRLSs to derive N est .…”

Section: The Population Bias Of An Rrls Surveymentioning

confidence: 99%

The QUEST RR Lyrae Survey. II. The Halo Overdensities in the First Catalog

Vivas¹,

Zinn

2006

164

146

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The first catalog of the RR Lyrae stars (RRLSs) in the Galactic halo by the Quasar Equatorial Survey Team (QUEST ) has been searched for significant overdensities that may be debris from disrupted dwarf galaxies or globular clusters. These RRLSs are contained in a band $2N3 wide in declination that spans $165 in right ascension and lie $4 to $60 kpc from the Sun. Away from the major overdensities, the distribution of these stars is adequately fitted by a smooth halo model, in which the flattening of the halo decreases with increasing galactocentric distance (as reported by Preston et al.). This model was used to estimate the ''background'' of RRLSs on which the halo overdensities are overlaid. A procedure was developed for recognizing groups of stars that constitute significant overdensities with respect to this background. To test this procedure, a Monte Carlo routine was used to make artificial RRLS surveys that follow the smooth halo model but with Poisson-distributed noise in the numbers of RRLSs and, within limits, random variations in the positions and magnitudes of the artificial stars. The 10 4 artificial surveys created by this routine were examined for significant groups in exactly the same way as the QUEST survey. These calculations provided estimates of the frequencies with which random fluctuations produce significant groups. In the QUEST survey there are six significant overdensities that contain six or more stars and several smaller ones. The small ones and possibly one or two of the larger ones may be artifacts of statistical fluctuations, and they need to be confirmed by measurements of radial velocity and/or proper motion. The most prominent groups are the northern stream from the Sagittarius dwarf spheroidal galaxy and a large group in Virgo, formerly known as the ''12.4 hr clump,'' which Duffau and coworkers have recently shown to contain a stellar stream (the Virgo stellar stream). Two other groups lie in the direction of the Monoceros stream and at approximately the right distance for membership. Another group is related to the globular cluster Palomar 5.

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“…Fig. 9a in Cseresnjes 2001). Differences in period distributions (e.g., mean period and width) are also known to occur in Galactic sub-systems and satellite galaxies.…”

Section: Introductionmentioning

confidence: 96%

“…Differences in period distributions (e.g., mean period and width) are also known to occur in Galactic sub-systems and satellite galaxies. For example, while period distributions are quite similar e-mail: butler@mpia.de in some systems (e.g., Sgr and the Large Magellanic Cloud) they are significantly different in others: e.g., compare Sgr with Carina, Leo II or M 15 for instance (Cseresnjes 2001). Do differences occur within any galactic globular clusters?…”

Section: Introductionmentioning

confidence: 99%