- ID:
- ivo://CDS.VizieR/J/ApJ/784/76
- Title:
- RR Lyrae variables in ESO294-G010 and ESO410-G005
- Short Name:
- J/ApJ/784/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of our analysis of the RR Lyrae (RRL) variable stars detected in two transition-type dwarf galaxies (dTrans), ESO294-G010 and ESO410-G005 in the Sculptor group, which is known to be one of the closest neighboring galaxy groups to our Local Group. Using deep archival images from the Advanced Camera for Surveys on board the Hubble Space Telescope, we have identified a sample of RRL candidates in both dTrans galaxies (219 RRab (RR0) and 13 RRc (RR1) variables in ESO294-G010; 225 RRab and 44 RRc stars in ESO410-G005). The metallicities of the individual RRab stars are calculated via the period-amplitude-[Fe/H] relation derived by Alcock et al. This yields mean metallicities of <[Fe/H]>_ESO294_=-1.77+/-0.03 and <[Fe/H]>_ESO410_=-1.64+/-0.03. The RRL metallicity distribution functions (MDFs) are investigated further via simple chemical evolution models; these reveal the relics of the early chemical enrichment processes for these two dTrans galaxies. In the case of both galaxies, the shapes of the RRL MDFs are well described by pre-enrichment models. This suggests two possible channels for the early chemical evolution for these Sculptor group dTrans galaxies: (1) the ancient stellar populations of our target dwarf galaxies might have formed from the star forming gas which was already enriched through "prompt initial enrichment" or an "initial nucleosynthetic spike" from the very first massive stars, or (2) this pre-enrichment state might have been achieved by the end products from more evolved systems of their nearest neighbor, NGC 55. We also study the environmental effects of the formation and evolution of our target dTrans galaxies by comparing their properties with those of 79 volume limited (D_{sun}_<2Mpc) dwarf galaxy samples in terms of the luminosity-metallicity relation and the H I gas content. The presence of these RRL stars strongly supports the idea that although the Sculptor Group galaxies have a considerably different environment from the Local Group (e.g., no giant host galaxies, loosely bound and very low local density), they share a common epoch of early star formation with the dwarf satellite galaxies in the Local Group.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/138/184
- Title:
- RR Lyrae variables in 2 fields in M31 spheroid
- Short Name:
- J/AJ/138/184
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Hubble Space Telescope observations taken with the Advanced Camera for Surveys Wide Field Channel of two fields near M32 - between 4 and 6kpc from the center of M31. The data cover a time baseline sufficient for the identification and characterization of 681 RR Lyrae variables of which 555 are ab-type and 126 are c-type.
- ID:
- ivo://CDS.VizieR/J/AJ/132/1361
- Title:
- RR Lyrae variables in M33
- Short Name:
- J/AJ/132/1361
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations of RR Lyrae variables in the Local Group late-type spiral galaxy M33. Using the Advanced Camera for Surveys on the Hubble Space Telescope, we have identified 64 ab-type RR Lyrae stars in M33. We have estimated reddenings for these stars based on their minimum light V-I colors and metallicities based on their periods. From the distributions of these properties, we conclude that the RR Lyrae stars belong to two populations: one associated with the halo of M33 and the other associated with its disk. Given that RR Lyrae stars are produced by populations older than 10Gyr, this suggests that not only does the field halo of M33 contain an old component, but so does its disk. This is one of the best pieces of evidence for the existence of a halo field component in M33. Using a relation between RR Lyrae absolute magnitude and metallicity (M_V_(RR)=0.23[Fe/H]+0.93), we estimate a mean distance modulus of (m-M)0=24.67+/-0.08 for M33. This places M33 approximately 70kpc beyond M31 in line-of-sight distance.
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/870
- Title:
- RR Lyrae variables in M33
- Short Name:
- J/MNRAS/468/870
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a re-analysis of M33 RR Lyrae variables in four different fields: two inner disc fields and two outer disc fields. These are located at 8.5, 8.7, 36 and 46 arcmin from the centre of M33, respectively. We identify 48 new RR Lyrae variable stars and refine the light-curve properties of 51 previously identified variables. From the light curves, we calculate reddenings and metallicities for each star. Using data in this paper and previously published material, we are able to construct a radial density profile for the RR Lyrae stars in M33. This profile, when plotted in log space, has a slope of ~-2.0+/-0.15 which agrees with the radial distribution of halo stars in the Milky Way and M31. This suggests that the majority of M33 RR Lyrae variables observed so far belong to the halo. We also examine the RR Lyrae specific frequency and absolute magnitude relation in M33 and find good agreement with previous studies.
- ID:
- ivo://CDS.VizieR/J/AJ/110/704
- Title:
- RR Lyrae Variables in M15
- Short Name:
- J/AJ/110/704
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New CCD photometry is presented for RR Lyrae variable stars in the globular cluster M15. This photometry, mainly in V and R, with some additional B and I, is used to construct lightcurves of 44 RR Lyraes and one Cepheid in M15. One new low-amplitude RR Lyrae star was discovered. The observable parameters of the light curves are used, in conjunction with theoretical photometric indices, to obtain effective temperatures and bolometric magnitudes in the RR Lyrae stars. We confirm that the regions occupied by RRab and RRcd variables in M15 have little or no overlap in effective temperature. Photometry for variable and nonvariable horizontal branch stars in M15 is used to establish the high and low temperature boundaries of the instability strip. There is evidence that the blue edge of the M15 RR Lyrae instability strip becomes cooler at higher luminosities. Employing Cox's value of the mass of RRd stars, 0.75 Msun, and the pulsation equation, the absolute magnitude of the RR Lyrae stars in M15 is estimated to be <M_V_> = +0.36+/-0.12 mag. However, this result depends upon the adopted mass, bolometric correction, and color-temperature relation, which remain significantly uncertain. The implications of the absolute magnitude determination for the ages of the globular clusters are discussed.
- ID:
- ivo://CDS.VizieR/J/ApJ/708/817
- Title:
- RR Lyrae variables in M32 and M31
- Short Name:
- J/ApJ/708/817
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed two fields near M32 with the Advanced Camera for Surveys/High Resolution Channel (ACS/HRC) on board the Hubble Space Telescope. The main field, F1, is 1.8' from the center of M32; the second field, F2, constrains the M31 background, and is 5.4' distant. Each field was observed for 16 orbits in each of the F435W (narrow B) and F555W (narrow V) filters. The duration of the observations allowed RR Lyrae stars to be detected. A population of RR Lyrae stars determined to belong to M32 would prove the existence of an ancient population in that galaxy, a subject of some debate. We detected 17 RR Lyrae variables in F1 and 14 in F2. A 1{sigma} upper limit of 6 RR Lyrae variables belonging to M32 is inferred from these two fields alone. Use of our two ACS/WFC parallel fields provides better constraints on the M31 background, however, and implies that 7^+4^_-3_ (68% confidence interval) RR Lyrae variables in F1 belong to M32. We have therefore found evidence for an ancient population in M32. It seems to be nearly indistinguishable from the ancient population of M31. The RR Lyrae stars in the F1 and F2 fields have indistinguishable mean V-band magnitudes, mean periods, distributions in the Bailey diagram, and ratios of RRc to RRtotal types. However, the color distributions in the two fields are different, with a population of red RRab variables in F1 not seen in F2. We suggest that these might be identified with the detected M32 RR Lyrae population, but the small number of stars rules out a definitive claim.
- ID:
- ivo://CDS.VizieR/J/ApJ/724/799
- Title:
- RR Lyrae variables in M33. II.
- Short Name:
- J/ApJ/724/799
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an extensive survey of RR Lyrae (RRL) stars in three fields along the major axis of the Triangulum Galaxy (M33). From images taken with the Advanced Camera for Surveys (ACS) Wide Field Channel on board the Hubble Space Telescope through two passbands (F606W and F814W), we have identified and characterized a total of 119 RRL variables (96 RRab (RR0) and 23 RRc (RR1)) in M33. Using the properties of 83 RRL stars (65 RRab and 18 RRc) in the innermost ACS field (hereafter DISK2), we find mean periods of <P_ab_>=0.553+/-0.008(error1)+/-0.05(error2) and <P_c_>=0.325+/-0.008(error1)+/-0.05(error2), where the "error1" value represents the standard error of the mean and the "error2" value is based on the error of an individual RRL period calculated from our synthetic light curve simulations. The VI minimum-light colors of the RRab stars are used to calculate a mean line-of-sight reddening toward the DISK2 field of <E(V-I)>=0.175.
- ID:
- ivo://CDS.VizieR/J/AJ/129/267
- Title:
- RR Lyrae variables in NGC 5272
- Short Name:
- J/AJ/129/267
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a detailed study of the pulsational and evolutionary characteristics of 133 RR Lyrae stars in the globular cluster NGC 5272 (M3) using highly accurate BVI data taken on five separate epochs.
- ID:
- ivo://CDS.VizieR/J/AJ/140/1500
- Title:
- RR Lyrae variables in the central region of M54
- Short Name:
- J/AJ/140/1500
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analyzed archival Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) observations of the central region of the globular cluster M54. The 12 irregularly timed observations (6 F555W, 6 F814W) were reduced using the HSTphot stellar photometry package. Our statistical analysis of the HSTphot photometry yielded 50 variable stars that are likely RR Lyrae candidates. These candidates were missed by previous ground-based searches for RR Lyraes due to the extreme crowding in the core of M54. We performed two checks on our sample of RR Lyrae candidates to determine how different they were from the other variable candidates.
- ID:
- ivo://CDS.VizieR/J/ApJ/861/23
- Title:
- RR Lyrae variables in the Crater II dwarf galaxy
- Short Name:
- J/ApJ/861/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of RR Lyrae variable stars in Crater II, a recently discovered large and diffuse satellite dwarf galaxy of the Milky Way (MW). Based on B, V time-series photometry obtained with the Korea Microlensing Telescope Network 1.6m telescope at Cerro Tololo Inter-American Observatory, we identified 83 ab-type and 13 c-type pulsators by fitting template light curves. The detected RR Lyrae stars are centrally concentrated, which ensures that most of them are members of Crater II. In terms of the distribution of RRab stars in the period-amplitude diagram, Crater II is clearly different from ultra-faint dwarf (UFD) galaxies, but very similar to the two classical MW dwarf spheroidal (dSph) galaxies Draco and Carina with Oosterhoff-intermediate (Oo-int) properties. Combined with the mean period of ab-type variables (<P_ab_>=0.631+/-0.004days) and the c-type fraction (~0.14) in Crater II, this suggests an Oo-int classification for Crater II and implies that its nature is more like a dSph rather than a UFD. We also estimated the mean metallicity, reddening, and distance of Crater II, from the photometric and pulsation properties of the RR Lyrae stars. The stellar population model we have constructed indicates that Crater II is dominated by an old population, but is relatively younger than the oldest globular clusters in the MW. With a lack of high-amplitude short-period RRab stars, Crater II, like most of the other less massive dSphs, is probably not a surviving counterpart of the major building blocks of the MW halo.
