- 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.
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Search Results
- 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/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/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.
- ID:
- ivo://CDS.VizieR/J/A+A/539/A138
- Title:
- RR Lyr variable stars in M32
- Short Name:
- J/A+A/539/A138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using archival multi-epoch ACS/WFC images in the F606W and F814W filters of a resolved stellar field in Local Group dwarf elliptical galaxy M 32 we have made an accurate Colour-Magnitude Diagram and a careful search for RR Lyr variable stars. We identified 416 bona fide RR Lyr stars over our field of view, and their spatial distribution shows a rising number density towards the centre of M 32. These new observations clearly confirm the tentative result of Fiorentino et al. (2010ApJ...708..817F), on a much smaller field of view, associating an ancient population of RR Lyr variables to M 32. We associate at least 83 RR Lyr stars in our field to M 32.
- ID:
- ivo://CDS.VizieR/J/ApJ/826/224
- Title:
- RSG and foreground candidates in M31
- Short Name:
- J/ApJ/826/224
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the red supergiant (RSG) population of M31, obtaining the radial velocities of 255 stars. These data substantiate membership of our photometrically selected sample, demonstrating that Galactic foreground stars and extragalactic RSGs can be distinguished on the basis of B-V, V-R two-color diagrams. In addition, we use these spectra to measure effective temperatures and assign spectral types, deriving physical properties for 192 RSGs. Comparison with the solar metallicity Geneva evolutionary tracks indicates astonishingly good agreement. The most luminous RSGs in M31 are likely evolved from 25-30 M_{sun}_ stars, while the vast majority evolved from stars with initial masses of 20 M_{sun}_ or less. There is an interesting bifurcation in the distribution of RSGs with effective temperatures that increases with higher luminosities, with one sequence consisting of early K-type supergiants, and with the other consisting of M-type supergiants that become later (cooler) with increasing luminosities. This separation is only partially reflected in the evolutionary tracks, although that might be due to the mis-match in metallicities between the solar Geneva models and the higher-than-solar metallicity of M31. As the luminosities increase the median spectral type also increases; i.e., the higher mass RSGs spend more time at cooler temperatures than do those of lower luminosities, a result which is new to this study. Finally we discuss what would be needed observationally to successfully build a luminosity function that could be used to constrain the mass-loss rates of RSGs as our Geneva colleagues have suggested.
- ID:
- ivo://CDS.VizieR/J/AJ/123/2511
- Title:
- RV photometry of Draco dwarf spheroidal galaxy
- Short Name:
- J/AJ/123/2511
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This article studies the structure of the Draco dwarf spheroidal galaxy, with an emphasis on the question of whether the spatial distribution of its stars has been affected by the tidal interaction with the Milky Way, using R- and V-band CCD photometry for 11 fields that are located in and around the Draco galaxy. 9 fields are in common with Piatek et al. (J/AJ/121/841); two additional fields, N1 and S1, are adjacent to the central C0 field studied by Piatek et al. in the north and south dire ctions, respectively, and extend beyond the tidal boundary along the minor axis. hese additional fields were imaged with the KPNO 0.9 m telescope using the 2048x2048 T2KA CCD chip. The article reports coordinates for the center, a position angle of the major axis, and the ellipticity. It also reports the results of searches for asymmetries in the structure of Draco. These results and searches for a "break" in the radial profile and for the presence of principal sequences of Draco in a color-magnitude diagram for regions more than 50' from the center yield no evidence that tidal forces from the Milky Way have affected the structure of Draco.
- ID:
- ivo://CDS.VizieR/J/AJ/121/841
- Title:
- RV photometry of Draco dwarf spheroidal galaxy
- Short Name:
- J/AJ/121/841
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report R- and V-band photometry derived from CCD imaging for objects in nine fields in and around the Draco dwarf spheroidal galaxy. The most distant fields are about 1.3{deg} from the center. We use these data to search for Draco stars outside of its measured tidal boundary. The search involves three methods: (1) plotting color-magnitude diagrams for individual fields, for sections of fields, and for combined fields and sections - a colour-magnitude diagram can reveal a population of Draco stars by the presence of the expected principal sequences; (2) measuring field-to-field fluctuations in the surface density of objects located near the Draco principal sequences in the color-magnitude diagram; (3) measuring intrafield fluctuations in the surface density of those objects. We find evidence for the presence of Draco stars immediately beyond the measured tidal boundary of Draco and place an upper limit on the number of such stars in more distant fields that lie close to the extension of its major axis. The best evidence is the presence of the Draco principal sequences in the color-magnitude diagram for some combined fields and sections of fields. The measurements of the field-to-field fluctuations in the stellar surface density confirm this result.
- ID:
- ivo://CDS.VizieR/J/A+A/527/A143
- Title:
- RX J105453.3+552102 cluster SDSS photometry
- Short Name:
- J/A+A/527/A143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The most accepted scenario for the origin of fossil groups is that they are galaxy associations in which the merging rate was fast and efficient. These systems have assembled half of their mass at early epoch of the Universe, subsequently growing by minor mergers, and therefore could contain a fossil record of the galaxy structure formation. We have started an observational project in order to characterize a large sample of fossil groups. In this paper we present the analysis of the fossil system RX J105453.3+552102.
