- 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.
Number of results to display per page
Search Results
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/574/A121
- Title:
- RXJ2314.9+2243 from radio to X-rays
- Short Name:
- J/A+A/574/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radio-loud narrow-line type 1 galaxies provide us with a fresh look at the blazar phenomenon, the causes of radio loudness, and the physics of jet formation. We present a multi-wavelength study of the radio-loud narrow-line type 1 quasar RX J2314.9+2243, which exhibits some remarkable multi-wavelength properties. It is among the few radio-loud narrow-line type 1 galaxies, with a tentative {gamma}-ray detection, is luminous in the infrared, and shows an exceptionally broad and blueshifted [OIII]{lambda}5007 emission-line component. In order to understand the nature of this source, we have obtained optical, UV, X-ray, and radio observations of RX J2314.9+2243.
- ID:
- ivo://CDS.VizieR/J/ApJS/217/17
- Title:
- SAFIRES: Spitzer Archival FIR Extragalactic Survey
- Short Name:
- J/ApJS/217/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Spitzer Archival Far-InfraRed Extragalactic Survey (SAFIRES). This program produces refined mosaics and source lists for all far-infrared (FIR) extragalactic data taken during the more than six years of the cryogenic operation of the Spitzer Space Telescope. The SAFIRES products consist of FIR data in two wavelength bands (70 and 160{mu}m) across approximately 180 square degrees of sky, with source lists containing far-infrared fluxes for almost 40000 extragalactic point sources. Thus, SAFIRES provides a large, robust archival far-infrared data set suitable for many scientific goals.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A153
- Title:
- SAGAN. I. New sample & multi-wavelength studies
- Short Name:
- J/A+A/642/A153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of a project called SAGAN, which is dedicated solely to the studies of relatively rare megaparsec-scale radio galaxies in the Universe, called giant radio galaxies (GRGs). We have identified 162 new GRGs primarily from the NVSS with sizes ranging from ~0.71Mpc to 2.82Mpc in the redshift range of ~0.03-0.95, of which 23 are hosted by quasars (giant radio quasars, GRQs). As part of the project SAGAN, we have created a database of all known GRGs, the GRG catalogue, from the literature (including our new sample); it includes 820 sources. For the first time, we present the multi-wavelength properties of the largest sample of GRGs. Our results establish that the distributions of the radio spectral index and the black hole mass of GRGs do not differ from the corresponding distributions of normal-sized radio galaxies (RGs). However, GRGs have a lower Eddington ratio (ER) than RGs. Using the mid-infrared data, we classified GRGs in terms of their accretion mode: either a high-power radiatively efficient high-excitation state, or a radiatively inefficient low-excitation state. We find that GRGs in high-excitation state statistically have larger sizes, stronger radio power, jet kinetic power, and higher ER than those in low-excitation state. Our analysis reveals a strong correlation between the ER and the scaled jet kinetic power, which suggests a disc-jet coupling. Our environmental study reveals that ~10% of all GRGs may reside at the centres of galaxy clusters, in a denser galactic environment, while the majority appears to reside in a sparse environment. We find that the probability of BCG as a GRG is quite low. We present new results for GRGs that range from black hole mass to large-scale environment properties. We discuss their formation and growth scenarios, highlighting the key physical factors that cause them to reach their gigantic size.
- ID:
- ivo://CDS.VizieR/J/A+A/572/A42
- Title:
- SagDIG carbon and oxygen stars
- Short Name:
- J/A+A/572/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sagittarius dwarf irregular (also known as SagDIG or UKS 1927-177) is a gas-rich, low-metallicity and star-forming galaxy, at the outskirts (D~1.1Mpc) of the Local Group. Projected relatively close to the Galactic center [(l,b)=(21.06,-16.29)] the resolved stellar populations of this galaxy reflects a strong Galactic foreground contamination, attributed to the thin and thick disk and the halo. This has so far hampered the reconstruction of its star formation and chemical enrichment history, and studies of individual stars. We have analyzed two ACS@HST data-sets (GO-9820 and GO-10472) that were collected in August 2003 and June 2005, having a ~1.85 years epoch separation. The data has allowed the derivation of the relative proper-motion for the SagDIG stellar population and reduction of the heavy foreground contamination. This provides a much clearer view of the red stellar populations (young RSG and intermediate-age AGB as well as the old RGB and AGB). The ACS/WFC data was collected in the F475W, F606W and F814W HST filters, and the published table provides a photometric calibration of the ACS/WFC filters that follows Bedin et al. (2003AJ....126..247B). This is based on the Vega spectrum and follows the recipes given by Holtzmann et al. (1995PASP..107..156H) for WFPC2, using the most updated in-flight characterization of the camera (Sirianni et al. 2005PASP..117.1049S). Besides the reported magnitudes and their relative errors, we also provide the pixel-based offset between the two F814W epochs, which is used to separate the SagDIG stellar population from the Galactic foreground (see Sec.3 of the paper for details).
- ID:
- ivo://CDS.VizieR/J/A+A/330/453
- Title:
- Sagittarius Dwarf Galaxy VI photometry
- Short Name:
- J/A+A/330/453
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present V,I deep CCD photometry for three fields of the dwarf galaxy in Sagittarius (Sgr), located at l=5.6{deg}, b=-14.1{deg}. One of the fields is centered on the globular cluster NGC 6715 (M54), which lies in one of the dense clumps of the Sgr galaxy. Comparing the CMD of Sgr with those of globular clusters which are believed to be kinematically associated with the dwarf galaxy (Da Costa & Armandroff, 1995AJ....109.2533D), we conclude that the stellar population of Sgr presents a spread in metallicity of -0.71<=[Fe/H]<=-1.58, and that the dominant population (=~10Gyr old) is extremely similar to the star content of the associated globular cluster Terzan 7. The estimated distance to Sgr is d=~24.55Kpc.
