- ID:
- ivo://CDS.VizieR/J/MNRAS/414/3699
- Title:
- Study of hot stellar systems and galaxies
- Short Name:
- J/MNRAS/414/3699
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a complete picture of dynamically hot stellar systems, ranging from faint galaxies and star clusters of only a few hundred solar masses up to giant elliptical galaxies, in particular including large samples of compact elliptical galaxies (cEs), ultra-compact dwarf galaxies (UCDs), dwarf elliptical galaxies (dEs) of nearby galaxy clusters, and Local Group ultra-faint dwarf spheroidal galaxies (dSphs). For all those stellar systems we show the effective radius-luminosity, effective radius-stellar mass, and effective mass surface density-stellar mass plane.
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- ID:
- ivo://CDS.VizieR/J/AJ/132/447
- Title:
- Surface Brightness of 38 Gal. Globular Clusters
- Short Name:
- J/AJ/132/447
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Hubble Space Telescope (HST) allows us to study the central surface brightness profiles of globular clusters at unprecedented detail. We have mined the HST archives to obtain 38 WFPC2 images of Galactic globular clusters with adequate exposure times and filters, which we use to measure their central structure.
- ID:
- ivo://CDS.VizieR/J/AJ/143/132
- Title:
- Surface brightness profiles of 10 globulars of M31
- Short Name:
- J/AJ/143/132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present internal surface brightness profiles, using images in the F606W and F814W filter bands observed with the Advanced Camera for Surveys on the Hubble Space Telescope, for 10 globular clusters (GCs) in the outer halo of M31. Standard King models are fitted to the profiles to derive their structural and dynamical parameters. The results show that, in general, the properties of clusters in M31 and the Milky Way fall in the same regions of parameter spaces. The outer halo GCs of M31 have larger ellipticities than most of the GCs in M31 and the Milky Way. Their large ellipticities may be due to galaxy tides coming from satellite dwarf galaxies of M31 or may be related to the apparently more vigorous accretion or merger history that M31 has experienced. The tight correlation of cluster binding energy E_b_ with mass M_mod_indicates that the "fundamental plane" does exist for clusters, regardless of their host environments, which is consistent with previous studies.
- ID:
- ivo://CDS.VizieR/J/AJ/149/157
- Title:
- Surface intensity profiles for 10 M33 globular clusters
- Short Name:
- J/AJ/149/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present the properties of 10 halo globular clusters (GCs) with luminosities L~=5-7x10^5^L_{sun}_ in the Local Group galaxy M33 using images from the Hubble Space Telescope WFPC2 in the F555W and F814W bands. We obtained the ellipticities, position angles, and surface brightness profiles for each GC. In general, the ellipticities of the M33 sample clusters are similar to those of the M31 clusters. The structural and dynamical parameters are derived by fitting the profiles to three different models combined with mass-to-light ratios (M/L values) from population-synthesis models. The structural parameters include core radii, concentration, half-light radii, and central surface brightness. The dynamical parameters include the integrated cluster mass, integrated binding energy, central surface mass density, and predicted line of sight velocity dispersion at the cluster center. The velocity dispersions of the four clusters predicted here agree well with the observed dispersions by Larsen et al. The results here showed that the majority of the sample halo GCs are better fitted by both the King model and the Wilson model than the Sersic model. In general, the properties of the clusters in M33, M31, and the Milky Way fall in the same regions of parameter spaces. The tight correlations of cluster properties indicate a "fundamental plane" for clusters, which reflects some universal physical conditions and processes operating at the epoch of cluster formation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/3444
- Title:
- Survey of Centaurus A's Baryonic Structures II.
- Short Name:
- J/MNRAS/469/3444
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New wide-field u'g'r'i'z' Dark Energy Camera observations centred on the nearby giant elliptical galaxy NGC 5128 covering ~21 deg^2^ are used to compile a new catalogue of ~3200 globular clusters (GCs). We report 2404 newly identified candidates, including the vast majority within ~140kpc of NGC 5128. We find evidence for a transition at a galactocentric radius of R_gc_~=55kpc from GCs 'intrinsic' to NGC 5128 to those likely to have been accreted from dwarf galaxies or that may transition to the intragroup medium of the Centaurus A galaxy group. We fit power-law surface number density profiles of the form {Sigma}_N,R_gc_{prop.to}R_gc_^{Gamma}^ and find that inside the transition radius, the red GCs are more centrally concentrated than the blue, with {Gamma}_inner,red_~=-1.78 and {Gamma}_inner,blue_~=-1.40, respectively. Outside this region both profiles flatten, more dramatically for the red GCs ({Gamma}_outer,red_~=-0.33) compared to the blue ({Gamma}_outer,blue_~= -0.61), although the former is more likely to suffer contamination by background sources. The median (g'-z')_0_=1.27mag colour of the inner red population is consistent with arising from the amalgamation of two giant galaxies each less luminous than present-day NGC 5128. Both inwards and outwards of the transition radius, we find the fraction of blue GCs to dominate over the red GCs, indicating a lively history of minor mergers. Assuming the blue GCs to originate primarily in dwarf galaxies, we model the population required to explain them, while remaining consistent with NGC 5128's present-day spheroid luminosity. We find that several dozen dwarfs of luminosities L_dw,V_~= 10^6-9.3^L_V,{sun}_, following a Schechter luminosity function with a faint-end slope of -1.50<={alpha}<=-1.25 is favoured, many of which may have already been disrupted in NGC 5128's tidal field.
- ID:
- ivo://CDS.VizieR/J/AJ/150/129
- Title:
- Swift UVOT stars survey. II. RR Lyrae in M3 and M15
- Short Name:
- J/AJ/150/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of a Near-UltraViolet (NUV) survey of RR Lyrae stars from the Ultraviolet Optical Telescope (UVOT) on board the Swift Gamma-ray Burst Mission. It is well-established that RR Lyrae stars have large amplitudes in the far- and near-ultraviolet. We have used UVOT's unique wide-field NUV imaging capability to perform the first systematic NUV survey of variable stars in the Galactic globular clusters M3 and M15. We identify 280 variable stars, comprised of 275 RR Lyrae, 2 anomalous Cepheids, 1 classical Cepheid, 1 SX Phoenicis star, and 1 possible long-period or irregular variable. Only two of these are new discoveries. We compare our results to previous investigations and find excellent agreement in the periods with significantly larger amplitudes in the NUV. We map out, for the first time, an NUV Bailey diagram from globular clusters, showing the usual loci for fundamental mode RRab and first overtone RRc pulsators. We show the unique sensitivity of NUV photometry to both the temperatures and the surface gravities of RR Lyrae stars. Finally, we show evidence of an NUV period-metallicity-luminosity relationship. Future investigations will further examine the dependence of NUV pulsation parameters on metallicity and Oosterhoff classification.
- ID:
- ivo://CDS.VizieR/J/MNRAS/419/342
- Title:
- SX Phe stars in globular clusters
- Short Name:
- J/MNRAS/419/342
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study is aimed at investigating the period-luminosity relation of SX Phoenicis (SX Phe) pulsators in Galactic globular clusters (GGCs) and Local Group dwarf galaxies. We verify isochrone-fitting distances of 46 GGCs by fitting their main sequences to a carefully chosen set of nearby, unevolved subdwarfs.
- ID:
- ivo://CDS.VizieR/J/AJ/110/1186
- Title:
- SX Phe stars in NGC 5053
- Short Name:
- J/AJ/110/1186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a major search for photometrically variable blue straggler stars (BSs) in the extremely metal-poor globular cluster NGC 5053 are presented. The survey is based on photometry of over 200 CCD frames (BVI passbands) taken on 18 nights between 1985 and 1994. Five of the 16 BSs monitored for variability are identified as SX Phe stars and their photometric characteristics derived. These five stars are among the shortest-period (49<P<57min), lowest luminosity (3.0<~M_V<~3.3mag), smallest amplitude (0.08<~A_V<~0.25mag) SX Phe stars presently known. Their colors and locations in both B and V period-luminosity (P-L) diagrams suggest that four of the stars (blue stragglers 11, 13, 14, and 15 in the Nemec & Cohen 1989 catalog (1989ApJ...336..780N) are fundamental-mode pulsators, while the fifth and bluest star, No. 7, appears to be a first-overtone pulsator. One of the stars, No. 11, exhibits cycle-to-cycle light variations that are consistent with multimode pulsations; however, not enough photometric information is available to derive its secondary pulsation period. Masses for the stars, estimated directly from the general equation of stellar pulsation and relative to the RR Lyrae stars, range from 0.53M_{sun}_ (NC7) to 1.8M_{sun}_ (NC13). The SX Phe stars are used to derive improved P-L-[Fe/H] relations for SX Phe stars, from which a revised distance modulus of (m-M)0=16.06 is obtained for NGC 5053.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A9
- Title:
- Synthetic photometry as a function of redshift
- Short Name:
- J/A+A/633/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the spectral properties of proto-GCs that would host a supermassive star (SMS). Our main goal is to quantify how such a star would affect the integrated light of the cluster, and to study the detectability of such objects. We computed nonlocal thermal equilibrium atmosphere models for SMS with various combinations of stellar parameters (luminosity, effective temperature, and mass) and metallicities appropriate for GCs, and we predict their emergent spectra. Using these spectra, we calculated the total emission of young proto-GCs with SMS as predicted in a previously reported scenario, and we computed synthetic photometry in UV, optical, and near-IR bands, in particular for the James Webb Space Telescope (JWST). At an effective temperature of 10000K, the spectrum of SMSs shows a Balmer break in emission. This feature is due to strong nonlocal thermal equilibrium effects (implied by the high luminosity) and is not observed in "normal" stars. The hydrogen lines also show a peculiar behavior, with Balmer lines in emission while higher series lines are in absorption. At 7000 K, the Balmer break shows a strong absorption. At high effective temperatures, the Lyman break is found in emission. Cool and luminous SMSs are found to dominate the integrated spectrum of the cluster, except for the UV range. The predicted magnitudes of these proto-GCs are mag_AB_~28-30 between 0.7 and 8um and for redshifts z~4-10, which is detectable with the JWST. The peculiar observational features of cool SMSs imply that they might in principle be detected in color-color diagrams that probe the spectral energy distribution below and above the Balmer break.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A9
- Title:
- Synthetic spectra of galactic globular clusters
- Short Name:
- J/A+A/534/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We calculated synthetic spectra for typical chemical element mixtures (i.e., a standard alpha-enhanced distribution, and distributions displaying CN and ONa anticorrelations) found in the various subpopulations harboured by individual Galactic globular clusters. From the spectra we determined bolometric corrections to the standard Johnson-Cousins and Stroemgren filters and finally predicted colours. These bolometric corrections and colour-transformations, coupled to our theoretical isochrones with the appropriate chemical composition, provided us with a complete and self-consistent set of theoretical predictions for the effect of abundance variations on the observed cluster colour-magnitude diagrams.
