- ID:
- ivo://CDS.VizieR/J/AJ/127/2674
- Title:
- Globular clusters in Sculptor group
- Short Name:
- J/AJ/127/2674
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use CTIO 4m Mosaic II images taken with the Washington CM and Harris R filters to identify candidate globular clusters in the six major galaxies of the Sculptor group: NGC 45, 55, 247, 254, 300, and 7793. From follow-up spectroscopy with Hydra-CTIO, we find 19 new globular clusters in NGC 55, 247, 253, and 300, bringing the total number of known Sculptor group globular clusters to 36. The newly discovered clusters have spectroscopic ages consistent with those of old Milky Way globular clusters, and the majority are metal-poor.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/559/812
- Title:
- Globular cluster system in M87
- Short Name:
- J/ApJ/559/812
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive database of kinematic, photometric, and positional information for 352 objects in the field of M87 (NGC 4486), the central giant elliptical galaxy in the Virgo Cluster; the majority of the tracers are globular clusters associated with that galaxy. New kinematic information comes from multislit observations with the Multi-Object Spectrograph (MOS) of the Canada-France-Hawaii Telescope (CFHT), an investigation that has added 96 new velocities to and confirmed many of the earlier values in a preexisting data set of 256 velocities published elsewhere. The photometry, consisting of magnitudes and colors in the Washington (T_1_, C-T_1_) system, is based on CCD observations made at the Cerro Tololo Inter-American Observatory (CTIO) and the Kitt Peak National Observatory (KPNO).
- ID:
- ivo://CDS.VizieR/J/ApJ/675/1233
- Title:
- gri photometry in M37 (NGC 2099)
- Short Name:
- J/ApJ/675/1233
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a deep (15~<r~<23 ), 20 night survey for transiting planets in the intermediate-age open cluster M37 (NGC 2099) using the Megacam wide-field mosaic CCD camera on the 6.5m MMT. In this paper we describe the observations and data reduction procedures for the survey and analyze the stellar content and dynamical state of the cluster. By combining high-resolution spectroscopy with existing BVI_C_K_s and new gri color-magnitude diagrams, we determine the fundamental cluster parameters: t=485+/-28Myr, without overshooting (t=550+/-30Myr, with overshooting), E(B-V)=0.227+/-0.038, (m-M)_V_=11.57+/-0.13, and [M/H]=+0.045+/-0.044, which are in good agreement with, although more precise than, previous measurements. We determine the mass function down to 0.3M_{sun}_ and use this to estimate the total cluster mass of 3640+/-170M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/ApJ/857/132
- Title:
- gri photometry of NGC 796 cluster
- Short Name:
- J/ApJ/857/132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 796 is a massive young cluster located 59kpc from us in the diffuse intergalactic medium of the 1/5-1/10Z_{sun}_ Magellanic Bridge, allowing us to probe variations in star formation and stellar evolution processes as a function of metallicity in a resolved fashion, and providing a link between resolved studies of nearby solar-metallicity and unresolved distant metal-poor clusters located in high-redshift galaxies. In this paper, we present adaptive optics griH{alpha} imaging of NGC 796 (at 0.5", which is ~0.14pc at the cluster distance) along with optical spectroscopy of two bright members to quantify the cluster properties. Our aim is to explore whether star formation and stellar evolution vary as a function of metallicity by comparing the properties of NGC 796 to higher-metallicity clusters. We find an age of 20_-5_^+12^Myr from isochronal fitting of the cluster main sequence in the color-magnitude diagram. Based on the cluster luminosity function, we derive a top-heavy stellar initial mass function (IMF) with a slope {alpha}=1.99+/-0.2, hinting at a metallicity and/or environmental dependence of the IMF, which may lead to a top-heavy IMF in the early universe. Study of the H{alpha} emission-line stars reveals that classical Be stars constitute a higher fraction of the total B-type stars when compared with similar clusters at greater metallicity, providing some support to the chemically homogeneous theory of stellar evolution. Overall, NGC 796 has a total estimated mass of 990+/-200M_{sun}_, and a core radius of 1.4+/-0.3pc, which classifies it as a massive young open cluster, unique in the diffuse interstellar medium of the Magellanic Bridge.
- ID:
- ivo://CDS.VizieR/J/AJ/149/183
- Title:
- gri photometry of variables in NGC 4258
- Short Name:
- J/AJ/149/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a ground-based survey for Cepheid variables in NGC4258. This galaxy plays a key role in the Extragalactic Distance Scale due to its very precise and accurate distance determination via very long baseline interferometry observations of water masers. We imaged two fields within this galaxy using the Gemini North telescope and the Gemini Multi-Object Spectrograph, obtaining 16 epochs of data in the Sloan Digital Sky Survey gri bands over 4yr. We carried out point-spread function photometry and detected 94 Cepheids with periods between 7 and 127 days, as well as an additional 215 variables which may be Cepheids or Population II pulsators. We used the Cepheid sample to test the absolute calibration of theoretical gri Period-Luminosity relations and found good agreement with the maser distance to this galaxy. The expected data products from the Large Synoptic Survey Telescope should enable Cepheid searches out to at least 10Mpc.
- ID:
- ivo://CDS.VizieR/J/MNRAS/431/1405
- Title:
- griz and CT1 photometry in M87
- Short Name:
- J/MNRAS/431/1405
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Gemini griz' photometry for 521 globular cluster (GC) candidates in a 5.5x5.5arcmin^2^ field centred 3.8-arcmin to the south and 0.9-arcmin to the west of the centre of the giant elliptical galaxy NGC 4486. All these objects have previously published (C-T1) photometry. We also present new (C-T1) photometry for 338 globulars, within 1.7-arcmin in galactocentric radius, which have (g-z) colours in the photometric system adopted by the Virgo Cluster Survey of the Advanced Camera for Surveys of the Hubble Space Telescope (HST). These photometric data are used to define a self-consistent multicolour grid (avoiding polynomial fits) and preliminarily calibrated in terms of two chemical abundance scales. The resulting multicolour colour-chemical abundance relations are used to test GC chemical abundance distributions. This is accomplished by modelling the 10 GC colour histograms that can be defined in terms of the Cgriz' bands. Our results suggest that the best fit to the GC observed colour histograms is consistent with a genuinely bimodal chemical abundance distribution N_GC_(Z). On the other side, each ('blue' and 'red') GC subpopulation follows a distinct colour-colour relation.
- ID:
- ivo://CDS.VizieR/J/ApJ/862/123
- Title:
- griz light curves of 15 DES quasars
- Short Name:
- J/ApJ/862/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present accretion disk size measurements for 15 luminous quasars at 0.7<=z<=1.9 derived from griz light curves from the Dark Energy Survey. We measure the disk sizes with continuum reverberation mapping using two methods, both of which are derived from the expectation that accretion disks have a radial temperature gradient and the continuum emission at a given radius is well described by a single blackbody. In the first method we measure the relative lags between the multiband light curves, which provides the relative time lag between shorter and longer wavelength variations. From this, we are only able to constrain upper limits on disk sizes, as many are consistent with no lag the 2{sigma} level. The second method fits the model parameters for the canonical thin disk directly rather than solving for the individual time lags between the light curves. Our measurements demonstrate good agreement with the sizes predicted by this model for accretion rates between 0.3 and 1 times the Eddington rate. Given our large uncertainties, our measurements are also consistent with disk size measurements from gravitational microlensing studies of strongly lensed quasars, as well as other photometric reverberation mapping results, that find disk sizes that are a factor of a few (~3) larger than predictions.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A44
- Title:
- gr photometry of Sextans A and Sextans B
- Short Name:
- J/A+A/566/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed study of the stellar and HI structure of the dwarf irregular galaxies Sextans A and Sextans B, members of the NGC3109 association. We use newly obtained deep (r~26.5) and wide field g,r photometry to extend the Surface Brightness (SB) profiles of the two galaxies down to mu_V_~31.0mag/arcsec^2^. We find that both galaxies are significantly more extended than what previously traced with surface photometry, out to ~4kpc from their centers along their major axis. Older stars are found to have more extended distribution with respect to younger populations. We obtain the first estimate of the mean metallicity for the old stars in Sex B, from the color distribution of the Red Giant Branch, <[Fe/H]>=-1.6. The SB profiles show significant changes of slope and cannot be fitted with a single Sersic model. Both galaxies have HI discs as massive as their respective stellar components. In both cases the HI discs display solid-body rotation with maximum amplitude of ~50km/s (albeit with significant uncertainty due to the poorly constrained inclination), implying a dynamical mass ~10^9^~M_{sun}_, a mass-to-light ratio M/L_V_~25 and a dark to-barionic mass ratio of ~10. The distribution of the stellar components is more extended than the gaseous disc in both galaxies. We find that the main, approximately round-shaped, stellar body of Sex A is surrounded by an elongated low-SB stellar halo that can be interpreted as a tidal tail, similar to that found in another member of the same association (Antlia). We discuss these, as well as other evidences of tidal disturbance, in the framework of a past passage of the NGC3109 association close to the Milky Way, that has been hypothesized by several authors and is also supported by the recently discovered filamentary configuration of the association itself
- ID:
- ivo://CDS.VizieR/J/ApJ/803/63
- Title:
- gr photometry of stars in Kim 2
- Short Name:
- J/ApJ/803/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a new, low-luminosity star cluster in the outer halo of the Milky Way. High-quality gr photometry is presented, from which a color-magnitude diagram is constructed, and estimates of age, [Fe/H], [{alpha}/Fe], and distance are derived. The star cluster, which we designate as Kim 2, lies at a heliocentric distance of ~105kpc. With a half-light radius of ~12.8pc and ellipticity of {epsilon}~0.12, it shares the properties of outer halo globular clusters, except for at higher metallicity ([Fe/H]~-1.0) and lower luminosity (M_v_~-1.5). These parameters are similar to those for the globular cluster AM 4, which is considered to be associated with the Sagittarius dwarf spheroidal galaxy. We find evidence of dynamical mass segregation and the presence of extra-tidal stars that suggests that Kim 2 is most likely a star cluster. Spectroscopic observations for radial-velocity membership and chemical abundance measurements are needed to further understand the nature of the object.
- ID:
- ivo://CDS.VizieR/II/143A
- Title:
- Guide Star Photometric Catalog, Updated Version 1
- Short Name:
- II/143A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Guide Star Photometric Catalog (GSPC) is an all-sky set of 1477 photoelectrically determined BV sequences covering the magnitude range from 9 to 15. The GSPC was created to provide photometric calibrators for the HST Guide Star Catalog (GSC). Each sequence nominally contains (at least) six stars, each with a photometric precision of 0.05 mag. In practice, a small number of sequences contain fewer stars; and the precisions achieved for the faintest stars are more nearly 0.1 mag. For declinations greater than +3 degrees the sequences generally lie near the centers of the original Palomar Observatory - National Geographic Society Sky Atlas. Other sequences lie near the centers of the ESO/SERC Southern Sky Atlas. The catalog also includes a list of suspected variable stars, a bibliography of literature sequences, and additional information which was useful in the data reduction and for quality control of the final catalog. The full catalog is made of 7 FITS files: tables 1 to 5, references (table 6 of the paper) and the actual catalogue (table 7 of the paper). The ascii versions of Tables 1 to 5 are included in this file; the ascii version of the references (refs.dat) and of the actual catalogue (catalog.dat) are described here. The updated version 1 was created by replacing photometric sequences P040, P421, S335 and S742 in GSPC version 1. The updated sequences have improved photometry and/or positions. In addition the sigma's in V and B-V (here e_V and e_B-V) were replaced with the values provided by the authors when we noted a discrepancy with the published values.
