- ID:
- ivo://CDS.VizieR/J/AJ/119/1562
- Title:
- gri photometry of 48 galaxy clusters
- Short Name:
- J/AJ/119/1562
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present gri CCD photometry of 44 Abell clusters and four cluster candidates. Twenty-one clusters in our sample have spectroscopic redshifts. Fitting a relation between mean g, r, and i magnitudes and redshift for this subsample, we have calculated photometric redshifts for the remainder with an estimated accuracy of approximately 0.03. The resulting redshift range for the sample is 0.03 < z < 0.38. Color-magnitude diagrams are presented for the complete sample and used to study evolution of the galaxy population in the cluster environment.
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- 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/ApJ/812/114
- Title:
- Grism Lens-Amplified Survey from Space (GLASS). I.
- Short Name:
- J/ApJ/812/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We give an overview of the Grism Lens Amplified Survey from Space (GLASS), a large Hubble Space Telescope program aimed at obtaining grism spectroscopy of the fields of 10 massive clusters of galaxies at redshift z=0.308-0.686, including the Hubble Frontier Fields (HFF). The Wide Field Camera 3 (WFC3) yields near-infrared spectra of the cluster cores covering the wavelength range 0.81-1.69{mu}m through grisms G102 and G141, while the Advanced Camera for Surveys in parallel mode provides G800L spectra of the infall regions of the clusters. The WFC3 spectra are taken at two almost orthogonal position angles in order to minimize the effects of confusion. After summarizing the scientific drivers of GLASS, we describe the sample selection as well as the observing strategy and data processing pipeline. We then utilize MACS J0717.5+3745, a HFF cluster and the first one observed by GLASS, to illustrate the data quality and the high-level data products. Each spectrum brighter than H_AB_=23 is visually inspected by at least two co-authors and a redshift is measured when sufficient information is present in the spectra. Furthermore, we conducted a thorough search for emission lines through all of the GLASS WFC3 spectra with the aim of measuring redshifts for sources with continuum fainter than H_AB_=23. We provide a catalog of 139 emission-line-based spectroscopic redshifts for extragalactic sources, including three new redshifts of multiple image systems (one probable, two tentative).
- 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/A+A/531/A39
- Title:
- g'r'i'z'JHKs light curves of GRB 081029
- Short Name:
- J/A+A/531/A39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- GROND multi-colour follow-up of GRB 081029 is used to study the nature of the late-time extremely fast rebrightening that appears in the optical-NIR light-curve of the afterglow of GRB 081029.
- ID:
- ivo://CDS.VizieR/J/A+A/535/A57
- Title:
- g'r'i'z'JH light curves of GRB 091127
- Short Name:
- J/A+A/535/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using high-quality, broad-band afterglow data for GRB 091127, we investigate the validity of the synchrotron fireball model for gamma-ray bursts, and infer physical parameters of the ultra-relativistic outflow. We used multi-wavelength (NIR to X-ray) follow-up observations obtained with GROND simultaneously in the g'r'i'z' JH filters and the XRT onboard the Swift satellite in the 0.3 to 10keV energy range. The resulting afterglow light curve is of excellent accuracy with relative photometric errors as low as 1%, and the spectral energy distribution is well-sampled over 5 decades in energy. These data present one of the most comprehensive observing campaigns for a single GRB afterglow and allow us to test several proposed emission models and outflow characteristics in unprecedented detail.
- 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/ApJ/860/L21
- Title:
- GROND, NOT & VLT/X-shooter obs. of GRB180325A
- Short Name:
- J/ApJ/860/L21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ultraviolet (UV) extinction feature at 2175{AA} is ubiquitously observed in the Galaxy but is rarely detected at high redshifts. Here we report the spectroscopic detection of the 2175{AA} bump on the sightline to the {gamma}-ray burst (GRB) afterglow GRB180325A at z=2.2486, the only unambiguous detection over the past 10 years of GRB follow-up, at four different epochs with the Nordic Optical Telescope (NOT) and the Very Large Telescope (VLT)/X-shooter. Additional photometric observations of the afterglow are obtained with the Gamma-Ray burst Optical and Near-Infrared Detector (GROND). We construct the near-infrared to X-ray spectral energy distributions (SEDs) at four spectroscopic epochs. The SEDs are well described by a single power law and an extinction law with RV~4.4, Av~1.5, and the 2175{AA} extinction feature. The bump strength and extinction curve are shallower than the average Galactic extinction curve. We determine a metallicity of [Zn/H]{>}-0.98 from the VLT/X-shooter spectrum. We detect strong neutral carbon associated with the GRB with equivalent width of Wr({lambda}1656)=0.85+/-0.05. We also detect optical emission lines from the host galaxy. Based on the H{alpha} emission-line flux, the derived dust-corrected star formation rate is ~46+/-4M_{sun}_/yr and the predicted stellar mass is log M*/M_{sun}_~9.3+/-0.4, suggesting that the host galaxy is among the main-sequence star-forming galaxies.
- ID:
- ivo://nasa.heasarc/gwsstrpcxo
- Title:
- Groth-Westphal Strip Chandra X-Ray Point Source Catalog
- Short Name:
- GWSSTRPCXO
- Date:
- 27 Sep 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the optical and X-ray spectral properties of the sources detected in a 200-ks Chandra observation of part of the Groth-Westphal Strip (GWS) region, using the ACIS-I instrument. The authors present a relatively simple method for the detection of X-ray point sources and the calculation of limiting sensitivities, which they argue is at least as sensitive and more self-consistent than previous methods presented in the literature. A total of 158 distinct X-ray sources are included in this point-source catalogue in the ACIS-I area with a threshold Poisson detection probability of 4 x 10<sup>-6</sup>. The number counts show a relative dearth of X-ray sources in this region. A wealth of optical photometric and spectroscopic data are available in this field providing optical identifications and redshift determinations for the X-ray population. The optical photometry and spectroscopy used here are primarily from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) survey with additional redshifts obtained from the literature. These are complemented with the deeper (r ~ 26 mag) multiwaveband data (ugriz) from the Canada-France-Hawaii Telescope Legacy Survey to estimate photometric redshifts and to optically identify sources fainter than the DEEP2 magnitude limit (R<sub>AB</sub> ~ 24.5 mag). The authors focus their study on the 2 - 10 keV selected sample comprising 97 sources to the flux limit ~8 x 10<sup>-16</sup> erg/s/cm<sup>2</sup>, this being the most complete in terms of optical identification rate (86 per cent) and redshift determination fraction (63 per cent; both spectroscopic and photometric). Chandra observed the GWS, which is part of the Extended Groth Strip (EGS) region, on three separate occasions between 2002 August 11 and 22, using ACIS-I as the prime instrument. The S2 and S3 chips of the ACIS-S array were also operating during the observation, but as these are far off-axis their data are not considered further. The sequence number identifying the observations was 900144 and the three observation ID numbers (3305 on 2002-08-11, 4357 on 2002-08-12, and 4365 on 2002-08-21). This table was created by the HEASARC in July 2007 based on the merger of <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/356/568">CDS Catalog J/MNRAS/356/568</a> file table3.dat and <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/371/221">CDS Catalog J/MNRAS/371/221</a> file table2.dat. This is a service provided by NASA HEASARC .