Search

Start Over Subject galaxies
3311. Six fossil central galaxies reduced spectra
ID:
ivo://CDS.VizieR/J/A+A/553/A99
Title:
Six fossil central galaxies reduced spectra
Short Name:
J/A+A/553/A99
Date:
21 Oct 2021
Publisher:
CDS
Description:
Fossil galaxy groups are speculated to be old and highly evolved systems of galaxies that formed early in the universe and had enough time to deplete their L* galaxies through successive mergers of member galaxies, building up one massive central elliptical, but retaining the group X-ray halo. Considering that fossils are the remnants of mergers in ordinary groups, the merger history of the progenitor group is expected to be imprinted in the fossil central galaxy (FCG). We present for the first time radial gradients of single-stellar population (SSP) ages and metallicities in a sample of FCGs We took deep spectra with the long-slit spectrograph ISIS at the William Herschel Telescope (WHT) for six FCGs.
3312. Size and Structure of AGN in NGC 5548
ID:
ivo://CDS.VizieR/J/ApJ/510/659
Title:
Size and Structure of AGN in NGC 5548
Short Name:
J/ApJ/510/659
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of 3 yr of ground-based observations of the Seyfert 1 galaxy NGC 5548, which, combined with previously reported data, yield optical continuum and broad-line H{beta} light curves for a total of 8 yr. The light curves consist of over 800 points, with a typical spacing of a few days between observations. During this 8 yr period, the nuclear continuum has varied by more than a factor of 7, and the H{beta} emission line has varied by a factor of nearly 6. The H{beta} emission line responds to continuum variations with a time delay or lag of {=~}10--20 days, the precise value varying somewhat from year to year. We find some indications that the lag varies with continuum flux in the sense that the lag is larger when the source is brighter.
3313. Sizes and luminosities of stellar systems
ID:
ivo://CDS.VizieR/J/AJ/142/199
Title:
Sizes and luminosities of stellar systems
Short Name:
J/AJ/142/199
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use a combined imaging and spectroscopic survey of the nearby central cluster galaxy, M87, to assemble a sample of 34 confirmed UltraCompact Dwarfs (UCDs) with half-light radii of >=10pc measured from Hubble Space Telescope (HST) images. This doubles the existing sample in M87, making it the largest such sample for any galaxy, while extending the detection of UCDs to unprecedentedly low luminosities (MV=-9). With this expanded sample, we find no correlation between size and luminosity, in contrast to previous suggestions, and no general correlation between size and galactocentric distance. We explore the relationships between UCDs, less luminous extended clusters (including faint fuzzies), Globular Clusters (GCs), as well as early-type galaxies and their nuclei, assembling an extensive new catalog of sizes and luminosities for stellar systems. Most of the M87 UCDs follow a tight color-magnitude relation, offset from the metal-poor GCs. This, along with kinematical differences, demonstrates that most UCDs are a distinct population from normal GCs, and not simply a continuation to larger sizes and higher luminosities. The UCD color-magnitude trend couples closely with that for Virgo dwarf elliptical nuclei. We conclude that the M87 UCDs are predominantly stripped nuclei. The brightest and reddest UCDs may be the remnant nuclei of more massive galaxies while a subset of the faintest UCDs may be tidally limited and related to more compact star clusters. In the broader context of galaxy assembly, blue UCDs may trace halo build-up by accretion of low-mass satellites, while red UCDs may be markers of metal-rich bulge formation in larger galaxies.
3314. Sizes of Lyman alpha emitters at z=3.1
ID:
ivo://CDS.VizieR/J/ApJ/705/639
Title:
Sizes of Lyman alpha emitters at z=3.1
Short Name:
J/ApJ/705/639
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a rest-frame ultraviolet analysis of ~120 z~3.1 Lyman Alpha Emitters (LAEs) in the Extended Chandra Deep Field South. Using Hubble Space Telescope (HST) images taken as part of the Galaxy Evolution From Morphology and SEDS (GEMS) survey, Great Observatories Origins Deep Survey (GOODS), and Hubble Ultradeep Field surveys, we analyze the sizes of LAEs, as well as the spatial distribution of their components, which are defined as distinct clumps of UV-continuum emission. We set an upper limit of ~1kpc (~0.1") on the rms offset between the centroids of the continuum and Ly{alpha} emission. Most of the multi-component LAEs identified in shallow frames become connected in deeper images, suggesting that the majority of the rest-UV "clumps" are individual star-forming regions within a single system.
3315. SLACS. XIII. Galaxy-scale strong lens candidates
ID:
ivo://CDS.VizieR/J/ApJ/851/48
Title:
SLACS. XIII. Galaxy-scale strong lens candidates
Short Name:
J/ApJ/851/48
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the full sample of 118 galaxy-scale strong-lens candidates in the Sloan Lens ACS (SLACS) Survey for the Masses (S4TM) Survey, which are spectroscopically selected from the final data release of the Sloan Digital Sky Survey. Follow-up Hubble Space Telescope (HST) imaging observations confirm that 40 candidates are definite strong lenses with multiple lensed images. The foreground-lens galaxies are found to be early-type galaxies (ETGs) at redshifts 0.06-0.44, and background sources are emission-line galaxies at redshifts 0.22-1.29. As an extension of the SLACS Survey, the S4TM Survey is the first attempt to preferentially search for strong-lens systems with relatively lower lens masses than those in the pre-existing strong-lens samples. By fitting HST data with a singular isothermal ellipsoid model, we find that the total projected mass within the Einstein radius of the S4TM strong-lens sample ranges from 3x10^10^M_{sun}_ to 2x10^11^M_{sun}_. In Shu+ (2015ApJ...803...71S), we have derived the total stellar mass of the S4TM lenses to be 5x10^10^M_{sun}_ to 1x10^12^M_{sun}_. Both the total enclosed mass and stellar mass of the S4TM lenses are on average almost a factor of 2 smaller than those of the SLACS lenses, which also represent the typical mass scales of the current strong-lens samples. The extended mass coverage provided by the S4TM sample can enable a direct test, with the aid of strong lensing, for transitions in scaling relations, kinematic properties, mass structure, and dark-matter content trends of ETGs at intermediate-mass scales as noted in previous studies.
3316. SL2S galaxy-scale lens sample. III.
ID:
ivo://CDS.VizieR/J/ApJ/777/97
Title:
SL2S galaxy-scale lens sample. III.
Short Name:
J/ApJ/777/97
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Hubble Space Telescope (HST) imaging data and Canada-France-Hawaii Telescope (CFHT) near-infrared ground-based images for the final sample of 56 candidate galaxy-scale lenses uncovered in the CFHT Legacy Survey as part of the Strong Lensing in the Legacy Survey (SL2S) project. The new images are used to perform lens modeling, measure surface photometry, and estimate stellar masses of the deflector early-type galaxies (ETGs). Lens modeling is performed on the HST images (or CFHT when HST is not available) by fitting the spatially extended light distribution of the lensed features assuming a singular isothermal ellipsoid mass profile and by reconstructing the intrinsic source light distribution on a pixelized grid. Based on the analysis of systematic uncertainties and comparison with inference based on different methods, we estimate that our Einstein radii are accurate to ~3%. HST imaging provides a much higher success rate in confirming gravitational lenses and measuring their Einstein radii than CFHT imaging does. Lens modeling with ground-based images, however, when successful, yields Einstein radius measurements that are competitive with space-based images. Information from the lens models is used together with spectroscopic information from companion Paper IV (2013ApJ...777...98S) to classify the systems, resulting in a final sample of 39 confirmed (grade A) lenses and 17 promising candidates (grade B,C).
3317. SL2S galaxy-scale sample of lens candidates
ID:
ivo://CDS.VizieR/J/ApJ/785/144
Title:
SL2S galaxy-scale sample of lens candidates
Short Name:
J/ApJ/785/144
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present RINGFINDER, a tool for finding galaxy-scale strong gravitational lenses in multi-band imaging data. By construction, the method is sensitive to configurations involving a massive foreground ETG and a faint, background, blue source. RINGFINDER detects the presence of blue residuals embedded in an otherwise smooth red light distribution by difference imaging in two bands. The method is automated for efficient application to current and future surveys, having originally been designed for the 150 deg^2^ Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). We describe each of the steps of RINGFINDER. We then carry out extensive simulations to assess completeness and purity. For sources with magnification {mu}>4, RINGFINDER reaches 42% (25%) completeness and 29% (86%) purity before (after) visual inspection. The completeness of RINGFINDER is substantially improved in the particular range of Einstein radii 0.8"<=R_Ein_<=2.0" and lensed images brighter than g=22.5, where it can be as high as ~70%. RINGFINDER does not introduce any significant bias in the source or deflector population. We conclude by presenting the final catalog of RINGFINDER CFHTLS galaxy-scale strong lens candidates. Additional information obtained with Hubble Space Telescope and Keck adaptive optics high-resolution imaging, and with Keck and Very Large Telescope spectroscopy, is used to assess the validity of our classification and measure the redshift of the foreground and the background objects. From an initial sample of 640000 ETGs, RINGFINDER returns 2500 candidates, which we further reduce by visual inspection to 330 candidates. We confirm 33 new gravitational lenses from the main sample of candidates, plus an additional 16 systems taken from earlier versions of RINGFINDER. First applications are presented in the Strong Lensing Legacy Survey galaxy-scale lens sample paper series.
3318. Slug analysis of star clusters in NGC 628 & 7793
ID:
ivo://CDS.VizieR/J/ApJ/812/147
Title:
Slug analysis of star clusters in NGC 628 & 7793
Short Name:
J/ApJ/812/147
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate a novel Bayesian analysis method, based on the Stochastically Lighting Up Galaxies (slug) code, to derive the masses, ages, and extinctions of star clusters from integrated light photometry. Unlike many analysis methods, slug correctly accounts for incomplete initial mass function (IMF) sampling, and returns full posterior probability distributions rather than simply probability maxima. We apply our technique to 621 visually confirmed clusters in two nearby galaxies, NGC 628 and NGC 7793, that are part of the Legacy Extragalactic UV Survey (LEGUS). LEGUS provides Hubble Space Telescope photometry in the NUV, U, B, V, and I bands. We analyze the sensitivity of the derived cluster properties to choices of prior probability distribution, evolutionary tracks, IMF, metallicity, treatment of nebular emission, and extinction curve. We find that slug's results for individual clusters are insensitive to most of these choices, but that the posterior probability distributions we derive are often quite broad, and sometimes multi-peaked and quite sensitive to the choice of priors. In contrast, the properties of the cluster population as a whole are relatively robust against all of these choices. We also compare our results from slug to those derived with a conventional non-stochastic fitting code, Yggdrasil. We show that slug's stochastic models are generally a better fit to the observations than the deterministic ones used by Yggdrasil. However, the overall properties of the cluster populations recovered by both codes are qualitatively similar.
3319. SLUGGS globular clusters in early-type galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/428/389
Title:
SLUGGS globular clusters in early-type galaxies
Short Name:
J/MNRAS/428/389
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a spectrophotometric survey of 2522 extragalactic globular clusters (GCs) around 12 early-type galaxies, nine of which have not been published previously. Combining space-based and multicolour wide-field ground-based imaging, with spectra from the Keck/DEep Imaging Multi-Object Spectrograph (DEIMOS) instrument, we obtain an average of 160 GC radial velocities per galaxy, with a high-velocity precision of ~15km/s per GC. After studying the photometric properties of the GC systems, such as their spatial and colour distributions, we focus on the kinematics of metal-poor (blue) and metal-rich (red) GC subpopulations to an average distance of ~8 effective radii from the galaxy centre.
3320. SLUGGS NGC 3607 and 3608 globular clusters
ID:
ivo://CDS.VizieR/J/MNRAS/458/105
Title:
SLUGGS NGC 3607 and 3608 globular clusters
Short Name:
J/MNRAS/458/105
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an investigation of the globular cluster (GC) systems of NGC 3607 and NGC 3608 as part of the ongoing SLUGGS (SAGES Legacy Unifying Globulars and GalaxieS) survey. We use wide-field imaging data from the Subaru telescope in the g, r and i filters to analyse the radial density, colour and azimuthal distributions of both GC systems. With the complementary kinematic data obtained from the Keck II telescope, we measure the radial velocities of a total of 81 GCs. Our results show that the GC systems of NGC 3607 and NGC 3608 have a detectable spatial extent of ~15 and 13 galaxy effective radii, respectively. Both GC systems show a clear bimodal colour distribution. We detect a significant radial colour gradient for the GC subpopulations in both galaxies. NGC 3607 exhibits an overabundance of red GCs on the galaxy minor axis and NGC 3608 shows a misalignment in the GC subpopulation position angles with respect to the galaxy stellar component. With the aid of literature data, we discuss several relationships between the properties of GC systems and their host galaxies. A one-to-one relation between the ellipticities of red GCs and the galaxy stellar light emphasizes the evolutionary similarities between them. In our sample of four slowly rotating galaxies with kinematically decoupled cores, we observe a higher ellipticity for the blue GC subpopulation than their red counterparts. Also, we notice the flattening of negative colour gradients for the blue GC subpopulations with increasing galaxy stellar mass. Finally, we discuss the formation scenarios associated with the blue GC subpopulation.

Limit your search

more »

more »

more »

more »

  • 24,327
  • 11