The SLUGGS Survey: A Catalog of Over 4000 Globular Cluster Radial Velocities in 27 Nearby Early-type Galaxies (original) (raw)
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The SLUGGS Survey: kinematics for over 2500 globular clusters in 12 early-type galaxies
Monthly Notices of the Royal Astronomical Society, 2013
We present a spectro-photometric survey of 2522 extragalactic globular clusters (GCs) around twelve early-type galaxies, nine of which have not been published previously. Combining space-based and multi-colour wide field ground-based imaging, with spectra from the Keck DEIMOS instrument, we obtain an average of 160 GC radial velocities per galaxy, with a high velocity precision of ∼ 15 km s −1 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.
THE SLUGGS SURVEY: WIDE-FIELD STELLAR KINEMATICS OF EARLY-TYPE GALAXIES
The Astrophysical Journal, 2014
We present stellar kinematics of 22 nearby early-type galaxies (ETGs), based on two-dimensional (2D) absorption line stellar spectroscopy out to ∼ 2-4 R e (effective radii), as part of the ongoing SLUGGS survey. The galaxies span a factor of 20 in intrinsic luminosity, as well as a full range of environment and ETG morphology. Our data consist of good velocity resolution (σ inst ∼ 25 km s −1 ) integrated stellar-light spectra extracted from the individual slitlets of custom made Keck/DEIMOS slitmasks. We extract stellar kinematics measurements (V , σ, h 3 , and h 4 ) for each galaxy. Combining with literature values from smaller radii we present 2D spatially resolved maps of the large-scale kinematic structure in each galaxy. We find that the kinematic homogeneity found inside 1 R e often breaks down at larger radii, where a variety of kinematic behaviors are observed. While central slow rotators remain slowly rotating in their halos, central fast rotators show more diversity, ranging from rapidly increasing to rapidly declining specific angular momentum profiles in the outer regions. There are indications that the outer trends depend on morphological type, and we suggest that the apparent unification of the elliptical and lenticular (S0) galaxy families in the ATLAS 3D survey may be a consequence of a limited field of view. Several galaxies in our sample show multiple lines of evidence for distinct disk components embedded in more slowly rotating spheroids, and we suggest a joint photometric-kinematic approach for robust bulge-disk decomposition. Our observational results appear generally consistent with a picture of two-phase (in-situ plus accretion) galaxy formation.
The Astrophysical Journal, 2014
We introduce and provide the scientific motivation for a wide-field photometric and spectroscopic chemodynamical survey of nearby early-type galaxies (ETGs) and their globular cluster (GC) systems. The SLUGGS a (SAGES Legacy Unifying Globulars and GalaxieS) survey is being carried out primarily with Subaru/Suprime-Cam and Keck/DEIMOS. The former provides deep gri imaging over a 900 arcmin 2 field-of-view to characterize GC and host galaxy colors and spatial distributions, and to identify spectroscopic targets. The NIR Ca II triplet provides GC line-of-sight velocities and metallicities out to typically ∼ 8 R e , and to ∼ 15 R e in some cases. New techniques to extract integrated stellar kinematics and metallicities to large radii (∼ 2-3 R e ) are used in concert with GC data to create two-dimensional velocity and metallicity maps for comparison with simulations of galaxy formation. The advantages of SLUGGS compared with other, complementary, 2D-chemodynamical surveys are its superior velocity resolution, radial extent, and multiple halo tracers. We describe the sample of 25 nearby ETGs, the selection criteria for galaxies and GCs, the observing strategies, the data reduction techniques, and modeling methods. The survey observations are nearly complete and more than 30 papers have so far been published using SLUGGS data. Here we summarize some initial results, including signatures of two-phase galaxy assembly, evidence for GC metallicity bimodality, and a novel framework for the formation of extended star clusters and ultracompact dwarfs. An integrated overview of current chemodynamical constraints on GC systems points to separate, in-situ formation modes at high redshifts for metal-poor and metal-rich GCs.
High‐Precision Stellar Radial Velocities in the Galactic Center
The Astrophysical Journal, 2003
We present radial velocities for 85 cool stars projected onto the central parsec of the Galaxy. The majority of these velocities have relative errors of 1kmsAˋ1,orafactorof1 km s À1 , or a factor of 1kmsAˋ1,orafactorof30-100 smaller than those previously obtained with proper-motion or other radial velocity measurements for a similar stellar sample. The error in a typical individual stellar velocity, including all sources of uncertainty, is 1.7 km s À1 . Two similar data sets were obtained 1 month apart, and the total error in the relative velocities is 0.80 km s À1 in the case where an object is common to both data sets. The data are used to characterize the velocity distribution of the old population in the Galactic center. We find that the stars have a Gaussian velocity distribution with a mean heliocentric velocity of À10:1 AE 11:0 km s À1 (blueshifted) and a standard deviation of 100:9 AE 7:7 km s À1 ; the mean velocity of the sample is consistent with no bulk line-of-sight motion with respect to the local standard of rest. At the 1 level, the data are consistent with a symmetric velocity distribution about any arbitrary axis in the plane of the sky. We find evidence for a flattening in the distribution of late-type stars within a radius of $0.4 pc and infer a volume density distribution of r À1/4 in this region. Finally, we establish a first epoch of radial velocity measurements that can be compared with subsequent epochs to measure small accelerations (1 km s À1 yr À1 ), corresponding to the magnitude expected over a time span of several years for stars nearest to Sgr A*.
Space Velocities of Southern Globular Clusters. IV. First Results for Inner-Galaxy Clusters
Astronomical Journal, 2002
We discuss the kinematics of these clusters and of three additional bulge clusters -- NGC 6522, NGC 6528 and NFC 6553 -- whose proper motions with respect to bulge stars had been determined previously. We find that all of the clusters have velocities that confine them to the bulge region. Of the three metal poor clusters ([Fe/H] < -1.0), NGC 6522, and NGC 6723 have kinematics consistent with halo membership. The third cluster, NGC 6266 however, appears to belong to a rotationally-supported system. Of the four metal rich clusters ([Fe/H] >= -1.0), NGC 6304 and NGC 6553 also have kinematics consistent with membership to a rotationally-supported system. NGC 6528 has kinematics, metallicity and mass that argue in favor of a genuine Milky-Way bar cluster. NGC 6316's kinematics indicate membership to a hotter system than the bar.
Using a dynamical 3-D reconstruction procedure we estimate the peculiar velocities of R 0 Abell/ACO galaxy clusters from their measured redshift within 25000 km/sec. The reconstruction algorithm relies on the linear gravitational instability hypothesis, assumes linear biasing and requires an input value of the cluster-parameter (c 0:6 =b c), which we estimated in Branchini & Plionis (1995) to be c ' 0:21. The resulting cluster velocity eld is dominated by a large scale streaming motion along the Perseus Pisces{Great Attractor base-line directed towards the Shapley concentration, in qualitative agreement with the galaxy velocity eld on smaller scales. Fitting the predicted cluster peculiar velocities to a dipole term, in the local group frame and within a distance of 18000 km/sec, we recover extremely well both the local group velocity and direction, in disagreement with the Lauer & Postman (1994) observation. However, we nd a 6% probability that their observed velocity eld could be a realization of our corresponding one, if the latter is convolved with their large distance dependent errors. Our predicted cluster bulk velocity amplitude agrees well with that deduced by the POTENT and the da Costa et al. (1995) analyses of observed galaxy motions at 5000 6000 km/sec; it decreases thereafter while at the Lauer & Postman limiting depth (15000 km/sec) its amplitude is 150 km/sec, in comfortable agreement with most cosmological models.
Space velocities of southern globular clusters. I. Astrometric techniques and first results
The Astronomical Journal, 1997
We have measured the absolute proper motions of globular clusters NGC 2808, 3201, 4372, 4833, 5927 and 5986. The proper motions are on the Hipparcos system, and they are the first determinations ever made for these low Galactic latitude clusters. The proper motion uncertainties range from 0.3 to 0.5 mas yr −1 . The inferred orbits indicate that 1) the single metal rich cluster in our sample, NGC 5927, dynamically belongs to the thick disk, 2) the remaining metal poor clusters have rather low-energy orbits of high eccentricity; among these, there appear to be two "pairs" of dynamically associated clusters, 3) the most energetic cluster in our sample, NGC 3201 is on a highly retrograde orbitwhich had already been surmised from radial velocity alone -with an apocentric distance of 22 kpc, and 4) none of the metal poor clusters appear to be associated with the recently detected SDSS streams, or with the Monoceros structure.
Radial kinematics of brightest cluster galaxies
Monthly Notices of The Royal Astronomical Society, 2008
This is the first of a series of papers devoted to the investigation of a large sample of brightest cluster galaxies (BCGs), their kinematic and stellar population properties, and the relationships between those and the properties of the cluster. We have obtained high signal-to-noise ratio, long-slit spectra of these galaxies with Gemini and WHT with the primary purpose of investigating their stellar population properties. This paper describes the selection methods and criteria used to compile a new sample of galaxies, concentrating on BCGs previously classified as containing a halo (cD galaxies), together with the observations and data reduction. Here, we present the full sample of galaxies, and the measurement and interpretation of the radial velocity and velocity dispersion profiles of 41 BCGs. We find clear rotation curves for a number of these giant galaxies. In particular, we find rapid rotation (> 100 km s −1 ) for two BCGs, NGC6034 and NGC7768, indicating that it is unlikely that they formed through dissipationless mergers. Velocity substructure in the form of kinematically decoupled cores is detected in 12 galaxies, and we find five galaxies with velocity dispersion increasing with radius. The amount of rotation, the velocity substructure and the position of BCGs on the anisotropy-luminosity diagram are very similar to those of "ordinary" giant ellipticals in high density environments.
The Dynamics of Globular Clusters and Elliptical Galaxies
arXiv (Cornell University), 2020
Equations of motion are generated for an idealised model spherical galaxy or globular cluster evolving from the epoch of galactic separation until it attains a semi-equilibrium state through gravitational collapse. The theoretical radial surface density is computed and compared with two globular clusters, M15 and M80, and shows a good fit to observational data. The model is contrasted with King's model, and mean cycle time and velocity are computed. The velocity-radius curve is developed, and Gaussian RMS values derived from which half-light radius vs. mass are plotted for 735 spherical objects, including 544 normal ellipticals and compact, massive, and intermediate mass objects. These latter show a linear mean log-log R − M vir slope of 0.604 ± 0.003, equivalent to a Faber-Jackson slope of γ = 3.66±0.009 over a mass range of 7 decades. and a slope of 0.0045 ± 0.0001 on a semi-log plot of R 1/2 − σ. Globular clusters, dwarf elliptical and dwarf spherical galaxies show a distinct anomaly on these plots, consistent with the ellipticals containing a supermassive black hole (SMBH) whose mass increases as the velocity dispersion increases, compared with the remaining types of spherical or irregular galaxies without a massive core.
A MEASUREMENT OF LARGE-SCALE PECULIAR VELOCITIES OF CLUSTERS OF GALAXIES: TECHNICAL DETAILS
The Astrophysical Journal, 2009
Peculiar velocities of clusters of galaxies can be measured by studying the fluctuations in the cosmic microwave background (CMB) generated by the scattering of the microwave photons by the hot X-ray-emitting gas inside clusters. While for individual clusters such measurements result in large errors, a large statistical sample of clusters allows one to study cumulative quantities dominated by the overall bulk flow of the sample with the statistical errors integrating down. We present results from such a measurement using the largest all-sky X-ray cluster catalog combined to date and the 3 yr WMAP CMB data. We find a strong and coherent bulk flow on scales out to at least տ300