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Full-Text Articles in Astrophysics and Astronomy
The Supermassive Black Hole And Double Nucleus Of The Core Elliptical Ngc 5419, Ximena Mazzalay, Jens Thomas, Roberto P. Saglia, Gary A. Wegner
The Supermassive Black Hole And Double Nucleus Of The Core Elliptical Ngc 5419, Ximena Mazzalay, Jens Thomas, Roberto P. Saglia, Gary A. Wegner
Dartmouth Scholarship
We obtained adaptive-optics assisted SINFONI observations of the central regions of the giant elliptical galaxy NGC5419 with a spatial resolution of 0.2 arcsec (≈55 pc). NGC5419 has a large depleted stellar core with a radius of 1.58 arcsec (430 pc). HST and SINFONI images show a point source located at the galaxy's photocentre, which is likely associated with the low-luminosity AGN previously detected in NGC5419. Both the HST and SINFONI images also show a second nucleus, off-centred by 0.25 arcsec (≈70 pc). Outside of the central double nucleus, we measure an almost constant velocity dispersion of σ∼350 km/s. In the …
Peering Through The Dust: Nustar Observations Of Two First-2mass Red Quasars, Stephanie M. Lamassa, Angelo Ricarte, Eilat Glikman, C. Megan Urry, Daniel Stern, Tahir Yaqoob, George B. Lansbury, Francesca Civano
Peering Through The Dust: Nustar Observations Of Two First-2mass Red Quasars, Stephanie M. Lamassa, Angelo Ricarte, Eilat Glikman, C. Megan Urry, Daniel Stern, Tahir Yaqoob, George B. Lansbury, Francesca Civano
Dartmouth Scholarship
Some reddened quasars appear to be transitional objects in the merger-induced black hole growth/galaxy evolution paradigm, where a heavily obscured nucleus starts to be unveiled by powerful quasar winds evacuating the surrounding cocoon of dust and gas. Hard X-ray observations are able to peer through this gas and dust, revealing the properties of circumnuclear obscuration. Here, we present NuSTAR and XMM-Newton/Chandra observations of FIRST-2MASS selected red quasars F2M 0830+3759 and F2M 1227+3214. We find that though F2M 0830+3759 is moderately obscured (NH,Z=2.1±0.2×1022 cm−2) and F2M 1227+3214 is mildly absorbed (NH,Z=3.4+0.8−0.7×1021 cm−2 …
The Nustar Extragalactic Surveys: Overview And Catalog From The Cosmos Field, F. Civano, R. C. Hickox, S. Puccetti, A. Comastri
The Nustar Extragalactic Surveys: Overview And Catalog From The Cosmos Field, F. Civano, R. C. Hickox, S. Puccetti, A. Comastri
Dartmouth Scholarship
To provide the census of the sources contributing to the X-ray background peak above 10 keV, NuSTAR is performing extragalactic surveys using a three-tier "wedding cake" approach. We present the NuSTAR survey of the COSMOS field, the medium sensitivity and medium area tier, covering 1.7 deg2 and overlapping with both Chandra and XMM-Newton data. This survey consists of 121 observations for a total exposure of ~3 Ms. To fully exploit these data, we developed a new detection strategy, carefully tested through extensive simulations. The survey sensitivity at 20% completeness is 5.9, 2.9 and 6.4 x 10^-14 erg/cm2/s in the 3-24 …
Star Formation And Relaxation In 379 Nearby Galaxy Clusters, Seth A. Cohen, Ryan C. Hickox, Gary A. Wegner
Star Formation And Relaxation In 379 Nearby Galaxy Clusters, Seth A. Cohen, Ryan C. Hickox, Gary A. Wegner
Dartmouth Scholarship
We investigate the relationship between star formation (SF) and level of relaxation in a sample of 379 galaxy clusters at z < 0.2. We use data from the Sloan Digital Sky Survey to measure cluster membership and level of relaxation, and to select star-forming galaxies based on mid-infrared emission detected with the Wide-Field Infrared Survey Explorer. For galaxies with absolute magnitudes Mr < −19.5, we find an inverse correlation between SF fraction and cluster relaxation: as a cluster becomes less relaxed, its SF fraction increases. Furthermore, in general, the subtracted SF fraction in all unrelaxed clusters (0.117 ± 0.003) is higher than that in all relaxed clusters (0.097 ± 0.005). We verify the validity of our SF calculation methods and membership criteria through analysis of previous work. Our results agree with previous findings that a weak correlation exists between cluster SF and dynamical state, possibly because unrelaxed clusters are less evolved relative to relaxed clusters.
The Double Galaxy Cluster Abell 2465 – Ii. Star Formation In The Cluster, Gary A. Wegner, Devin S. Chu, Ho Seong Hwang
The Double Galaxy Cluster Abell 2465 – Ii. Star Formation In The Cluster, Gary A. Wegner, Devin S. Chu, Ho Seong Hwang
Dartmouth Scholarship
We investigate the star formation rate and its location in the major merger cluster Abell 2465 at z = 0.245. Optical properties of the cluster are described in Paper I. Measurements of the Hα and infrared dust emission of galaxies in the cluster were made with an interference filter centred on the redshifted line at a wavelength of 817 nm and utilized data from the WISE satellite 12 μm band. Imaging in the Johnson U and B bands was obtained, and along with SDSS u and r was used to study the blue fraction, which appears enhanced, as a further …
A Spectroscopic Survey Of Wise -Selected Obscured Quasars With The Southern African Large Telescope, Kevin N. Hainline, Ryan C. Hickox, Christopher M. Carroll, Adam D. Myers
A Spectroscopic Survey Of Wise -Selected Obscured Quasars With The Southern African Large Telescope, Kevin N. Hainline, Ryan C. Hickox, Christopher M. Carroll, Adam D. Myers
Dartmouth Scholarship
We present the results of an optical spectroscopic survey of a sample of 40 candidate obscured quasars identified on the basis of their mid-infrared emission detected by the Wide-Field Infrared Survey Explorer (WISE). Optical spectra for this survey were obtained using the Robert Stobie Spectrograph on the Southern African Large Telescope. Our sample was selected with WISE colors characteristic of active galactic nuclei (AGNs), as well as red optical to mid-IR colors indicating that the optical/UV AGN continuum is obscured by dust. We obtain secure redshifts for the majority of the objects that comprise our sample (35/40), and …
A Uv To Mid-Ir Study Of Agn Selection, Sun Mi Chung, Christopher S. Kochanek, Roberto Assef, Michael J. I. Brown, Daniel Stern, Buell T. Jannuzi, Anthony H. Gonzalez, Ryan C. Hickox, John Moustakas
A Uv To Mid-Ir Study Of Agn Selection, Sun Mi Chung, Christopher S. Kochanek, Roberto Assef, Michael J. I. Brown, Daniel Stern, Buell T. Jannuzi, Anthony H. Gonzalez, Ryan C. Hickox, John Moustakas
Dartmouth Scholarship
We classify the spectral energy distributions (SEDs) of 431,038 sources in the 9 deg2 Boötes field of the NOAO Deep Wide-Field Survey (NDWFS). There are up to 17 bands of data available per source, including ultraviolet (GALEX), optical (NDWFS), near-IR (NEWFIRM), and mid-infrared (IRAC and MIPS) data, as well as spectroscopic redshifts for ~20,000 objects, primarily from the AGN and Galaxy Evolution Survey. We fit galaxy, active galactic nucleus (AGN), stellar, and brown dwarf templates to the observed SEDs, which yield spectral classes for the Galactic sources and photometric redshifts and galaxy/AGN luminosities for the extragalactic sources. …
The Angular Clustering Of Infrared-Selected Obscured And Unobscured Quasars, M. A. Dipompeo, A. D. Myers, R. C. Hickox, J. E. Geach, K. N. Hainline
The Angular Clustering Of Infrared-Selected Obscured And Unobscured Quasars, M. A. Dipompeo, A. D. Myers, R. C. Hickox, J. E. Geach, K. N. Hainline
Dartmouth Scholarship
Recent studies of luminous infrared-selected active galactic nuclei (AGN) suggest that the reddest, most obscured objects display a higher angular clustering amplitude, and thus reside in higher-mass dark matter halos. This is a direct contradiction to the prediction of the simplest unification-by-orientation models of AGN and quasars. However, clustering measurements depend strongly on the "mask" that removes low-quality data and describes the sky and selection function. We find that applying a robust, conservative mask to WISE-selected quasars yields a weaker but still significant difference in the bias between obscured and unobscured quasars. These findings are consistent with results from previous …
Gemini Long-Slit Observations Of Luminous Obscured Quasars: Further Evidence For An Upper Limit On The Size Of The Narrow-Line Region, Kevin N. Hainline, Ryan C. Hickox, Jenny E. Greene, Adam D. Myers
Gemini Long-Slit Observations Of Luminous Obscured Quasars: Further Evidence For An Upper Limit On The Size Of The Narrow-Line Region, Kevin N. Hainline, Ryan C. Hickox, Jenny E. Greene, Adam D. Myers
Dartmouth Scholarship
We examine the spatial extent of the narrow-line regions (NLRs) of a sample of 30 luminous obscured quasars at 0.4 < z < 0.7 observed with spatially resolved Gemini-N GMOS long-slit spectroscopy. Using the [O III] λ5007 emission feature, we estimate the size of the NLR using a cosmology-independent measurement: the radius where the surface brightness falls to 10–15 erg s–1 cm–2 arcsec–2. We then explore the effects of atmospheric seeing on NLR size measurements and conclude that direct measurements of the NLR size from observed profiles are too large by 0.1-0.2 dex on average, as compared to measurements made to best-fit Sérsic or Voigt profiles convolved with the seeing. These data, which span a full order of magnitude in IR luminosity (log (L 8 μm/erg s–1) = 44.4-45.4), …
Massive Compact Galaxies With High-Velocity Outflows: Morphological Analysis And Constraints On Agn Activity, P. H. Sell, C. A. Tremonti, R. C. Hickox, A. M. Diamond-Stanic
Massive Compact Galaxies With High-Velocity Outflows: Morphological Analysis And Constraints On Agn Activity, P. H. Sell, C. A. Tremonti, R. C. Hickox, A. M. Diamond-Stanic
Dartmouth Scholarship
We investigate the process of rapid star formation quenching in a sample of 12 massive galaxies at intermediate redshift (z~0.6) that host high-velocity ionized gas outflows (v>1000 km/s). We conclude that these fast outflows are most likely driven by feedback from star formation rather than active galactic nuclei (AGN). We use multiwavelength survey and targeted observations of the galaxies to assess their star formation, AGN activity, and morphology. Common attributes include diffuse tidal features indicative of recent mergers accompanied by bright, unresolved cores with effective radii less than a few hundred parsecs. The galaxies are extraordinarily compact for their …
Black Hole Variability And The Star Formation-Active Galactic Nucleus Connection: Do All Star-Forming Galaxies Host An Active Galactic Nucleus?, Ryan C. Hickox, James R. Mullaney, David M. Alexander, Chien-Ting J. Chen, Francesca M. Civano, Andy D. Goulding, Kevin N. Hainline
Black Hole Variability And The Star Formation-Active Galactic Nucleus Connection: Do All Star-Forming Galaxies Host An Active Galactic Nucleus?, Ryan C. Hickox, James R. Mullaney, David M. Alexander, Chien-Ting J. Chen, Francesca M. Civano, Andy D. Goulding, Kevin N. Hainline
Dartmouth Scholarship
We investigate the effect of active galactic nucleus (AGN) variability on the observed connection between star formation and black hole accretion in extragalactic surveys. Recent studies have reported relatively weak correlations between observed AGN luminosities and the properties of AGN hosts, which has been interpreted to imply that there is no direct connection between AGN activity and star formation. However, AGNs may be expected to vary significantly on a wide range of timescales (from hours to Myr) that are far shorter than the typical timescale for star formation (100 Myr). This variability can have important consequences for observed correlations. We …
Salt Long-Slit Spectroscopy Of Luminous Obscured Quasars: An Upper Limit On The Size Of The Narrow-Line Region?, Kevin N. Hainline, Ryan Hickox, Jenny E. Greene, Adam D. Myers, Nadia L. Zakamska
Salt Long-Slit Spectroscopy Of Luminous Obscured Quasars: An Upper Limit On The Size Of The Narrow-Line Region?, Kevin N. Hainline, Ryan Hickox, Jenny E. Greene, Adam D. Myers, Nadia L. Zakamska
Dartmouth Scholarship
We present spatially resolved long-slit spectroscopy from the Southern African Large Telescope (SALT) to examine the spatial extent of the narrow-line regions (NLRs) of a sample of 8 luminous obscured quasars at 0.10 < z < 0.43. Our results are consistent with an observed shallow slope in the relationship between NLR size and L_[OIII], which has been interpreted to indicate that NLR size is limited by the density and ionization state of the NLR gas rather than the availability of ionizing photons. We also explore how the NLR size scales with a more direct measure of instantaneous AGN power using mid-IR photometry from WISE, which probes warm to hot dust near the central black hole and so, unlike [OIII], does not depend on the properties of the NLR. Using our results as well as samples from the literature, we obtain a power-law relationship between NLR size and L_8micron that is significantly steeper than that observed for NLR size and L_[OIII]. We find that the size of the NLR goes approximately as L^(1/2)_8micron, as expected from the simple scenario of constant-density clouds illuminated by a central ionizing source. We further see tentative evidence for a flattening of the relationship between NLR size and L_8micron at the high luminosity end, and propose that we are seeing a limiting NLR size of 10 - 20 kpc, beyond which the availability of gas to ionize becomes too low. We find that L_[OIII] ~ L_8micron^(1.4), consistent with a picture in which the L_[OIII] is dependent on the volume of the NLR. These results indicate that high-luminosity quasars have a strong effect in ionizing the available gas in a galaxy.
A Redline Starburst: Co(2-1) Observations Of An Eddington-Limited Galaxy Reveal Star Formation At Its Most Extreme, J. E. Geach, R. C. Hickox, A. M. Diamond-Stanic, M. Krips
A Redline Starburst: Co(2-1) Observations Of An Eddington-Limited Galaxy Reveal Star Formation At Its Most Extreme, J. E. Geach, R. C. Hickox, A. M. Diamond-Stanic, M. Krips
Dartmouth Scholarship
We report observations of the CO(2-1) emission of SDSSJ1506+54, a compact (r_e~135pc) starburst galaxy at z=0.6. SDSSJ1506+54 appears to be forming stars close to the limit allowed by stellar radiation pressure feedback models: the measured L_IR/L'_CO 1500 is one of the highest measured for any galaxy. With its compact optical morphology but extended low surface brightness envelope, post-starburst spectral features, high infrared luminosity (L_IR>10^12.5 L_Sun), low gas fraction (M_H2/M_stars~15%), and short gas depletion time (tens of Myr), we speculate that this is a feedback- limited central starburst episode at the conclusion of a major merger. Taken as such, SDSSJ1504+54 …
High-Velocity Outflows Without Agn Feedback: Eddington-Limited Star Formation In Compact Massive Galaxies, Aleksandar M. Diamond-Stanic, John Moustakas, Christy A. Tremonti, Alison L. Coil, Ryan C. Hickox
High-Velocity Outflows Without Agn Feedback: Eddington-Limited Star Formation In Compact Massive Galaxies, Aleksandar M. Diamond-Stanic, John Moustakas, Christy A. Tremonti, Alison L. Coil, Ryan C. Hickox
Dartmouth Scholarship
We present the discovery of compact, obscured star formation in galaxies at z ~ 0.6 that exhibit 1000 km s–1 outflows. Using optical morphologies from the Hubble Space Telescope and infrared photometry from the Wide-field Infrared Survey Explorer, we estimate star formation rate (SFR) surface densities that approach ΣSFR ≈ 3000 M ☉ yr–1 kpc–2, comparable to the Eddington limit from radiation pressure on dust grains. We argue that feedback associated with a compact starburst in the form of radiation pressure from massive stars and ram pressure from supernovae and stellar winds is sufficient …
The Clustering Of Ha Emitters At Z=2.23 From Hizels, J. E. Geach, D. Sobral, R. C. Hickox, D. A. Wake
The Clustering Of Ha Emitters At Z=2.23 From Hizels, J. E. Geach, D. Sobral, R. C. Hickox, D. A. Wake
Dartmouth Scholarship
We present a clustering analysis of 370 high-confidence Hα emitters (HAEs) at z = 2.23. The HAEs are detected in the Hi-Z Emission Line Survey (HiZELS), a large-area blank field 2.121 μm narrow-band survey using the United Kingdom Infrared Telescope Wide Field Camera (WFCAM). Averaging the two-point correlation function of HAEs in two ∼1° scale fields [United Kingdom Infrared Deep Sky Survey/Ultra Deep Survey (UDS) and Cosmological Evolution Survey (COSMOS) fields] we find a clustering amplitude equivalent to a correlation length of r0 = 3.7 ± 0.3 h−1 Mpc for galaxies with star formation rates of ≳7 M⊙ yr−1. The …
The Acs Survey Of Galactic Globular Clusters. Xi. The Three-Dimensional Orientation Of The Sagittarius Dwarf Spheroidal Galaxy And Its Globular Clusters, Michael H. H. Siegel, Steven R. Majewski, David R. Law, Ata Sarajedini, Aaron Dotter, A Marín-Franch, Brian Chaboyer
The Acs Survey Of Galactic Globular Clusters. Xi. The Three-Dimensional Orientation Of The Sagittarius Dwarf Spheroidal Galaxy And Its Globular Clusters, Michael H. H. Siegel, Steven R. Majewski, David R. Law, Ata Sarajedini, Aaron Dotter, A Marín-Franch, Brian Chaboyer
Dartmouth Scholarship
We use observations from the Hubble Space Telescope Advanced Camera for Surveys (HST/ACS) study of Galactic globular clusters to investigate the spatial distribution of the inner regions of the disrupting Sagittarius dwarf spheroidal galaxy (Sgr). We combine previously published analyses of four Sgr member clusters located near or in the Sgr core (M54, Arp 2, Terzan 7, and Terzan 8) with a new analysis of diffuse Sgr material identified in the background of five low-latitude Galactic bulge clusters (NGC 6624, 6637, 6652, 6681, and 6809) observed as part of the ACS survey. By comparing the bulge cluster color-magnitude …
Dynamical Masses Of Early-Type Galaxies: A Comparison To Lensing Results And Implications For The Stellar Initial Mass Function And The Distribution Of Dark Matter, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner, S. Seitz
Dynamical Masses Of Early-Type Galaxies: A Comparison To Lensing Results And Implications For The Stellar Initial Mass Function And The Distribution Of Dark Matter, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner, S. Seitz
Dartmouth Scholarship
This work aims to study the distribution of the luminous and dark matter in Coma early-type galaxies. Dynamical masses obtained under the assumption that mass follows light do not match with the masses of strong gravitational lens systems of similar velocity dispersions. Instead, dynamical fits with dark matter haloes are in good agreement with lensing results. We derive mass-to-light ratios of the stellar populations from Lick absorption line indices, reproducing well the observed galaxy colours. Even in dynamical models with dark matter haloes the amount of mass that follows the light increases more rapidly with the galaxy velocity dispersion than …
The Double Galaxy Cluster Abell 2465 - I. Basic Properties: Optical Imaging And Spectroscopy, Gary A. Wegner
The Double Galaxy Cluster Abell 2465 - I. Basic Properties: Optical Imaging And Spectroscopy, Gary A. Wegner
Dartmouth Scholarship
Optical imaging and spectroscopic observations of the z= 0.245 double galaxy cluster Abell 2465 are described. This object appears to be undergoing a major merger. It is a double X-ray source and is detected in the radio at 1.4 GHz. The purpose of this paper is to investigate signatures of the interaction of the two components. Redshifts were measured to determine velocity dispersions and virial radii of each component. The technique of fuzzy clustering was used to assign membership weights to the galaxies in each clump. Using redshifts of 93 cluster members within 1.4 Mpc of the subcluster centres, …
Colours Of Bulges And Discs Within Galaxy Clusters And The Signature Of Disc Fading On Infall, Michael J. Hudson, Jeffrey B. Stevenson, Russell J. Smith, Gary A. Wegner
Colours Of Bulges And Discs Within Galaxy Clusters And The Signature Of Disc Fading On Infall, Michael J. Hudson, Jeffrey B. Stevenson, Russell J. Smith, Gary A. Wegner
Dartmouth Scholarship
The origins of the bulge and disc components of galaxies are of primary importance to understanding galaxy formation. Here bulge–disc decomposition is performed simultaneously in B and R bands for 922 bright galaxies in eight nearby (z < 0.06) clusters with deep redshift coverage using photometry from the National Optical Astronomy Observatory (NOAO) Fundamental Plane Survey. The total galaxy colours follow a universal colour–magnitude relation (CMR). The discs of L* galaxies are 0.24 mag bluer in B−R than bulges. Bulges have a significant CMR slope while the CMR slope of discs is flat. Thus the slope of the CMR of the total light is driven primarily (60 per cent) by the bulge CMR, and to a lesser extent (40 per cent) by the change in the bulge‐to‐total ratio …
Stirring Up The Pot: Can Cooling Flows In Galaxy Clusters Be Quenched By Gas Sloshing?, J. A. A. Zuhone, M. Markevitch, R. E. Johnson
Stirring Up The Pot: Can Cooling Flows In Galaxy Clusters Be Quenched By Gas Sloshing?, J. A. A. Zuhone, M. Markevitch, R. E. Johnson
Dartmouth Scholarship
X-ray observations of clusters of galaxies reveal the presence of edges in surface brightness and temperature, known as "cold fronts." In relaxed clusters with cool cores, these commonly observed edges have been interpreted as evidence for the "sloshing" of the core gas in the cluster's gravitational potential. Such sloshing may provide a source of heat to the cluster core by mixing hot gas from the cluster outskirts with the cool-core gas. Using high-resolution N-body/Eulerian hydrodynamic simulations, we model gas sloshing in galaxy clusters initiated by mergers with subclusters. The simulations include merger scenarios with gas-filled and gasless subclusters. The …
Core Gas Sloshing In Abell 1644, Ryan E. Johnson, Maxim Markevitch, Gary A. Wegner, Christine Jones, William R. Forman
Core Gas Sloshing In Abell 1644, Ryan E. Johnson, Maxim Markevitch, Gary A. Wegner, Christine Jones, William R. Forman
Dartmouth Scholarship
We present an analysis of a 72 ks Chandra observation of the double cluster Abell 1644 (z = 0.047). The X-ray temperatures indicate that the masses are M 500 = (2.6 ± 0.4) × 1014 h –1 M ☉ for the northern sub-cluster and M 500 = (3.1 ± 0.4) × 1014 h –1 M ☉ for the southern, main cluster. We identify a sharp edge in the radial X-ray surface brightness of the main cluster, which we find to be a cold front, with a jump in temperature of a factor of ~3. This edge possesses …
Dark Matter Scaling Relations And The Assembly Epoch Of Coma Early-Type Galaxies, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J Magorrian, E. M. Corsini, G. Wegner
Dark Matter Scaling Relations And The Assembly Epoch Of Coma Early-Type Galaxies, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J Magorrian, E. M. Corsini, G. Wegner
Dartmouth Scholarship
Axisymmetric, orbit-based dynamical models are used to derive dark matter scaling relations for Coma early-type galaxies. From faint to bright galaxies, halo core radii and asymptotic circular velocities increase. Compared to spirals of the same brightness, the majority of Coma early-type galaxies—those with old stellar populations—have similar halo core radii but more than two times larger asymptotic halo velocities. The average dark matter density inside 2 r eff decreases with increasing luminosity and is 6.8 times larger than in disk galaxies of the same B-band luminosity. Compared at the same stellar mass, dark matter densities in ellipticals are 13.5 …
The Acs Survey Of Galactic Globular Clusters. Vi. Ngc 6366: A Heavily Stripped Galactic Globular Cluster, Nathaniel E. Q. Paust, Antonio Aparicio, Giampaolo Piotto, I. Neill Reid, Jay Anderson, Ata Sarajedini, Luigi R. Bedin, Brian Chaboyer
The Acs Survey Of Galactic Globular Clusters. Vi. Ngc 6366: A Heavily Stripped Galactic Globular Cluster, Nathaniel E. Q. Paust, Antonio Aparicio, Giampaolo Piotto, I. Neill Reid, Jay Anderson, Ata Sarajedini, Luigi R. Bedin, Brian Chaboyer
Dartmouth Scholarship
We have used observations obtained as part of the Hubble Space Telescope/ACS Survey of Galactic globular clusters (GCs) to construct a color-magnitude diagram for the bulge cluster, NGC 6366. The luminosity function derived from those data extends to M F606W ~ 9, or masses of ~0.3 M ☉. Unlike most GCs, the mass function peaks near the main-sequence turnoff with significantly fewer low-mass stars even after correction for completeness and mass segregation. Using a multimass King model, we extrapolate the global cluster behavior and find the global mass function to be poorly matched by a power law, with …
Ages And Metallicities Of Early-Type Void Galaxies From Line Strength Measurements, Gary Wegner, Norman A. Grogin
Ages And Metallicities Of Early-Type Void Galaxies From Line Strength Measurements, Gary Wegner, Norman A. Grogin
Dartmouth Scholarship
We present spectroscopic observations of 26 galaxies of type E and S0, based on their blue morphologies, located in voids by the study of Grogin & Geller in 1999. Measurements of redshift, velocity dispersion, and four Lick line indices, Mg b , Fe5270, Fe5335, and Hβ with their errors are given for all of these galaxies, along with Hβ, [O III], Hα, and [N II] emission line strengths for a subset of these objects. These sources are brighter than M* for low-density regions and tend to be bluer than their counterpart early-type objects in high-density regions. Using the models …
The Noao Fundamental Plane Survey - Iii. Variations In The Stellar Populations Of Red-Sequence Galaxies From The Cluster Core To The Virial Radius, Russell J. S. Smith, Michael J. Hudson, John R. Lucey, Jenica E. Nelan, Gary A. Wegner
The Noao Fundamental Plane Survey - Iii. Variations In The Stellar Populations Of Red-Sequence Galaxies From The Cluster Core To The Virial Radius, Russell J. S. Smith, Michael J. Hudson, John R. Lucey, Jenica E. Nelan, Gary A. Wegner
Dartmouth Scholarship
We analyse absorption line-strength indices for ~3000 red-sequence galaxies in 94 nearby clusters, to investigate systematic variations of their stellar content with location in the host cluster. The data are drawn from the NOAO Fundamental Plane Survey. Our adopted method is a generalization of that introduced by Nelan et al. to determine the global age-mass and metallicity-mass relations from the same survey. We find strong evidence for a change in galaxy properties, at fixed mass, over a range from the cluster centre to the virial radius, R_200. For example, red-sequence galaxies further out in the clusters have weaker Mgb5177 (at …
The Oxford-Dartmouth Thirty Degree Survey - Ii. Clustering Of Bright Lyman Break Galaxies: Strong Luminosity-Dependent Bias At Z = 4, Paul D. Allen, Leonidas A. Moustakas, Gavin Dalton, Emily Macdonald, Chris Blake, Lee Clewley, Catherine Heymans, Gary Wegner
The Oxford-Dartmouth Thirty Degree Survey - Ii. Clustering Of Bright Lyman Break Galaxies: Strong Luminosity-Dependent Bias At Z = 4, Paul D. Allen, Leonidas A. Moustakas, Gavin Dalton, Emily Macdonald, Chris Blake, Lee Clewley, Catherine Heymans, Gary Wegner
Dartmouth Scholarship
We present measurements of the clustering properties of bright (L > L*) z~4 Lyman break galaxies (LBGs) selected from the Oxford-Dartmouth Thirty Degree Survey (ODT). We describe techniques used to select and evaluate our candidates and calculate the angular correlation function, which we find best fitted by a power law, ω(θ) =Awθ−β with Aw= 15.4 (with θ in arcsec), using a constrained slope of β= 0.8. Using a redshift distribution consistent with photometric models, we deproject this correlation function and find a comoving Mpc in a Ωm= 0.3 flat λ cosmology for iAB≤ 24.5. This corresponds to a linear bias value …
Structural Properties Of Discs And Bulges Of Early-Type Galaxies, Roelof S. De Jong, Luc Simard, Roger L. Davies, R. P. Saglia, David Burstein, Matthew Colless, Robert Mcmahan, Gary Wegner
Structural Properties Of Discs And Bulges Of Early-Type Galaxies, Roelof S. De Jong, Luc Simard, Roger L. Davies, R. P. Saglia, David Burstein, Matthew Colless, Robert Mcmahan, Gary Wegner
Dartmouth Scholarship
We have used the EFAR sample of galaxies to investigate the light distributions of early-type galaxies. We decompose the two-dimensional light distribution of the galaxies in a flattened spheroidal component with a Sérsic radial light profile and an inclined disc component with an exponential light profile. We show that if we assume that all galaxies can have a spheroidal and a disc component, then the brightest, bulge-dominated elliptical galaxies have a fairly broad distribution in the Sérsic profile shape parameter nB, with a median of approximately 3.7 and with σ∼ 0.9. Other galaxies have smaller nB values. …
The Oxford-Dartmouth Thirty Degree Survey - I. Observations And Calibration Of A Wide-Field Multiband Survey, Emily C. Macdonald, Paul Allen, Gavin Dalton, Leonidas A. Moustakas, Catherine Heymans, Edward Edmondso N, Chris Blake, Lee Clewley, Molly C. Hammell, Ed Olding, Lance Miller, Steve Rawlings, Jasper Wall, Gary Wegner, Christian Wolf
The Oxford-Dartmouth Thirty Degree Survey - I. Observations And Calibration Of A Wide-Field Multiband Survey, Emily C. Macdonald, Paul Allen, Gavin Dalton, Leonidas A. Moustakas, Catherine Heymans, Edward Edmondso N, Chris Blake, Lee Clewley, Molly C. Hammell, Ed Olding, Lance Miller, Steve Rawlings, Jasper Wall, Gary Wegner, Christian Wolf
Dartmouth Scholarship
The Oxford–Dartmouth Thirty Degree Survey (ODTS) is a deep, wide, multiband imaging survey designed to cover a total of 30 deg2 in BV Ri′Z, with a subset of U- and K-band data, in four separate fields of 5–10 deg2 centred at 00:18:24 +34:52, 09:09:45 +40:50, 13:40:00 +02:30 and 16:39:30 +45:24. Observations have been made using the Wide Field Camera on the 2.5-m Isaac Newton Telescope (INT) in La Palma to average limiting depths (5σ Vega, aperture magnitudes) of U= 24.8, B= 25.6, V= 25.0, R= 24.6 and i′= …
Spatially Resolved Spectroscopy Of Coma Cluster Early-Type Galaxies - Ii. The Minor Axis Dataset, G. Wegner, E. M. Corsini, R. P. Saglia, R. Bender
Spatially Resolved Spectroscopy Of Coma Cluster Early-Type Galaxies - Ii. The Minor Axis Dataset, G. Wegner, E. M. Corsini, R. P. Saglia, R. Bender
Dartmouth Scholarship
We present minor axis, offset major axis and one diagonal long slit spectra for 10 E and S0 galaxies of the Coma cluster drawn from a magnitude-limited sample studied before. We derive rotation curves, velocity dispersion profiles and the H3 and H4 coefficients of the Hermite decomposition of the line of sight velocity distribution. Moreover, we derive the line index profiles of Mg, Fe and Hβ line indices and assess their errors. The data will be used to construct dynamical models of the galaxies and study their stellar populations.
Comparing The Sfi Peculiar Velocities With The Pscz Gravity Field: A Velmod Analysis, E. Branchini, W. Freudling, L. N. Da Costa, C. S. Frenk, R. Giovanelli, M. P. Haynes, J. J. Salzer, G. Wegner, I. Zehavi
Comparing The Sfi Peculiar Velocities With The Pscz Gravity Field: A Velmod Analysis, E. Branchini, W. Freudling, L. N. Da Costa, C. S. Frenk, R. Giovanelli, M. P. Haynes, J. J. Salzer, G. Wegner, I. Zehavi
Dartmouth Scholarship
We compare the peculiar velocities derived from the I-band Tully–Fisher (TF) relation for 989 field spiral galaxies in the SFI catalogue with the predicted velocity field derived from the IRAS PSCz galaxy redshift survey. We assume linear gravitational instability theory and apply the maximum likelihood technique, VELMOD to SFI galaxies within a redshift cz LG =6000 km s−1. The resulting calibration of the TF relation is consistent with a previous, independent calibration for a similar sample of spirals residing in clusters. Our analysis provides an accurate estimate of the quantity βI ≡ Ωm0.6 …