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Articles 1 - 30 of 68
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Automated Algorithm For The Identification Of Artifacts In Mottled And Noisy Images, Onome Augustine Ugbeme, Eli S. Saber, Wencheng Wu, Kartheek Chandu
Automated Algorithm For The Identification Of Artifacts In Mottled And Noisy Images, Onome Augustine Ugbeme, Eli S. Saber, Wencheng Wu, Kartheek Chandu
Articles
We describe a method for automatically classifying image-quality defects on printed documents. The proposed approach accepts a scanned image where the defect has been localized a priori and performs several appropriate image processing steps to reveal the region of interest. A mask is then created from the exposed region to identify bright outliers. Morphological reconstruction techniques are then applied to emphasize relevant local attributes. The classification of the defects is accomplished via a customized tree classifier that utilizes size or shape attributes at corresponding nodes to yield appropriate binary decisions. Applications of this process include automated/assisted diagnosis and repair of …
The Complexity Of Computing The Size Of An Interval, Lane A. Hemaspaandra, Christopher M. Homan, Sven Kosub, Klaus W. Wagner
The Complexity Of Computing The Size Of An Interval, Lane A. Hemaspaandra, Christopher M. Homan, Sven Kosub, Klaus W. Wagner
Articles
Given a p-order A over a universe of strings (i.e., a transitive, reflexive, antisymmetric relation such that if (x, y) ∈ A then |x| is polynomially bounded by |y|), an interval size function of A returns, for each string x in the universe, the number of strings in the interval between strings b(x) and t(x) (with respect to A), where b(x) and t(x) are functions that are polynomial-time computable in the length of x. By choosing sets of interval size functions based on feasibility requirements for their underlying p-orders, we obtain new characterizations of complexity classes. We prove that the …
Cosmological Constraints From The Sdss Luminous Red Galaxies, Max Tegmark, Daniel J. Eisenstein, Michael Strauss, David H. Weinberg, Michael R. Blanton, Joshua A. Frieman, Masataka Fukugita, James E. Gunn, Andrew J. S. Hamilton, Gillian R. Knapp, Robert C. Nichol, Jeremiah P. Ostriker, Nikhil Padmanabhan, Will J. Percival, David J. Schlegel, Donald P. Schneider, Roman Scoccimarro, Uroš Seljak, Hee-Jong Seo, Molly Swanson, Alexander S. Szalay, Michael S. Vogeley, Jaiyul Yoo, Idit Zehavi, Kevork Abazajian, Scott F. Anderson, James Annis, Neta A. Bahcall, Bruce Bassett, Andreas Berlind, John Brinkman, Tamás Budavari, Francisco Castander, Andrew Connolly, Istvan Csabai, Mamoru Doi, Douglas P. Finkbeiner, Bruce Gillespie, Karl Glazebrook, Gregory S. Hennessy, David W. Hogg, Željko Ivezić, Bhuvnesh Jain, David Johnston, Stephen Kent, Donald Q. Lamb, Brian C. Lee, Huan Lin, Jon Loveday, Robert H. Lupton, Jeffrey A. Munn, Kaike Pan, Changbom Park, John Peoples, Jeffrey R. Pier, Adrian Pope, Michael Richmond, Constance Rockosi, Ryan Scranton, Ravi K. Sheth, Albert Stebbins, Christopher Stoughton, István Szapudi, Douglas L. Tucker, Daniel E. Vanden Berk, Brian Yanny, Donald G. York
Cosmological Constraints From The Sdss Luminous Red Galaxies, Max Tegmark, Daniel J. Eisenstein, Michael Strauss, David H. Weinberg, Michael R. Blanton, Joshua A. Frieman, Masataka Fukugita, James E. Gunn, Andrew J. S. Hamilton, Gillian R. Knapp, Robert C. Nichol, Jeremiah P. Ostriker, Nikhil Padmanabhan, Will J. Percival, David J. Schlegel, Donald P. Schneider, Roman Scoccimarro, Uroš Seljak, Hee-Jong Seo, Molly Swanson, Alexander S. Szalay, Michael S. Vogeley, Jaiyul Yoo, Idit Zehavi, Kevork Abazajian, Scott F. Anderson, James Annis, Neta A. Bahcall, Bruce Bassett, Andreas Berlind, John Brinkman, Tamás Budavari, Francisco Castander, Andrew Connolly, Istvan Csabai, Mamoru Doi, Douglas P. Finkbeiner, Bruce Gillespie, Karl Glazebrook, Gregory S. Hennessy, David W. Hogg, Željko Ivezić, Bhuvnesh Jain, David Johnston, Stephen Kent, Donald Q. Lamb, Brian C. Lee, Huan Lin, Jon Loveday, Robert H. Lupton, Jeffrey A. Munn, Kaike Pan, Changbom Park, John Peoples, Jeffrey R. Pier, Adrian Pope, Michael Richmond, Constance Rockosi, Ryan Scranton, Ravi K. Sheth, Albert Stebbins, Christopher Stoughton, István Szapudi, Douglas L. Tucker, Daniel E. Vanden Berk, Brian Yanny, Donald G. York
Articles
We measure the large-scale real-space power spectrum P(k) using luminous red galaxies (LRGs) in the Sloan Digital Sky Survey (SDSS) and use this measurement to sharpen constraints on cosmological parameters from the Wilkinson Microwave Anisotropy Probe (WMAP). We employ a matrix-based power spectrum estimation method using Pseudo-Karhunen-Lo`eve eigenmodes, producing uncorrelated minimum-variance measurements in 20 k-bands of both the clustering power and its anisotropy due to redshift-space distortions, with narrow and well-behaved window functions in the range 0.01 h/Mpc < k < 0.2 h/Mpc. Results from the LRG and main galaxy samples are consistent, with the former providing higher signal-to-noise. Our results are robust to omitting angular and radial density fluctuations and are consistent between different parts of the sky. They provide a striking confirmation of the predicted large-scale CDM power spectrum. Combining only SDSS LRG and WMAP data places robust constraints on many cosmological parameters that complement prior analyses of multiple data sets. The LRGs provide independent cross-checks on m and the baryon fraction in good agreement with WMAP. Within the context of flat CDM models, our LRG measurements complementWMAP by sharpening the constraints on the matter density, the neutrino density and the tensor amplitude by about a factor of two, giving m = 0.24±0.02 (1 ), Pmν < 0.9 eV (95%) and r < 0.3 (95%). Baryon oscillations are clearly detected and provide a robust measurement of the comoving distance to the median survey redshift z = 0.35 independent of curvature and dark energy properties. Within the CDM framework, our power spectrum measurement improves the evidence for spatial flatness, sharpening the curvature constraint tot = 1.05±0.05 from WMAP alone to tot = 1.003±0.010. Assuming tot = 1, the equation of state parameter is constrained to w = −0.94±0.09, indicating the potential for more ambitious future LRG measurements to provide precision tests of the nature of dark energy. All these constraints are essentially independent of scales k > 0.1h/Mpc and associated nonlinear complications, yet agree well with more aggressive published analyses where nonlinear modeling is crucial.
The Acs Virgo Cluster Survey. Xiv. Analysis Of Color-Magnitude Relations In Globular Cluster Systems, Steffen Mieske, Andres Jordan, Patrick Cote
The Acs Virgo Cluster Survey. Xiv. Analysis Of Color-Magnitude Relations In Globular Cluster Systems, Steffen Mieske, Andres Jordan, Patrick Cote
Articles
We examine the correlation between globular cluster (GC) color and magnitude using HST/ACS imaging for a sample of 79 early-type galaxies (−21.7 < MB < −15.2 mag) with accurate surfacebrightness fluctuation distances from the ACS Virgo Cluster Survey. Using the KMM mixture modeling algorithm, we find a highly significant correlation, z ≡ d(g−z) dz = −0.037 ± 0.004, between color and magnitude for the subpopulation of blue GCs in the co-added GC color-magnitude diagram of the three brightest Virgo cluster galaxies (M49, M87 and M60). The sense of the correlation is such that brighter GCs are redder than their fainter counterparts. For the single GC systems of M87 and M60, we find similar correlations; M49 does not appear to show a significant trend. There is no correlation between (g − z) and Mz for GCs belonging to the red subpopulation. The correlation g ≡ d(g−z) dg for the blue subpopulation is much weaker than z. Using Monte Carlo simulations, we attribute this finding to the fact that the blue subpopulation in Mg extends to higher luminosities than does the red subpopulation, which biases the KMM fit results. The highly significant correlation between color and Mz, however, is a real effect: this conclusion is supported by biweight fits to the same color distributions. We identify two environmental dependencies which influence the derived color-magnitude relation: (1) the slope of the color-magnitude relation decreases in significance with decreasing galaxy luminosity, although it remains detectable over the full luminosity range of our sample; and (2) the slope is stronger for GC populations located at smaller galactocentric distances. These characteristics suggest that the observed trend is, at least partially, shaped by external agents. We examine several physical mechanisms that might give rise to the observed color-magnitude relation including: (1) presence of contaminants like super-clusters, stripped galactic nuclei, or ultra-compact dwarfs; (2) accretion of GCs from low-mass galaxies; (3) stochastic effects; (4) the capture of field stars by individual GCs; and (5) GC self-enrichment. Although none of these scenarios offers a fully satisfactory explanation of the observations, we conclude that self-enrichment and field-star capture, or a combination of these processes, offer the most promising means of explaining our observations.
Tass Mark Iv Photometric Survey Of The Northern Sky, Thomas Droege, Michael Richmond, Michael Sallman, Robert P. Creager
Tass Mark Iv Photometric Survey Of The Northern Sky, Thomas Droege, Michael Richmond, Michael Sallman, Robert P. Creager
Articles
The Amateur Sky Survey (TASS) is a loose confederation of amateur and professional astronomers. We describe the design and construction of our Mark IV systems, a set of wide-field telescopes with CCD cameras which take simultaneous images in the V and IC passbands. We explain our observational procedures and the pipeline which processes and reduces the images into lists of stellar positions and magnitudes. We have compiled a large database of measurements for stars in the northern celestial hemisphere with V -band magnitudes in the range 7 < V < 13. This paper describes data taken over the four-year period starting November, 2001. One of our results is a catalog of repeated measurements on the Johnson-Cousins system for over 4.3 million stars.
Contribution Of Stellar Tidal Disruptions To The X-Ray Luminosity Function Of Active Galaxies, Miloš Milosavljević, David Merritt, Luis C. Ho
Contribution Of Stellar Tidal Disruptions To The X-Ray Luminosity Function Of Active Galaxies, Miloš Milosavljević, David Merritt, Luis C. Ho
Articles
The luminosity function of active galactic nuclei has been measured down to luminosities ∼ 1042 ergs s-1 in the soft and hard X-rays. Some fraction of this activity is associated with the accretion of the material liberated by the tidal disruption of stars by massive black holes. We estimate the contribution to the X-ray luminosity function from the tidal disruption process. While the contribution depends on a number poorly known parameters, it appears that it can account for the majority of X-ray selected AGN with soft or hard Xray luminosities . 1043 - 1044 ergs s-1. If this is correct, …
There Is No 2-(22,8,4) Block Design, Richard Bilous, Clement W.H. Lam, Larry H. Thiel, Ben P.C. Li, G.H. John Van Rees, Stanislaw P. Radziszowski, Wolfgang H. Holzmann, Hadi Kharaghani
There Is No 2-(22,8,4) Block Design, Richard Bilous, Clement W.H. Lam, Larry H. Thiel, Ben P.C. Li, G.H. John Van Rees, Stanislaw P. Radziszowski, Wolfgang H. Holzmann, Hadi Kharaghani
Articles
In this paper we show that a 2-(22, 8, 4) design does not exist. This result was obtained by a computer search.
Trends In The Globular Cluster Luminosity Function Of Early-Type Galaxies, Andrés Jordán, Dean E. Mclaughlin, Patrick Côté, David Merritt, Et Al.
Trends In The Globular Cluster Luminosity Function Of Early-Type Galaxies, Andrés Jordán, Dean E. Mclaughlin, Patrick Côté, David Merritt, Et Al.
Articles
We present results from a study of the globular cluster luminosity function (GCLF) in a sample of 89 earlytype galaxies observed as part of the ACS Virgo Cluster Survey. Using a Gaussian parametrization of the GCLF, we find a highly significant correlation between the GCLF dispersion, , and the galaxy luminosity, MB,gal, in the sense that the GC systems in fainter galaxies have narrower luminosity functions. The GCLF dispersions in the Milky Way and M31 are fully consistent with this trend, implying that the correlation between sigma and galaxy luminosity is more fundamental than older suggestions that GCLF shape is …
A Hybrid Thermal Video And Ftir Spectrometer System For Rapidly Locating And Characterizing Gas Leaks, David J. Williams, Winthrop Wadsworth, Carl Salvaggio, David W. Messinger
A Hybrid Thermal Video And Ftir Spectrometer System For Rapidly Locating And Characterizing Gas Leaks, David J. Williams, Winthrop Wadsworth, Carl Salvaggio, David W. Messinger
Articles
Undiscovered gas leaks, known as fugitive emissions, in chemical plants and refinery operations can impact regional air quality and present a loss of product for industry. Surveying a facility for potential gas leaks can be a daunting task. Industrial leak detection and repair programs can be expensive to administer. An efficient, accurate and cost effective method for detecting and quantifying gas leaks would both save industries money by identifying production losses and improve regional air quality. Specialized thermal video systems have proven effective in rapidly locating gas leaks. These systems, however, do not have the spectral resolution for compound identification. …
Small Ramsey Numbers, Stanislaw Radziszowski
Small Ramsey Numbers, Stanislaw Radziszowski
Articles
We present data which, to the best of our knowledge, includes all known nontrivial values and bounds for specific graph, hypergraph and multicolor Ramsey numbers, where the avoided graphs are complete or complete without one edge. Many results pertaining to other more studied cases are also presented. We give references to all cited bounds and values, as well as to previous similar compilations. We do not attempt complete coverage of asymptotic behavior of Ramsey numbers, but concentrate on their specific values.
Minimal Rankings And The A-Rank Number Of A Path, Victor Kostyuk, Darren Narayan, Victoria Shults
Minimal Rankings And The A-Rank Number Of A Path, Victor Kostyuk, Darren Narayan, Victoria Shults
Articles
Given a graph G, a function f:V(G)→ {1,2,…,k} is a k-ranking of G if f(u)=f(v) implies every u-v path contains a vertex w such that f(w)>f(u). A k-ranking is minimal if the reduction of any label greater than 1 violates the described ranking property. The arank number of a graph, denoted ψr(G), is the largest k such that G has a minimal k-ranking. We present new results involving minimal k-rankings of paths. In particular, we determine ψr(Pn), a problem posed by Laskar and Pillone in 2000 (Refer to PDF file for exact formulas).
Modeling The Spectral Effects Of Water And Soil As Surface Contaminants In A High Resolution Optical Image Simulation, Kristin Strackerjan, Lon Smith, John Kerekes
Modeling The Spectral Effects Of Water And Soil As Surface Contaminants In A High Resolution Optical Image Simulation, Kristin Strackerjan, Lon Smith, John Kerekes
Articles
The primary interest of this research is to introduce selected environmental effects into RIT’s Digital Imaging and Remote Sensing Image Generation (DIRSIG) Model. DIRSIG is capable of producing high resolution images (meter scale) using Computer Aided Design models (CAD) of buildings, vehicles, trees, etc. across the full optical spectrum (0.35-25μm). Currently, these objects are modeled in a pristine manner and there is no option to simulate them after exposure to environmental effects. Ideally, we would like to subject a given material to these environmental effects and then accurately model the modified reflected or emitted spectrum. As a first step, we …
A Survey Of Kiloparsec-Scale Radio Outflows In Radio-Quiet Active Galactic Nuclei, Jack F. Gallimore, David Axon, Christopher P. O'Dea, Stefi A. Baum, Alan Pedlar
A Survey Of Kiloparsec-Scale Radio Outflows In Radio-Quiet Active Galactic Nuclei, Jack F. Gallimore, David Axon, Christopher P. O'Dea, Stefi A. Baum, Alan Pedlar
Articles
Seyfert galaxies commonly host compact jets spanning 10—100 pc scales, but larger structures are resolved out in long baseline, aperture synthesis surveys. Previous, targeted studies showed that kiloparsec-scale radio structures (KSRs) may be a common feature of Seyfert and LINER galaxies, and the origin of KSRs may be starburst or AGN. We report a new Very Large Array (VLA) survey of a complete sample of Seyfert and LINER galaxies. Out of all of the surveyed radio-quiet sources, we find that 44% (19 / 43) show extended radio structures at least 1 kpc in total extent that do not match the …
Optical Polarimetry Of The Jets Of Nearby Radio Galaxies. I. The Data, Eric Perlman, Alex Padgett, Markos Georganopoulos, Christopher P. O'Dea, Stefi A. Baum, Et Al.
Optical Polarimetry Of The Jets Of Nearby Radio Galaxies. I. The Data, Eric Perlman, Alex Padgett, Markos Georganopoulos, Christopher P. O'Dea, Stefi A. Baum, Et Al.
Articles
In this paper, the first in a series, we present an overview of new Hubble Space Telescope (HST) imaging polarimetry of six nearby radio galaxies (3C 15, 3C 66B, 3C 78, 3C 264, 3C 346, and 3C 371) with optical jets. These observations triple the number of extragalactic jets with subarcsecond-resolution optical polarimetry. We discuss the polarization characteristics of each jet and, as our Stokes I images also represent by far the deepest optical images yet obtained of each of these jets, we also discuss the morphology in total flux of each jet in detail. We find evidence of high …
Automatic Tie Point Selection Using Laplacian Of Gaussian (Log) Spatial Filtering, Seth Weith-Glushko, Karl Walli, Carl Salvaggio
Automatic Tie Point Selection Using Laplacian Of Gaussian (Log) Spatial Filtering, Seth Weith-Glushko, Karl Walli, Carl Salvaggio
Articles
This research examines the utility of an automated image registration technique that utilizes the Laplacian of Gaussian filter to extract semi-invariant ground control points, the use of matrix transformations for efficient management of affine image relationships, and wavelet theory for multi-resolution analysis. Additionally, advances in both composite and predictive transformations will be covered. Results will be presented that demonstrate the utility of these techniques for processing large data sets such as HyVista Corporation’s HyMap sensor. Automation techniques will be highlighted, demonstrating the strengths and weaknesses when applied to images with high degrees of parallax, cloud-cover, and other types of temporal …
A Fundamental Relation Between Compact Stellar Nuclei, Supermassive Black Holes, And Their Host Galaxies, Laura Ferrarese, Patrick Côté, Elena Dalla Bontà, David Merritt, Et Al.
A Fundamental Relation Between Compact Stellar Nuclei, Supermassive Black Holes, And Their Host Galaxies, Laura Ferrarese, Patrick Côté, Elena Dalla Bontà, David Merritt, Et Al.
Articles
Imaging surveys with the Hubble Space Telescope (HST) have shown that 50–80% of low- and intermediate-luminosity galaxies contain a compact stellar nucleus at their center, regardless of host galaxy morphological type. We combine HST imaging for early-type galaxies from the ACS Virgo Cluster Survey with ground-based long-slit spectra from KPNO to show that the masses of compact stellar nuclei in Virgo Cluster galaxies obey a tight correlation with the masses of the host galaxies. The same correlation is obeyed by the supermassive black holes (SBHs) found in predominantly massive galaxies. The compact stellar nuclei in the Local Group galaxies M33 …
Note: Computation Of The Ramsey Number R(W5,K5), Stanislaw Radziszowski, Josh Stinehour, Kung-Kuen Tse
Note: Computation Of The Ramsey Number R(W5,K5), Stanislaw Radziszowski, Josh Stinehour, Kung-Kuen Tse
Articles
We determine the value of the Ramsey number R(W5;K5) to be 27, where W5 = K1 + C4 is the 4-spoked wheel of order 5. This solves one of the four remaining open cases in the tables given in 1989 by George R. T. Hendry, which included the Ramsey numbers R(G;H) for all pairs of graphs G and H having ve vertices, except seven entries. In addition, we show that there exists a unique up to isomorphism critical Ramsey graph for W5 versus K5. Our results are based on computer algorithms.
Photographic Scanning, Or "Strip" Photography, With A Polaroid Camera, Andrew Davidhazy
Photographic Scanning, Or "Strip" Photography, With A Polaroid Camera, Andrew Davidhazy
Articles
Preprint: https://ritdml.rit.edu/dspace/handle/1850/1663 A shorter and more up to date version of another article (instant strip) describing how to modify a Polaroid camera for strip photography. This article was intended for a high school audience.
Instant Strip Photography, Andrew Davidhazy
Instant Strip Photography, Andrew Davidhazy
Articles
||Postprint: https://ritdml.rit.edu/dspace/handle/1850/1690 Making strip cameras out of Polaroid pack-film type cameras.
Efficient Merger Of Binary Supermassive Black Holes In Non-Axisymmetric Galaxies, Peter Berczik, David Merritt, Rainer Spurzem, Hans-Peter Bischof
Efficient Merger Of Binary Supermassive Black Holes In Non-Axisymmetric Galaxies, Peter Berczik, David Merritt, Rainer Spurzem, Hans-Peter Bischof
Articles
Binary supermassive black holes form naturally in galaxy mergers, but their long-termevolution is uncertain. In spherical galaxies, N-body simulations show that binary evolution stalls at separations much too large for significant emission of gravitational waves (the “final parsec problem”). Here, we follow the long-term evolution of a massive binary in more realistic, triaxial and rotating galaxy models. We find that the binary does not stall. The binary hardening rates that we observe are sufficient to allow complete coalescence of binary SBHs in 10 Gyr or less, even in the absence of collisional loss-cone refilling or gas-dynamical torques, thus providing a …
Demonstration Quality Scanning Digital Camera, Andrew Davidhazy
Demonstration Quality Scanning Digital Camera, Andrew Davidhazy
Articles
Another offshoot of the article below [article is located at: https://ritdml.rit.edu/dspace/handle/1850/1557 ].Work is based on the use of a linear CCD array removed from a cheap hand scanner and installed in a 35mm camera body for doing peripheral, panoramic and image plane scanning.
Lossless Compression Of Color Palette Images With One-Dimensional Techniques, Ziya Arnavut, Ferat Sahin
Lossless Compression Of Color Palette Images With One-Dimensional Techniques, Ziya Arnavut, Ferat Sahin
Articles
Palette images are widely used on the World Wide Web (WWW) and in game-cartridge applications. Many images used on the WWW are stored and transmitted after they are compressed losslessly with the standard graphics interchange format (GIF), or portable network graphics (PNG). Well-known 2-D compression schemes, such as JPEG-LS and JPEG-2000, fail to yield better compression than GIF or PNG due to the fact that the pixel values represent indices that point to color values in a look-up table. To improve the compression performance of JPEG-LS and JPEG-2000 techniques, several researchers have proposed various reindexing algorithms. We investigate various compression …
Streaming Motions Toward The Supermassive Black Hole In Ngc 1097, Kambiz Fathi, Thaisa Storchi-Bergmann, Rogemar A. Riffel, Claudia Winge, David J. Axon, Andew Robinson, Alessandro Marconi
Streaming Motions Toward The Supermassive Black Hole In Ngc 1097, Kambiz Fathi, Thaisa Storchi-Bergmann, Rogemar A. Riffel, Claudia Winge, David J. Axon, Andew Robinson, Alessandro Marconi
Articles
We have used GMOS-IFU and high resolution HST-ACS observations to map, in unprecedented detail, the gas velocity field and structure within the 0.7 kpc circumnuclear ring of the SBb LINER/Seyfert 1 galaxy NGC 1097. We find clear evidence of radial streaming motions associated with spiral structures leading to the unresolved (< 3.5 parsecs) nucleus, which we interpret as part of the fueling chain by which gas is transported to the nuclear starburst and supermassive black hole.
The Supermassive Black Hole In Centaurus A: A Benchmark For Gas Kinematical Measurements, Alessandro Marconi, Guia Pastorini, Franco Pacini, David J. Axon, A. Capetti, D. Macchetto, A. M. Koekemoer, E. J. Shreier
The Supermassive Black Hole In Centaurus A: A Benchmark For Gas Kinematical Measurements, Alessandro Marconi, Guia Pastorini, Franco Pacini, David J. Axon, A. Capetti, D. Macchetto, A. M. Koekemoer, E. J. Shreier
Articles
We present new HST/STIS observations of Centaurus A. [SIII] 9533A was used to study the kinematics in the nuclear region with a 0.1" spatial resolution. The STIS data and the VLT/ISAAC spectra by Marconi et al. (2001) provide independent and consistent measures of the BH mass, which are in agreement with our previous estimate based on the ISAAC data alone: MBH=(1.1+/-0.1) 10^8 Msun for a disk inclination of i=25deg or or MBH=(6.5+/-0.7) 10^7 Msun for i=35deg, the largest i value allowed by the data. We find that the choice of the intrinsic surface brightness distribution, a crucial element in the …
The Acs Virgo Cluster Survey Ix: The Color Distributions Of Globular Cluster Systems In Early-Type Galaxies, Eric Peng, Andres Jordan, Patrick Cote
The Acs Virgo Cluster Survey Ix: The Color Distributions Of Globular Cluster Systems In Early-Type Galaxies, Eric Peng, Andres Jordan, Patrick Cote
Articles
We present the color distributions of globular cluster (GC) systems for 100 Virgo cluster earlytype galaxies observed in the ACS Virgo Cluster Survey, the deepest and most homogeneous survey of this kind to date. While the color distributions of individual GC systems can show significant variations from one another, their general properties are consistent with continuous trends across galaxy luminosity, color, and stellar mass. On average, galaxies at all luminosities in our study (−22 < MB < −15) appear to have bimodal or asymmetric GC color distributions. Almost all galaxies possess a component of metal-poor GCs, with the average fraction of metal-rich GCs ranging from 15 to 60%. The colors of both subpopulations correlate with host galaxy luminosity and color, with the red GCs having a steeper slope. The steeper correlation seen in the mean color of the entire GC system is driven by the increasing fraction of metal-rich GCs for more luminous galaxies. To convert color to metallicity, we also introduce a preliminary (g–z)-[Fe/H] relation calibrated to Galactic, M49 and M87 GCs. This relation is nonlinear with a steeper slope for [Fe/H] . −0.8. As a result, the metallicities of the metal-poor and metal-rich GCs vary similarly with respect to galaxy luminosity and stellar mass, with relations of [Fe/H]MP ∝ L0.16±0.04 ∝ M0.17±0.04 ⋆ and [Fe/H]MR ∝ L0.26±0.03 ∝ M0.22±0.03 ⋆ , respectively. Although these relations are shallower than the mass-metallicity relation predicted by wind models and observed for dwarf galaxies, they are very similar to the mass-metallicity relation for star forming galaxies in the same mass range. The offset between the two GC populations varies slowly (∝ M0.05 ⋆ ) and is approximately 1 dex across three orders of magnitude in mass, suggesting a nearly universal amount of enrichment between the formation of the two populations of GCs. We also find that although the metal-rich GCs show a larger dispersion in color, it is the metal-poor GCs that have an equal or larger dispersion in metallicity. The similarity in the M⋆–[Fe/H] relations for the two populations, implies that the conditions of GC formation for metal-poor and metal-rich GCs could not have been too different. Like the color-magnitude relation, these relations derived from globular clusters present stringent constraints on the formation and evolution of early-type galaxies.
The Acs Virgo Cluster Survey. Ix. The Color Distributions Of Globular Cluster Systems In Early-Type Galaxies, Eric W. Peng, Andrés Jordán, Patrick Côté, John P. Blakeslee, Laura Ferrarese, Simona Mei, Michael J. West, David Merritt, Milos Milosavljević, John L. Tonry
The Acs Virgo Cluster Survey. Ix. The Color Distributions Of Globular Cluster Systems In Early-Type Galaxies, Eric W. Peng, Andrés Jordán, Patrick Côté, John P. Blakeslee, Laura Ferrarese, Simona Mei, Michael J. West, David Merritt, Milos Milosavljević, John L. Tonry
Articles
We present the color distributions of globular cluster (GC) systems for 100 Virgo cluster early-type galaxies observed in the ACS Virgo Cluster Survey, the deepest and most homogeneous survey of this kind to date. While the color distributions of individual GC systems can show significant variations from one another, their general properties are consistent with continuous trends across galaxy luminosity, color, and stellar mass. On average, galaxies at all luminosities in our study (−22 < MB < −15) appear to have bimodal or asymmetric GC color distributions. Almost all galaxies possess a component of metal-poor GCs, with the average fraction of metal-rich GCs ranging from 15 to 60%. The colors of both subpopulations correlate with host galaxy luminosity and color, with the red GCs having a steeper slope. The steeper correlation seen in the mean color of the entire GC system is driven by the increasing fraction of metal-rich GCs for more luminous galaxies. To convert color to metallicity, we also introduce a preliminary (g–z)-[Fe/H] relation calibrated to Galactic, M49 and M87 GCs. This relation is nonlinear with a steeper slope for [Fe/H] . −0.8. As a result, the metallicities of the metal-poor and metal-rich GCs vary similarly with respect to galaxy luminosity and stellar mass, with relations of [Fe/H]MP ∝ L0.16±0.04 ∝ M0.17±0.04 and [Fe/H]MR ∝ L0.26±0.03 ∝ M0.22±0.03, respectively. Although these relations are shallower than the mass-metallicity relation predicted by wind models and observed for dwarf galaxies, they are very similar to the mass-metallicity relation for star forming galaxies in the same mass range. The offset between the two GC populations varies slowly (∝ M0.05) and is approximately 1 dex across three orders of magnitude in mass, suggesting a nearly universal amount of enrichment between the formation of the two populations of GCs. We also find that although the metal-rich GCs show a larger dispersion in color, it is the metal-poor GCs that have an equal or larger dispersion in metallicity. The similarity in the M–[Fe/H] relations for the two populations, implies that the conditions of GC formation for metal-poor and metal-rich GCs could not have been too different. Like the color-magnitude relation, these relations derived from globular clusters present stringent constraints on the formation and evolution of early-type galaxies.
Massive Star Formation In The Central Regions Of Spiral Galaxies, Johan H. Knapen, Lisa M. Mazzuca, Torsten Böker, I. Shlosman, L. Colina, F. Combes, David J. Axon
Massive Star Formation In The Central Regions Of Spiral Galaxies, Johan H. Knapen, Lisa M. Mazzuca, Torsten Böker, I. Shlosman, L. Colina, F. Combes, David J. Axon
Articles
The morphology of massive star formation in the central regions of galaxies is an important tracer of the dynamical processes that govern the evolution of disk, bulge, and nuclear activity. Aims: We present optical imaging of the central regions of a sample of 73 spiral galaxies in the H alpha line and in optical broad bands, and derive information on the morphology of massive star formation. Methods: We obtained images with the William Herschel Telescope, mostly at a spatial resolution of below one second of arc. For most galaxies, no H alpha imaging is available in the literature. We outline …
Atomic Hydrogen In The One-Sided "Compact Double" Radio Galaxy 2050+364, Rene C. Vermeulen, Alvaro Labiano, Peter D. Barthel, Stefi A. Baum, W. H. De Vries, Christopher P. O'Dea
Atomic Hydrogen In The One-Sided "Compact Double" Radio Galaxy 2050+364, Rene C. Vermeulen, Alvaro Labiano, Peter D. Barthel, Stefi A. Baum, W. H. De Vries, Christopher P. O'Dea
Articles
European VLBI Network spectral imaging of the “compact double” radio source 2050+364 in the UHF band at 1049 MHz has resolved the HI absorbing region, and has shown a faint continuum component to the North (N), in addition to the well-known East-West double (E, W). Re-examination of VLBI continuum images at multiple frequencies suggests that 2050+364 may well be a one-sided core-jet source, which appears as a double over a limited frequency range. One of the dominant features,W, would then be the innermost visible portion of the jet, and could be at or adjacent to the canonical radio core. The …
Hi Absorption In 3c 49 And 3c 268.3. Probing The Environment Of Compact Steep Spectrum And Ghz Peaked Spectrum Sources, Alvaro Labiano, Rene C. Vermeulen, Peter D. Barthel, Christopher P. O'Dea, J. F. Gallimore, Stefi A. Baum, W. De Vries
Hi Absorption In 3c 49 And 3c 268.3. Probing The Environment Of Compact Steep Spectrum And Ghz Peaked Spectrum Sources, Alvaro Labiano, Rene C. Vermeulen, Peter D. Barthel, Christopher P. O'Dea, J. F. Gallimore, Stefi A. Baum, W. De Vries
Articles
We present and discuss European VLBI Network UHF band spectral line observations, made to localise the redshifted 21cm HI absorption known to occur in the subgalactic sized compact steep spectrum galaxies 3C 49 and 3C 268.3. We have detected HI absorption towards the western radio lobe of 3C 49 and the northern lobe of 3C 268.3. However, we cannot rule out the presence of similar amounts of HI towards the opposite and much fainter lobes. The radio lobes with detected HI absorption (1) are brighter and closer to the core than the opposite lobes; (2) are depolarized; and (3) are …
Brownian Motion Of Black Holes In Dense Nuclei, David Merritt, Frederik Laun
Brownian Motion Of Black Holes In Dense Nuclei, David Merritt, Frederik Laun
Articles
We evaluate the Brownian motion of a massive particle ("black hole") at the center of a galaxy using N-body simulations. Our galaxy models have power-law central density cusps like those observed at the centers of elliptical galaxies. The simulations show that the black hole achieves a steady-state kinetic energy that is substantially different than would be predicted based on the properties of the galaxy model in the absence of the black hole. The reason appears to be that the black hole responds to stars whose velocities have themselves been raised by the presence of the black hole. Over a wide …