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Articles 1 - 24 of 24
Full-Text Articles in Physical Sciences and Mathematics
Extreme Ultraviolet Quasar Colours From Galex Observations Of The Sdss Dr14q Catalogue, Daniel E. Vanden Berk, Sarah C. Wesolowski, Mary J. Yeckley, Joseph M. Marcinik, Jean M. Quashnock, Lawrence M. Machia, Jian Wu
Extreme Ultraviolet Quasar Colours From Galex Observations Of The Sdss Dr14q Catalogue, Daniel E. Vanden Berk, Sarah C. Wesolowski, Mary J. Yeckley, Joseph M. Marcinik, Jean M. Quashnock, Lawrence M. Machia, Jian Wu
Computer Science Faculty Publications
The rest-frame far to extreme ultraviolet (UV) colour–redshift relationship has been constructed from data on over 480,000 quasars carefully cross-matched between SDSS Data Release 14 and the final GALEX photometric catalogue. UV matching and detection probabilities are given for all the quasars, including dependencies on separation, optical brightness, and redshift. Detection limits are also provided for all objects. The UV colour distributions are skewed redward at virtually all redshifts, especially when detection limits are accounted for. The median GALEX far-UV minus near-UV (FUV − NUV) colour–redshift relation is reliably determined up to z ≈ 2.8, corresponding to rest-frame wavelengths as …
A Hierarchical Model For The Ages Of Galactic Halo White Dwarfs, Shijing Si, Ted Von Hippel, David A. Van Dyk, Elliot Robinson, Aaron Webster, Et Al.
A Hierarchical Model For The Ages Of Galactic Halo White Dwarfs, Shijing Si, Ted Von Hippel, David A. Van Dyk, Elliot Robinson, Aaron Webster, Et Al.
Ted von Hippel
In astrophysics, we often aim to estimate one or more parameters for each member object in a population and study the distribution of the fitted parameters across the population. In this paper, we develop novel methods that allow us to take advantage of existing software designed for such case-by-case analyses to simultaneously fit parameters of both the individual objects and the parameters that quantify their distribution across the population. Our methods are based on Bayesian hierarchical modelling which is known to produce parameter estimators for the individual objects that are on average closer to their true values than estimators based …
Fourier Transform Spectroscopy Of The C³Δ-X³Δ Transition Of Tio In Support Of Exoplanet Spectroscopy, James N. Hodges, Peter Bernath
Fourier Transform Spectroscopy Of The C³Δ-X³Δ Transition Of Tio In Support Of Exoplanet Spectroscopy, James N. Hodges, Peter Bernath
Chemistry & Biochemistry Faculty Publications
Recent limitations in the TiO line list used in cross-correlation detection schemes have made the detection and quantification of TiO in exoplanetary atmospheres challenging. The quality of the line list appears to degrade at wavelengths shorter than 630 nm. The C3Δ-X3Δ electronic transition has strong rovibronic bands near 500 nm. In an effort to improve the line list, a spectrum of TiO in a furnace at 1950 K is analyzed, and the assigned lines of the C3Δ-X3Δ transition are fit with the N2 Hamiltonian in the molecular spectrum fitting software, PGOPHER …
A Hierarchical Model For The Ages Of Galactic Halo White Dwarfs, Shijing Si, Ted Von Hippel, David A. Van Dyk, Elliot Robinson, Aaron Webster, Et Al.
A Hierarchical Model For The Ages Of Galactic Halo White Dwarfs, Shijing Si, Ted Von Hippel, David A. Van Dyk, Elliot Robinson, Aaron Webster, Et Al.
Publications
In astrophysics, we often aim to estimate one or more parameters for each member object in a population and study the distribution of the fitted parameters across the population. In this paper, we develop novel methods that allow us to take advantage of existing software designed for such case-by-case analyses to simultaneously fit parameters of both the individual objects and the parameters that quantify their distribution across the population. Our methods are based on Bayesian hierarchical modelling which is known to produce parameter estimators for the individual objects that are on average closer to their true values than estimators based …
A Multiwavelength Continuum Characterization Of High-Redshift Broad Absorption Line Quasars, D. Tuccillo, G. Bruni, M. A. Dipompeo, M. S. Brotherton
A Multiwavelength Continuum Characterization Of High-Redshift Broad Absorption Line Quasars, D. Tuccillo, G. Bruni, M. A. Dipompeo, M. S. Brotherton
Dartmouth Scholarship
We present the results of a multiwavelength study of a sample of high-redshift radio-loud (RL) broad absorption line (BAL) quasars. This way, we extend to higher redshift previous studies on the radio properties and broad-band optical colours of these objects. We have selected a sample of 22 RL BAL quasars with 3.6 ≤ z ≤ 4.8 cross-correlating the FIRST radio survey with the Sloan Digital Sky Survey (SDSS). Flux densities between 1.25 and 9.5 GHz have been collected with the Jansky Very Large Array and Effelsberg-100 m telescopes for 15 BAL and 14 non-BAL quasars used as a comparison sample. …
Gama/H-Atlas : Common Star Formation Rate Indicators And Their Dependence On Galaxy Physical Parameters., L. Wang, P. Norberg, M. L. P. Gunawardhana, S. Heinis, I. K. Baldry, J. Bland-Hawthorn, N. Bourne, S. Brough, M. J. I. Brown, M. E. Cluver, A. Cooray, E. Da Cunha, S. P. Driver, L. Dunne, S. Dye, S. Eales, M. W. Grootes, Benne W. Holwerda, A. M. Hopkins, E. Ibar, R. Ivison, C. Lacey, M. A. Lara-Lopez, J. Loveday, S. J. Maddox, M. J. Michalowski, I. Oteo, M. S. Owers, C. C. Popescu, D. J. B. Smith, E. N. Taylor, R. J. Tuffs, P. Van Der Werf
Gama/H-Atlas : Common Star Formation Rate Indicators And Their Dependence On Galaxy Physical Parameters., L. Wang, P. Norberg, M. L. P. Gunawardhana, S. Heinis, I. K. Baldry, J. Bland-Hawthorn, N. Bourne, S. Brough, M. J. I. Brown, M. E. Cluver, A. Cooray, E. Da Cunha, S. P. Driver, L. Dunne, S. Dye, S. Eales, M. W. Grootes, Benne W. Holwerda, A. M. Hopkins, E. Ibar, R. Ivison, C. Lacey, M. A. Lara-Lopez, J. Loveday, S. J. Maddox, M. J. Michalowski, I. Oteo, M. S. Owers, C. C. Popescu, D. J. B. Smith, E. N. Taylor, R. J. Tuffs, P. Van Der Werf
Benne Holwerda
We compare common star formation rate (SFR) indicators in the local Universe in the Galaxy and Mass Assembly (GAMA) equatorial fields (∼160 deg2), using ultraviolet (UV) photometry from GALEX, far-infrared and sub-millimetre (sub-mm) photometry from Herschel Astrophysical Terahertz Large Area Survey, and Hα spectroscopy from the GAMA survey. With a high-quality sample of 745 galaxies (median redshift z = 0.08), we consider three SFR tracers: UV luminosity corrected for dust attenuation using the UV spectral slope β (SFRUV, corr), Hα line luminosity corrected for dust using the Balmer decrement (BD) (SFRH α, corr), and the combination of UV and infrared …
Gama/H-Atlas : Common Star Formation Rate Indicators And Their Dependence On Galaxy Physical Parameters., L. Wang, P. Norberg, M. L. P. Gunawardhana, S. Heinis, I. K. Baldry, J. Bland-Hawthorn, N. Bourne, S. Brough, M. J. I. Brown, M. E. Cluver, A. Cooray, E. Da Cunha, S. P. Driver, L. Dunne, S. Dye, S. Eales, M. W. Grootes, Benne W. Holwerda, A. M. Hopkins, E. Ibar, R. Ivison, C. Lacey, M. A. Lara-Lopez, J. Loveday, S. J. Maddox, M. J. Michalowski, I. Oteo, M. S. Owers, C. C. Popescu, D. J. B. Smith, E. N. Taylor, R. J. Tuffs, P. Van Der Werf
Gama/H-Atlas : Common Star Formation Rate Indicators And Their Dependence On Galaxy Physical Parameters., L. Wang, P. Norberg, M. L. P. Gunawardhana, S. Heinis, I. K. Baldry, J. Bland-Hawthorn, N. Bourne, S. Brough, M. J. I. Brown, M. E. Cluver, A. Cooray, E. Da Cunha, S. P. Driver, L. Dunne, S. Dye, S. Eales, M. W. Grootes, Benne W. Holwerda, A. M. Hopkins, E. Ibar, R. Ivison, C. Lacey, M. A. Lara-Lopez, J. Loveday, S. J. Maddox, M. J. Michalowski, I. Oteo, M. S. Owers, C. C. Popescu, D. J. B. Smith, E. N. Taylor, R. J. Tuffs, P. Van Der Werf
Faculty Scholarship
We compare common star formation rate (SFR) indicators in the local Universe in the Galaxy and Mass Assembly (GAMA) equatorial fields (∼160 deg2), using ultraviolet (UV) photometry from GALEX, far-infrared and sub-millimetre (sub-mm) photometry from Herschel Astrophysical Terahertz Large Area Survey, and Hα spectroscopy from the GAMA survey. With a high-quality sample of 745 galaxies (median redshift z = 0.08), we consider three SFR tracers: UV luminosity corrected for dust attenuation using the UV spectral slope β (SFRUV, corr), Hα line luminosity corrected for dust using the Balmer decrement (BD) (SFRH α, corr), and the combination of UV and infrared …
Direct Collapse To Supermassive Black Hole Seeds: Comparing The Amr And Sph Approaches, Yang Luo, Kentaro Nagamine, Isaac Shlosman
Direct Collapse To Supermassive Black Hole Seeds: Comparing The Amr And Sph Approaches, Yang Luo, Kentaro Nagamine, Isaac Shlosman
Physics and Astronomy Faculty Publications
We provide detailed comparison between the adaptive mesh refinement (AMR) code ENZO-2.4 and the smoothed particle hydrodynamics (SPH)/N-body code GADGET-3 in the context of isolated or cosmological direct baryonic collapse within dark matter (DM) haloes to form supermassive black holes. Gas flow is examined by following evolution of basic parameters of accretion flows. Both codes show an overall agreement in the general features of the collapse; however, many subtle differences exist. For isolated models, the codes increase their spatial and mass resolutions at different pace, which leads to substantially earlier collapse in SPH than in AMR cases due …
Supermassive Black Hole Seed Formation At High Redshifts: Long-Term Evolution Of The Direct Collapse, Isaac Shlosman, Jun-Hwan Choi, Mitchell C. Begelman, Kentaro Nagamine
Supermassive Black Hole Seed Formation At High Redshifts: Long-Term Evolution Of The Direct Collapse, Isaac Shlosman, Jun-Hwan Choi, Mitchell C. Begelman, Kentaro Nagamine
Physics and Astronomy Faculty Publications
We use cosmological adaptive mesh refinement code enzo zoom-in simulations to study the long-term evolution of the collapsing gas within dark matter haloes at z. This direct collapse process is a leading candidate for rapid formation of supermassive black hole (SMBH) seeds. To circumvent the Courant condition at small radii, we apply the sink particle method, focusing on evolution on scales ∼0.01–10 pc. The collapse proceeds in two stages, with the secondary runaway happening within the central 10 pc. The sink particles form when the collapsing gas requires additional refinement of the grid size at the highest refinement level. …
Observational Properties Of Simulated Galaxies In Overdense And Average Regions At Redshifts Z ≃ 6–12, Hidenobu Yajima, Isaac Shlosman, Emilio Romano-Díaz, Kentaro Nagamine
Observational Properties Of Simulated Galaxies In Overdense And Average Regions At Redshifts Z ≃ 6–12, Hidenobu Yajima, Isaac Shlosman, Emilio Romano-Díaz, Kentaro Nagamine
Physics and Astronomy Faculty Publications
We use high-resolution zoom-in cosmological simulations of galaxies of Romano-Díaz et al., post-processing them with a panchromatic three-dimensional radiation transfer code to obtain the galaxy UV luminosity function (LF) at z ≃ 6–12. The galaxies are followed in a rare, heavily overdense region within a ∼5σ density peak, which can host high-z quasars, and in an average density region, down to the stellar mass of Mstar ∼ 4 × 107 M⊙. We find that the overdense regions evolve at a substantially accelerated pace – the most massive galaxy has grown to Mstar ∼ 8.4 …
Supermassive Black Hole Formation At High Redshifts Via Direct Collapse In A Cosmological Context, Jun-Hwan Choi, Isaac Shlosman, Mitchell C. Begelman
Supermassive Black Hole Formation At High Redshifts Via Direct Collapse In A Cosmological Context, Jun-Hwan Choi, Isaac Shlosman, Mitchell C. Begelman
Physics and Astronomy Faculty Publications
We study the early stage of the formation of seed supermassive black holes via direct collapse in dark matter (DM) haloes, in the cosmological context. We perform high-resolution zoom-in simulations of such collapse at high z. Using the adaptive mesh refinement code enzo, we resolve the formation and growth of a DM halo, until its virial temperature reaches ∼104 K, atomic cooling turns on, and collapse ensues. We demonstrate that direct collapse proceeds in two stages, although they are not well separated. The first stage is triggered by the onset of atomic cooling, and leads to rapidly increasing …
Optical-Faint, Far-Infrared-Bright Herschel Sources In The Candels Fields: Ultra-Luminous Infrared Galaxies At Z > 1 And The Effect Of Source Blending, Haojing Yan, Mauro Stefanon, Zhiyuan Ma, S. P. Willner, Rachel Somerville, Matthew L.N. Ashby, Romeel Davé, Pablo G. Pérez-González, Antonio Cava, Tommy Wiklind, Dale D. Kocevski, Marc Rafelski, Jeyhan Kartaltepe, Asantha Cooray, Anton M. Koekemoer, Norman A. Grogin
Optical-Faint, Far-Infrared-Bright Herschel Sources In The Candels Fields: Ultra-Luminous Infrared Galaxies At Z > 1 And The Effect Of Source Blending, Haojing Yan, Mauro Stefanon, Zhiyuan Ma, S. P. Willner, Rachel Somerville, Matthew L.N. Ashby, Romeel Davé, Pablo G. Pérez-González, Antonio Cava, Tommy Wiklind, Dale D. Kocevski, Marc Rafelski, Jeyhan Kartaltepe, Asantha Cooray, Anton M. Koekemoer, Norman A. Grogin
Physics and Astronomy Faculty Publications
The Herschel very wide field surveys have charted hundreds of square degrees in multiple far-IR (FIR) bands. While the Sloan Digital Sky Survey (SDSS) is currently the best resource for optical counterpart identifications over such wide areas, it does not detect a large number of Herschel FIR sources and leaves their nature undetermined. As a test case, we studied seven "SDSS-invisible," very bright 250 μm sources (S 250 > 55 mJy) in the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey fields where we have a rich multi-wavelength data set. We took a new approach to decompose the FIR sources, using …
The Allen Telescope Array Search For Electrostatic Discharges On Mars, Marin M. Anderson, Andrew P.V. Siemion, William C. Barott, Geoffery C. Bower, Gregory T. Delory, Imke De Pater, Dan Werthimer
The Allen Telescope Array Search For Electrostatic Discharges On Mars, Marin M. Anderson, Andrew P.V. Siemion, William C. Barott, Geoffery C. Bower, Gregory T. Delory, Imke De Pater, Dan Werthimer
William Barott
The Allen Telescope Array was used to monitor Mars between 2010 March 9 and June 2, over a total of approximately 30 hr, for radio emission indicative of electrostatic discharge. The search was motivated by the report from Ruf et al. of the detection of non-thermal microwave radiation from Mars characterized by peaks in the power spectrum of the kurtosis, or kurtstrum, at 10 Hz, coinciding with a large dust storm event on 2006 June 8. For these observations, we developed a wideband signal processor at the Center for Astronomy Signal Processing and Electronics Research. This 1024 channel spectrometer calculates …
Calculating Time Lags From Unevenly Sampled Light Curves, A. Zoghbi, C. Reynolds, E. M. Cackett
Calculating Time Lags From Unevenly Sampled Light Curves, A. Zoghbi, C. Reynolds, E. M. Cackett
Physics and Astronomy Faculty Research Publications
Timing techniques are powerful tools to study dynamical astrophysical phenomena. In the X-ray band, they offer the potential of probing accretion physics down to the event horizon. Recent work has used frequency- and energy-dependent time lags as tools for studying relativistic reverberation around the black holes in several Seyfert galaxies. This was achieved due to the evenly sampled light curves obtained using XMM-Newton. Continuously sampled data are, however, not always available and standard Fourier techniques are not applicable. Here, building on the work of Miller et al., we discuss and use a maximum likelihood method to obtain frequency-dependent lags that …
The Allen Telescope Array Search For Electrostatic Discharges On Mars, Marin M. Anderson, Andrew P.V. Siemion, William C. Barott, Geoffery C. Bower, Gregory T. Delory, Imke De Pater, Dan Werthimer
The Allen Telescope Array Search For Electrostatic Discharges On Mars, Marin M. Anderson, Andrew P.V. Siemion, William C. Barott, Geoffery C. Bower, Gregory T. Delory, Imke De Pater, Dan Werthimer
Department of Electrical Engineering and Computer Science - Daytona Beach
The Allen Telescope Array was used to monitor Mars between 2010 March 9 and June 2, over a total of approximately 30 hr, for radio emission indicative of electrostatic discharge. The search was motivated by the report from Ruf et al. of the detection of non-thermal microwave radiation from Mars characterized by peaks in the power spectrum of the kurtosis, or kurtstrum, at 10 Hz, coinciding with a large dust storm event on 2006 June 8. For these observations, we developed a wideband signal processor at the Center for Astronomy Signal Processing and Electronics Research. This 1024 channel spectrometer calculates …
High-Quality Broadband Bvri Photometry Of Benchmark Open Clusters, Michael Deloss Joner
High-Quality Broadband Bvri Photometry Of Benchmark Open Clusters, Michael Deloss Joner
Theses and Dissertations
Photometric techniques are often used to observe stars and it can be demonstrated that fundamental stellar properties can be observationally determined using calibrated sets of photometric data. Many of the most powerful techniques utilized to calibrate stellar photometry employ the use of stars in clusters since the individual stars are believed to have many common properties such as age, composition, and approximate distance. Broadband photometric Johnson/Cousins BVRI observations are presented for several nearby open clusters. The new photometry has been tested for consistency relative to archival work and shown to be both accurate and precise. The careful use of a …
On Relativistic Disk Spectroscopy In Compact Objects With X-Ray Ccd Cameras, J. M. Miller, A. D'Aì, M. W. Bautz, S. Bhattacharyya, D. N. Burrows, E. M. Cackett, A. C. Fabian, M. J. Freyberg, F. Haberl, J. Kennea, M. A. Nowak, R. C. Reis, T. E. Strohmayer, M. Tsujimoto
On Relativistic Disk Spectroscopy In Compact Objects With X-Ray Ccd Cameras, J. M. Miller, A. D'Aì, M. W. Bautz, S. Bhattacharyya, D. N. Burrows, E. M. Cackett, A. C. Fabian, M. J. Freyberg, F. Haberl, J. Kennea, M. A. Nowak, R. C. Reis, T. E. Strohmayer, M. Tsujimoto
Physics and Astronomy Faculty Research Publications
X-ray charge-coupled devices (CCDs) are the workhorse detectors of modern X-ray astronomy. Typically covering the 0.3-10.0 keV energy range, CCDs are able to detect photoelectric absorption edges and K shell lines from most abundant metals. New CCDs also offer resolutions of 30-50 (E/ΔE), which is sufficient to detect lines in hot plasmas and to resolve many lines shaped by dynamical processes in accretion flows. The spectral capabilities of X-ray CCDs have been particularly important in detecting relativistic emission lines from the inner disks around accreting neutron stars and black holes. One drawback of X-ray CCDs is that spectra can be …
Comparing Various Multi-Component Global Heliosphere Models, H.-R. Müller, V. Florinski, J. Heerikhuisen, V. V. Izmodenov
Comparing Various Multi-Component Global Heliosphere Models, H.-R. Müller, V. Florinski, J. Heerikhuisen, V. V. Izmodenov
Dartmouth Scholarship
Modeling of the global heliosphere seeks to investigate the interaction of the solar wind with the partially ionized local interstellar medium. Models that treat neutr al hydrogen self-consistently and in great detail, together with the plasma, but that neglect magnetic fields, constitute a sub-category within global heliospheric models. There are several different modeling strategies used for this sub-category in the literature. Differences and commonalities in the modeling results from different strategies are pointed out.
An Efficient Targeting Strategy For Multiobject Spectrograph Surveys: The Sloan Digital Sky Survey “Tiling” Algorithm, Michael R. Blanton, Huan Lin, Robert H. Lupton, F. Miller Maley, Neal Young
An Efficient Targeting Strategy For Multiobject Spectrograph Surveys: The Sloan Digital Sky Survey “Tiling” Algorithm, Michael R. Blanton, Huan Lin, Robert H. Lupton, F. Miller Maley, Neal Young
Dartmouth Scholarship
Large surveys using multiobject spectrographs require automated methods for deciding how to efficiently point observations and how to assign targets to each pointing. The Sloan Digital Sky Survey (SDSS) will observe around 106 spectra from targets distributed over an area of about 10,000 deg2 , using a multiobject fiber spectrograph that can simultaneously observe 640 objects in a circular field of view (referred to as a ‘‘ tile ’’) 1= 49 in radius. No two fibers can be placed closer than 5500 during the same observation; multiple targets closer than this distance are said to ‘‘ collide.’’ We present here …
The Warps Survey - Iv. The X-Ray Luminosity-Temperature Relation Of High-Redshift Galaxy Clusters, B. W. Fairley, L. R. Jones, C. Scharf, H. Ebeling, E. Perlman, D. Horner, G. Wegner, M. Malkan
The Warps Survey - Iv. The X-Ray Luminosity-Temperature Relation Of High-Redshift Galaxy Clusters, B. W. Fairley, L. R. Jones, C. Scharf, H. Ebeling, E. Perlman, D. Horner, G. Wegner, M. Malkan
Dartmouth Scholarship
We present a measurement of the cluster X-ray luminosity-temperature (L-T) relation out to high redshift (z∼0.8). Combined ROSAT PSPC spectra of 91 galaxy clusters detected in the Wide Angle ROSAT Pointed Survey (WARPS) are simultaneously fitted in redshift and luminosity bins. The resulting temperature and luminosity measurements of these bins, which occupy a region of the high-redshift L-T relation not previously sampled, are compared with existing measurements at low redshift in order to constrain the evolution of the L-T relation. We find the best fit to low-redshift (z<0.2) cluster data, at T …
Measured Stark Widths And Shifts Of Several Niii Sectral Lines: Temperature Dependence, Stevan Djenize, Vladimir Milosavljevic
Measured Stark Widths And Shifts Of Several Niii Sectral Lines: Temperature Dependence, Stevan Djenize, Vladimir Milosavljevic
Articles
Stark parameters (width and shift) of four doubly ionized nitrogen spectral lines, that belong to 3s-3p and 3p-3d transitions (lower multiplets), have been measured in a linear pulsed, low pressure, arc discharge in the nitrogen-oxygen and helium-nitrogen-oxygen plasmas in a (30 000 - 54 000) K electron temperature and a (0.75 1023 - 2.8 1023) electron density ranges. The measured values have been compared to the existing experimental and calculated data.
Morphological Transformation From Galaxy Harassment, B Moore, G Lake, N Katz
Morphological Transformation From Galaxy Harassment, B Moore, G Lake, N Katz
Astronomy Department Faculty Publication Series
Galaxy morphologies in clusters have undergone a remarkable transition over the past several billion yr. Distant clusters at z ~ 0.4 are filled with small spiral galaxies, many of which are disturbed and show evidence of multiple bursts of star formation. This population is absent from nearby clusters, where spheroidals comprise the faint end of the luminosity function. Our numerical simulations follow the evolution of disk galaxies in a rich cluster resulting from encounters with brighter galaxies and the cluster's tidal field, or "galaxy harassment." After a bursting transient phase, they undergo a complete morphological transformation from "disks" to "spheroidals." …
Recovery Of The Power Spectrum Of Mass Fluctuations From Observations Of The Ly Alpha Forest, Rac Croft, Dh Weinberg, N Katz, L Hernquist
Recovery Of The Power Spectrum Of Mass Fluctuations From Observations Of The Ly Alpha Forest, Rac Croft, Dh Weinberg, N Katz, L Hernquist
Astronomy Department Faculty Publication Series
We present a method to recover the shape and amplitude of the power spectrum of mass fluctuations, P(k), from observations of the high-redshift Lyα forest. The method is motivated by the physical picture that has emerged from hydrodynamic cosmological simulations and related semianalytic models, in which typical Lyα forest lines arise in a diffuse, continuous, fluctuating intergalactic medium. The thermal state of this low-density gas (δρ/ρ 10) is governed by simple physical processes, which lead to a tight correlation between the Lyα optical depth and the underlying matter density. To recover the mass power spectrum, we (1) …
A Rigorous Reanalysis Of The Iras Variable Population: Scale Lengths, Asymmetries, And Microlensing, S Nikolaev, Md Weinberg
A Rigorous Reanalysis Of The Iras Variable Population: Scale Lengths, Asymmetries, And Microlensing, S Nikolaev, Md Weinberg
Astronomy Department Faculty Publication Series
Previous work reported a bar signature in color-selected IRAS variable stars. Here, we estimate the source density of these variables while consistently accounting for spatial incompleteness in the data using a likelihood approach. The existence of the bar is confirmed with a shoulder at a approx 3 kpc, an axis ratio of a:b = 2.2-2.7, and a position angle of 19° ± 1°. The ratio of nonaxisymmetric to axisymmetric components gives a similar estimate for the bar size of a = 3.3 ± 0.1 kpc and a position angle of phi0 = 24° ± 2°. We estimate a scale length …