Astrophysics and Astronomy Commons^™

The Star Formation Rate-Density Relationship At Redshift 3, Nicolas Bouché, James D. Lowenthal

Astronomy: Faculty Publications

We study the star formation rate (SFR) as a function of environment for UV-selected Lyman break galaxies (LBGs) at redshift 3. From deep [μ (sky) ≃ 27.6] UBVI MOSAIC images, covering a total of 0.90 deg , we select 334 LBGs in slices 100 h Mpc (comoving) deep spanning the redshift range 2.9 < z < 3.4 based on Bayesian photometric redshifts that include the I magnitude as a prior. The slice width (100 h Mpc) corresponds to the photometric redshift accuracy (Δ ∼ 0.15). We used mock catalogs from the GIF2 cosmological simulations to show that this redshift resolution is sufficient to statistically differentiate the high-density regions from the low-density regions using ∑ , the projected density to the fifth nearest neighbor. These mock catalogs have a redshift depth of 110 h Mpc, similar to our slice width. The large area of the MOSAIC images, ∼40 × 40 Mpc (comoving) per field, allows us to measure the SFR from the dust-corrected UV continuum as a function of ∑ . In contrast to low-redshift galaxies, we find that the SFR (or UV luminosity) of LBGs at z = 3 shows no detectable dependence on environment over 2 orders of magnitude in densities. To test the significance of our result, we use Monte Carlo simulations (from the mock catalogs) and the same projected density estimators that we applied to our data. We find that we can reject the steep z = 0 SFR-density relation at the 5 σ level. We conclude that the SFR-density relation at z = 3 must be at least 3.6 times flatter than it is locally; i.e., the SFR of LBGs is significantly less dependent on environment than the SFR of local star-forming galaxies. We find that the rest-frame UV colors are also independent of environment.

The Clustering Of Galaxies Around Three Z ∼ 3 Damped Lyα Absorbers, Nicolas Bouché, James D. Lowenthal

Astronomy: Faculty Publications

We present our results on the cross-correlation of Lyman break galaxies (LBGs) around three damped Lyα absorbers (DLAs) at z ≃ 3 from deep [μ (sky) ≃ 27.6 mag arcsec ] UBVI KPNO 4 m/MOSAIC images. The large area of the MOSAIC images, 0.31 deg or ∼65 × 65 h Mpc comoving at redshift z = 3, allows us to probe the clustering of LBGs on scales up to 20 Mpc comoving. Our survey covers a total of 1 deg and contains ∼3000 LBGs with photometric redshifts between 2.8 and 3.5. Using the redshift likelihood distributions with m as a …

Going Slitless: Images Of Forbidden Line Emission Regions Of Classical T Tauri Stars Observed With The Hubble Space Telescope, Patrick Hartigan, Suzan Edwards, Rachel Pierson

Astronomy: Faculty Publications

We have observed five classical T Tauri stars known to have strong forbidden-line emission with STIS in slitless mode on the Hubble Space Telescope. This technique makes it possible to image jets within a few tens of AU of their exciting sources, a region of great interest for models of accretion disks and jets. Slitless images generate emission-line images at all wavelengths, including those where no narrowband filters exist. Images of the forbidden-line regions around each object, constructed by subtracting the stellar continuum and combining observations taken at different orientations, show [O I] jets from CW Tau, HN Tau, …

He I Λ10830 As A Probe Of Winds In Accreting Young Stars, Suzan Edwards, William Fischer, John Kwan, L. Hillenbrand, Andrea K. Dupree

Astronomy: Faculty Publications

He I 10830 profiles acquired with Keck's NIRSPEC for six young low-mass stars with high disk accretion rates (AS 353A, DG Tau, DL Tau, DR Tau, HL Tau, and SVS 13) provide new insight into accretion-driven winds. In four of the stars, the profiles have the signature of resonance scattering, and they possess a deep and broad blueshifted absorption that penetrates more than 50% into the 1 m continuum over a continuous range of velocities from near the stellar rest velocity to the terminal velocity of the wind, unlike inner wind signatures seen in other spectral features. This deep and …

Galaxies At Z = 3 Around Damped Ly-Α Clouds, N. Bouché, James D. Lowenthal

Astronomy: Faculty Publications

We are exploring the connection between Damped Ly-α Absorption systems and Lyman Break Galaxies using deep m (5σ)=26 m - broad band imaging (UBVI) of four wide fields (0.25deg each) obtained at the Kitt Peak 4-m telescope with MOSAIC. Each field contains a DLA at z ∼ 3. We want to address the nature of DLA at high-redshifts: (1) Are the DLAs embedded in much larger systems of galaxies? (2) How does the spatial distribution of emitters in 3D (space and redshift) correlate with the absorber? Contrary to most previous DLA studies, we are not looking for the absorber, and …

Clustering Of Galaxies At Z ∼ 3 Around The Probable Damped Lyα Absorber Toward Qso Apm 08279+5255, Nicolas Bouché, James D. Lowenthal

Astronomy: Faculty Publications

We present results on the clustering of Lyman break galaxies (LBGs) around a probable damped Lyα absorption line cloud (DLA) at z = 2.974 from deep UBVI images of the field containing the quasar APM 08279+5255 (z = 3.91). The large area covered by our images, 0.31 deg or ∼40 × 40 Mpc comoving at redshift z = 3, and their depth, μ (sky) ≃ 27.6 mag arcsec , allow us to identify ∼450 LBG candidates brighter than I = 24.80 at 2. 75 < z < 3.25 both close (50 kpc) to the DLA line of sight and up to 20 Mpc (comoving) from the DLA, i.e., physically unrelated. LBG candidates were identified using photometric redshift techniques that include the I magnitude as a prior estimate in addition to the colors. The two are combined using Bayes's theorem. This helps to break the degeneracies that occur in a pure spectral template fitting scheme. The overall rms is σ ≃ 0.15 at z ∼ 3 based on our analysis of photometric redshifts in the HDF-N. From the redshift likelihood distributions, we selected LBG galaxies within a redshift slice of width W = 0.15(≃ σ ) centered on the redshift of the DLA z . Within that redshift slice, we find an enhancement of galaxies near the DLA using both the surface density (Σ/Σ ≃ 3) and an estimator of the three-dimensional spatial overdensity (n/n̄ ∼ 5 ± 3). The surface overdensity Σ/Σ is significant at the more than 95% significance level on scales 2.5 < r < 5 Mpc comoving. The overdensity cannot be related to the QSO environment since the QSO is at z = 3.91. These results imply that some DLA could reside in high-density regions. We search within 45″ from the line of sight for galaxies responsible for the DLA and find one candidate with Z = 3.03 that is 26″ (145 kpc physical) away. From its magnitude I = 24.65 ± 0.2, its luminosity is M = -21.35. Due to its large impact parameter, however, this galaxy is not a likely candidate for the absorber. abs em I,AB AB z z z abs g g g θ em phot I,AB 2 -2

The Morphology Of Nine Radio-Selected Faint Galaxies From Deep Hubble Space Telescope Imaging, Nathan D. Roche, James D. Lowenthal, David C. Koo

Astronomy: Faculty Publications

Using the Hubble Space Telescope (HST) WFPC2 we perform deep I-band imaging of nine radio-selected [F(8.5 GHz) ≥ 14 μJy] faint galaxies from the Roche, Lowenthal & Koo (2002) sample. Two are also observed in V using HST STIS. Six of the galaxies have known redshifts, in the range 0.4 < z < 1.0. Radial intensity profiles indicate that seven are disc galaxies and two are bulge-dominated. Four of the six with redshifts have a high optical surface brightness in comparison with previous studies of disc galaxies at similar redshifts (e.g. Lilly et al. 1998). The HST imaging reveals that two of the nine galaxies are in close interacting pairs and another five show morphological evidence of recent interactions - two are very asymmetric (A ∼ 0.4) and three have large, luminous rings resembling the collisional starburst rings in the Cartwheel galaxy. For the two ring galaxies with redshifts, we measure ring radii of 7.05 and 10.0 h kpc, which suggest post-collision ages 0.1-0.2 Gyr. One has a fainter inner ring, like the original Cartwheel. The remaining two appear to be late-type barred galaxies and relatively undisturbed. Our HST imaging confirms the high incidence of interactions and dynamical disturbance in faint radio-selected galaxies, as reported by Windhorst et al. and Serjeant et al., for example. In the great majority of these galaxies the high radio luminosities are probably the result of interaction-triggered starbursts. However, one interacting galaxy is a very radio-luminous giant elliptical, with red V - I colours, a normal surface brightness and no evidence of star-forming regions, so its radio source is probably an obscured active galactic nucleus (AGN). The mixture of observed morphologies suggests that enhanced radio luminosities often persist to a late stage of interaction, i.e. at least ∼0.2 Gyr after the perigalactic encounter. asym 50 -1

Keck Spectroscopy And Imaging Of Faint Galaxies Identified As Microjansky Radio Sources, Nathan D. Roche, James D. Lowenthal, David C. Koo

Astronomy: Faculty Publications

We investigate the nature of the faintest radio sources detected in three Very Large Array surveys, to F(8.5 GHz) ∼ 8 μJy. Using the Keck low-resolution imaging spectrograph in BRI and the near-infrared camera in K′ (2.1 μm), we image 51 radio sources, and identify probable optical counterparts for 50. With low-resolution imaging spectroscopy, we successfully acquire new redshifts for 17 sources. Combining these with nine prior redshifts, we can then analyse a sample of 26 sources with spectroscopic redshifts. Based on this sample of 26, we find the largest contribution, about 60 per cent (15), to be from disc …

Helium Emission From Classical T Tauri Stars: Dual Origin In Magnetospheric Infall And Hot Wind, Georgina Beristain, Suzan Edwards, John Kwan

Astronomy: Faculty Publications

High-resolution emission-line profiles of He I and He II in 31 classical T Tauri stars are analyzed with the aim of probing the environs of the star-disk interface in accreting low-mass young stars. The diagnostic power of the helium lines lies in their high-excitation potentials, which restrict their formation to a region either of high temperature or close proximity to a source of ionizing radiation. The He I profiles are decomposed into kinematic components that support the paradigm of magnetically controlled accretion from the disk onto the stellar surface but also require a significant contribution from a hot wind. A …

Hα Imaging With Hubble Space Telescope-Nicmos Of An Elusive Damped Lyα Cloud At Z = 0.61, Nicolas Bouché, James D. Lowenthal, Jane C. Charlton, Matthew A. Bershady, Christopher W. Churchill, Charles C. Steidel

Astronomy: Faculty Publications

Despite previous intensive ground-based imaging and spectroscopic campaigns and wideband Hubble Space Telescope (HST) imaging of the z = 0.927 QSO 3C 336 field, the galaxy that hosts the damped Lyα system along this line of sight has eluded detection. We present a deep narrowband Hα image of the field of this zabs = 0.656 damped Lyα absorber, obtained through the F108N filter of NICMOSI on board the HST. The goal of this project was to detect any Hα emission 10 times closer than previous studies to unveil the damped absorber. We do not detect Hα emission between 0".05 and …

Lyman-Α Imaging Of A Very Luminous Z = 2.3 Starburst Galaxy With Wfpc2, Nathan Roche, James D. Lowenthal, Bruce Woodgate

Astronomy: Faculty Publications

We investigate the Lyα and UV continuum morphology of one of the most luminous known Lymana emitting galaxies (the 'Coup Fourré Galaxy'), associated with a z = 2.3 damped Lyα absorption system in the spectrum of the QSO PHL 957. The galaxy is observed with the Hubble Space Telescope Wide-Field Planetary Camera 2 (HST WFPC2), through a narrow filter (F410M) corresponding to rest-frame Lyα for a total exposure time of 41.2 ks, plus shorter exposures in F555W and F814W. In all three passbands, the galaxy is resolved into a close (∼0.35 arcsec) pair of two components, CFgA and CFgB, both …

Near–Infrared Classification Spectroscopy: H–Band Spectra Of Fundamental Mk Standards, Michael R. Meyer, Suzan Edwards, Kenneth H. Hinkle, Stephen E. Strom

Astronomy: Faculty Publications

We present a catalog of H-band spectra for 85 stars of approximately solar abundance observed at a resolving power of 3000 with the KPNO Mayall 4 m Fourier Transform Spectrometer. The atlas covers spectral types O7M5 and luminosity classes IV as defined in the MK system. We identify both atomic and molecular indices and line ratios that are temperature and luminosity sensitive, allowing spectral classification to be carried out in the H-band. The line ratios permit spectral classification in the presence of continuum excess emission, which is commonly found in premain-sequence or evolved stars. We demonstrate that with …

Near-Infrared Galaxy Counts To J And K ∼ 24 As A Function Of Image Size, Matthew A. Bershady, James D. Lowenthal, David C. Koo

Astronomy: Faculty Publications

We have used the Keck 10 m telescope to count objects as a function of image size in two high Galactic latitude Ðelds covering 1.5 arcmin2 and reaching 50% completeness depths of K \ 24 and J \ 24.5 for stellar sources. Our counts extend D1 mag deeper in K than those of surveys with other telescopes; complement other Keck surveys in the K-band that provide counts at comparable or shallower depths but that have not utilized image structure; and extend by several magnitudes the J-band counts from brighter surveys using smaller telescopes that cover larger areas. We Ðnd the …

Permitted Iron Emission Lines In The Classical T Tauri Star Dr Tauri, Georgina Beristain, Suzan Edwards, John Kwan

Astronomy: Faculty Publications

We present a study of permitted emission lines of Fe I and Fe II in the spectrum of the high-accretion rate classical T Tauri star DR Tau. Echelle spectra collected at the 4 m Mayall telescope at Kitt Peak National Observatory between 1988 and 1992 include four epochs with red spectral coverage (~5000-6800 Å) and three with blue spectral coverage (~4000-4950 Å). A total of 62 unblended Fe I and Fe II lines are identified, their profiles are examined, and ratios of line pairs that are sensitive to column density or temperature are analyzed.

The unblended Fe profiles exhibit a …

Far-Ultraviolet Spectra Of Starburst Galaxies: Stellar Population And The Kinematics Of The Interstellar Medium, Rosa M. Gonzalez Delgado, Claus Leitherer, Timothy Heckman, James D. Lowenthal, Henry C. Ferguson, Carmelle Robert

Astronomy: Faculty Publications

The far-ultraviolet spectra of the four starburst galaxies NGC 6090, Mrk 66, Mrk 1267, and IRAS 0833 + 6517 were observed with the Hopkins Ultraviolet Telescope during the Astro-2 mission. Additional data were obtained for IRAS 0833 + 6517 with the Goddard High-Resolution Spectrograph (GHRS) on the Hubble Space Telescope. We analyze the observations in terms of the stellar content and the kinematics of the interstellar medium, and we discuss the implications of these results for the interpretation of the ultraviolet spectra of high-redshift galaxies. Evolutionary synthesis models are used to constrain the star formation history from the absolute ultraviolet …

Optical Rotation Curves Of Distant Field Galaxies: Sub-L, Systems, Nicole P. Vogt, Andrew C. Phillips, S. M. Faber, Jesús Gallego, Caryl Gronwall, R. Guzmán, Garth D. Illingworth, David C. Koo, James D. Lowenthal

Astronomy: Faculty Publications

Moderate-resolution spectroscopic observations from the Keck 10 m telescope are used to derive internal kinematics for eight faint disk galaxies in the fields flanking the Hubble Deep Field. The spectroscopic data are combined with high-resolution F814W Wide Field Planetary Camera 2 images from the Hubble Space Telescope that provide morphologies, scale lengths, inclinations, and orientations. The eight galaxies have redshifts 0.15 ≲ z ≲ 0.75, magnitudes 18.6 ≤ I ≤ 22.1, and luminosities -21.8 ≤ M ≤ -19.0 (H = 75 km s Mpc and q = 0.05). Terminal disk velocities are derived from the spatially resolved velocity profiles by …

The Panchromatic Starburst Intensity Limit At Low And High Redshift, Gerhardt R. Meurer, Timothy M. Heckman, Matthew D. Lehnert, Claus Leitherer, James D. Lowenthal

Astronomy: Faculty Publications

The integrated bolometric effective surface brightness S distributions of starbursts are investigated for samples observed in (1) the rest frame ultraviolet (UV), (2) the far-infrared and Hα, and (3) 21 cm radio continuum emission. For the UV sample we exploit a tight empirical relationship between UV reddening and extinction to recover the bolometric flux. Parameterizing the S upper limit by the 90th percentile of the distribution, we find a mean S = 2.0×10 L⊙kpc for the three samples, with a factor of 3 difference between the samples. This is consistent with what is expected from the calibration uncertainties alone. We …

The Nature Of Compact Galaxies In The Hubble Deep Field. Ii. Spectroscopic Properties And Implications For The Evolution Of The Star Formation Rate Density Of The Universe, Rafael Guzmán, Jesús Gallego, David C. Koo, Andrew C. Phillips, James D. Lowenthal, S. M. Faber, Garth D. Illingworth, Nicole P. Vogt

Astronomy: Faculty Publications

We present a spectroscopic study of 51 compact field galaxies with redshifts z < 1.4 and apparent magnitudes I < 23.74 in the flanking fields of the Hubble Deep Field. These galaxies are compact in the sense that they have small apparent half-light radii (r ≤ 0″.5) and high surface brightnesses (μ ≤ 22.2 mag arcsec ). The spectra, taken at the Keck telescope, show emission lines in 88% of our sample, and only absorption lines in the remaining 12%. Emission-line profiles are roughly Gaussian with velocity widths that range from the measurement limit of σ ∼ 35 km s to 150 km s . Rest frame [O II] λ3727 equivalent widths range from 5 to 94 Å, yielding star formation rates (SFRs) of ∼0.1 to 14 M yr . The analysis of various line diagnostic diagrams reveals that ∼60% of compact emission-line galaxies have velocity widths, excitations, Hβ luminosities, SFRs, and mass-to-light ratios characteristic of young star-forming H II galaxies. The remaining 40% form a more heterogeneous class of evolved starbursts, similar to local starburst disk galaxies. We find that, although the compact galaxies at z > 0.7 have similar SFRs per unit mass to those at z < 0.7, they are on average ∼10 times more massive. Our sample implies a lower limit for the global comoving SFR density of ∼0.004 M yr Mpc at z = 0.55, and ∼0.008 M yr Mpc at z = 0.85 (assuming Salpeter IMF, H = 50 km s Mpc , and q = 0.5). These values, when compared to estimates for a sample of local compact galaxies selected in a similar fashion, support a history of the universe in which the SFR density declines by a factor ∼10 from z = 1 to today. From the comparison with the SFR densities derived for magnitude-limited samples of field galaxies, we conclude that compact emission-line galaxies, though only ∼20% of the general field population, may contribute as much as ∼45% to the global SFR of the universe at 0.4 < z < 1. © 1997. The American Astronomical Society. All rights reserved. 814 1/2 I814 ⊙ ⊙ ⊙ 0 o -2 -1 -1 -1 -1 -3 -1 -3 -1 -1

Keck Spectroscopy Of Redshift Z ∼ 3 Galaxies In The Hubble Deep Field, James Lowenthal, David C. Koo, Rafael Guzmán, Jesús Gallego, Andrew C. Phillips, S. M. Faber, Nicole P. Vogt, Garth D. Illingworth, Caryl Gronwall

Astronomy: Faculty Publications

We have obtained spectra with the 10 m Keck telescope of a sample of 24 galaxies having colors consistent with star-forming galaxies at redshifts 2 ≲ z ≲ 4.5 in the Hubble deep field (HDF). Eleven of these galaxies are confirmed to be at high redshift (z = 3.0), one is at z = 0.5, and the other 12 have uncertain redshifts but have spectra consistent with their being at z > 2. The spectra of the confirmed high-redshift galaxies show a diversity of features, including weak Lyα emission, strong Lyα breaks or damped Lyα absorption profiles, and the stellar and …

The Nature Of Compact Galaxies In The Hubble Deep Field. I. Global Properties, Andrew C. Phillips, Rafael Guzmán, Jesús Gallego, David C. Koo, James D. Lowenthal, Nicole P. Vogt, S. M. Faber, Garth D. Illingworth

Astronomy: Faculty Publications

We present 10 m Keck spectroscopy and photometry for a sample of 61 small (r1/2 ≤ 0″.5), faint (I814 ≤ 23.74), high-surface brightness (μI814 < 22.2 mag arcsec-2) galaxies in fields flanking the Hubble Deep Field. The majority of this empirically defined sample of compact galaxies lies at redshifts 0.4 ≲ z ≲ 1 (88% completeness in redshift identifications), ruling out a large component of low-redshift galaxies. The number of such galaxies in the range 1.4 ≲ z ≲ 2.2 is also constrained to ≲ 10%. The majority of the observed galaxies are emission-line systems, while a significant fraction (23%-34%) appear to be normal ellipticals or otherwise early-type systems. One object is an active galactic nucleus, and two are at high redshift (z > 2). The Keck redshift and photometric data are combined with Hubble Space Telescope images to derive luminosities and physical sizes. We also use emission-line widths, where available, to estimate masses. About two-thirds of the emission-line galaxies, or roughly one-half the sample, are small, low-mass, relatively luminous systems with properties resembling those of local H II galaxies. We compare the properties and numbers of these galaxies to the "bursting dwarf" model of Babul & Ferguson. Our sample …

A Group Of Galaxies At Redshift 2.38, Paul J. Francis, Bruce E. Woodgate, Stephen J. Warren, Palle Møller, Margaret Mazzolini, Andrew J. Bunker, James D. Lowenthal, Ted B. Williams, Takeo Minezaki, Yukiyasu Kobayashi, Yuzuru Yoshii

Astronomy: Faculty Publications

We report the discovery of a group of galaxies at redshift 2.38. We imaged ∼ 10% of a claimed supercluster of QSO absorption lines at z = 2.38. In this small field (2′ radius), we detect two Lyα-emitting galaxies. The discovery of two such galaxies in our tiny field supports Francis & Hewett's interpretation of the absorption-line supercluster as a high-redshift Great Wall. One of the Lyα galaxies lies 22″ from a background QSO and may be associated with a multicomponent Lyα absorption complex seen in the QSO spectrum. This galaxy has an extended (∼50 kpc), lumpy Lyα morphology surrounding …

The Lyman Continuum In Starburst Galaxies Observed With The Hopkins Ultraviolet Telescope, Claus Leitherer, Henry C. Ferguson, Timothy M. Heckman, James D. Lowenthal

Astronomy: Faculty Publications

The starburst galaxies IRAS 08339+6517, Mrk 1267, Mrk 66, and Mrk 496 (=NGC 6090) were observed with the Hopkins Ultraviolet Telescope (HUT) during the Astro-2 mission. All four galaxies have radial velocities larger than 5000 km s-1, permitting the measurement of their intrinsic Lyman continuum fluxes redward of the H I absorption edge in our Galaxy. The sample was selected on the basis of having the most favorable conditions for the escape of Lyman continuum photons. Two a upper limits of Fk < 7 X 10-16 ergs s-1 cm-2 A-1 were obtained for the flux around 900 A within the rest frame of each galaxy.A set of theoretical spectral energy distributions has been calculated. We show that there exists a tight correlation between the continuum luminosity at 900 A and the total number of photons emitted in the Lyman continuum, which is valid for high- and low-metallicity galaxies and essentially all relevant initial mass functions and star formation histories. Comparison with the observed values suggests that, on average, less than 3% of the intrinsic Lyman continuum photons escape from the program galaxies. Models for the ionization of the intergalactic medium at high 2 by young starbursts require a significant fraction of the ionizing radiation to escape from the galaxy. If the four galaxies observed by us have properties similar to young galaxies at redshift 2 2 3, such galaxies are not likely to provide Lyman continuum photons for the ionization of the early universe.

Imaging And Spectroscopy Of Damped Lyα Quasi-Stellar Object Absorption-Line Clouds, James Lowenthal, Craig J. Hogan, Richard F. Green, Bruce Woodgate, Adeline Caulet, Larry Brown, Jill Bechtold

Astronomy: Faculty Publications

We present the results of a multifaceted search for line emission from the vicinities of high-redshift quasi-stellar object (QSO) absorption-line clouds, most of them damped Lyα systems at z ≳ 2. Seven fields containing QSOs with known intervening damped Lyα absorbers were imaged with the GSFC Fabry-Perot Imager to search for diffuse redshifted Lyα. Apart from the one Lyα companion galaxy reported previously, no confirmed extended Lyα emission was detected down to 3 σ flux levels of around 3 x 10-17 ergs s-1 cm-2, corresponding to star formation rates ≲1 M⊙ yr-1, assuming case B recombination, a reasonable initial mass …

Imaging The Host Galaxies Of High-Redshift Radio-Quiet Qsos, James D. Lowenthal, Timothy M. Heckman, Matthew D. Lehnert, J. H. Elias

Astronomy: Faculty Publications

We present new deep K-band and optical images of four radio-quiet QSOs at z ≈ 1 and six radio-quiet QSOs at z ≈ 2.5, as well as optical images only of six more at z ≈ 2.5. We have examined the images carefully for evidence of extended "fuzz" from any putative QSO host galaxy. None of the z ≈ 2.5 QSOs shows any extended emission, and only two of the z ≈ 1 QSOs show marginal evidence for extended emission. Our 3 σ detection limits in the K images, mK ≃ 21 for an isolated source, would correspond approximately to …

Three-Dimensional Fabry-Perot Imaging Spectroscopy Of The Crab Nebula, Cassiopeia A, And Nova Gk Persei, Stephen S. Lawrence, Gordon M. Macalpine, Alan Uomoto, Bruce E. Woodgate, Larry W. Brown, Ronald J. Oliversen, James D. Lowenthal, Charles Liu

Astronomy: Faculty Publications

Three-dimensional spatial models of the line-emitting gas in the Crab Nebula, Cassiopeia A, and the nova remnant of GK Persei have been developed from imaging spectroscopy taken with the Goddard Fabry-Perot Imager mounted on the McGraw-Hill 1.3 m and Hiltner 2.4 m telescopes of the Michigan-Dartmouth-MIT Observatory. The spatial model of the Crab Nebula in [O III] λ5007 emission reveals the thin, annular morphology of the "high-helium torus," the association of this torus and other bright filament loops with north-south bipolar asymmetry of the remnant shell, the structure of the filamentary shell at the boundary with the inner synchrotron cavity, …

Extraordinary Line-Emitting Knots In The Crab Nebula, Gordon M. Macalpine, Stephen S. Lawrence, Beth A. Brown, Alan Uomoto, Bruce E. Woodgate, Larry W. Brown, Ronald J. Oliversen, James D. Lowenthal, Charles Liu

Astronomy: Faculty Publications

Extraordinary, semistellar, line-emitting knots are apparent in images of the Crab Nebula which were obtained with the Goddard Fabry-Perot imager at the Michigan-Dartmouth-MIT Observatory. The knots are most prominent for [O III] λ5007 emission through a 5.3 Å (FWHM) bandpass centered at 5015.3 Å, with representative fluxes of roughly 10-14 ergs cm-2 s-1. They are aligned in arcs, seven to the north and four to the south, from the pulsar. The northern group appears to be in a bounded corridor through the filamentary structure. Measurements over a 2 year baseline yield proper motions of order 0″.1 yr-1, corresponding to transverse …

Microjansky Source Counts And Spectral Indices At 8.44 Ghz, Rogier A. Windhorst, Edward B. Fomalont, R. Bruce Partridge, James D. Lowenthal

Astronomy: Faculty Publications

We used the VLA to make deep images of two 7′ × 7′ fields at 8.44 GHz with 10″ resolution. With an rms noise of 3.2 and 5.1 μJy, respectively, in the two fields, we compiled a catalog of 82 sources. From the complete sample of 20 sources with S ≥ 14.5 μJy, the differential 8.44 GHz source count is dN(S)/ dS = (-4.6 ± 0.7) × S-2.3 ± 0.2 Jy-1 sr-1 in the range 14.5-1000 mJy. Analysis of statistical image fluctuations from weak sources (Fomalont et al. 1993) suggests that this slope remains unchanged at γ = 2.3 ± …

Limits To Cosmic Background Radiation Fluctuations At 8.44 Ghz Between Angular Scales 10″ And 200″, Edward B. Fomalont, R. Bruce Partridge, James D. Lowenthal, Rogier A. Windhorst

Astronomy: Faculty Publications

We have used the VLA at 8.44 GHz to measure fluctuations in the cosmic background radiation (CBR) from two deep images, each 7′ x 7′ in size. No fluctuations between the angular scales 10″ and 200″ were detected. The most accurate limit (95% confidence) is ΔT/TCBR < 1.9 x 10-5 for 80″ resolution. For random Gaussian fluctuations with coherence angle θc, the limits are ΔT/TCBR < 30 x 10-5 for 22″ < θc < 60″. Outside this range the limits increase to ΔT/TCBR < 5 x 10-5 at θc = 12″ or 100″ and ΔT/TCBR < 10 x 10-5 at θc = 5″ or 120″. Similar limits have been obtained for the circularly and linearly polarized components of the CBR fluctuations. These limits were derived from the residual fluctuations in the images after (1) removing brighter foreground sources (> 14.5 μJy) which covered about 10% of each image; (2) estimating fluctuations of weaker sources by extrapolating the count of dN/dS = 4.6S-2.3 Jy-1 sr-1 to 4 μJy; and (3) determining fluctuations from receiver noise and instrumental errors by comparing the image variances from two independent halves of the data set. All analysis was …

An Interacting Galaxy Pair In The Bootes Void, D. Weistrop, P. Hintzen, R. C. Kennicut, C. Liu, James Lowenthal, K. P. Cheng, R. Oliversen, B. Woodgate

Astronomy: Faculty Publications

We report the first identified pair of interacting galaxies in the Bootes void. The galaxies, CG 692 (IRAS 1519 + 5050) and CG 693, have redshifts 0.0572 and 0.0575, respectively, and a mutual separation of ∼34 kpc. CG 692 is experiencing widespread star formation, at a rate estimated to be 18.4 M ⊙ yr-1. CG 693 is a Seyfert 1, the third AGN found in the Bootes void, with a small amount of extranuclear star formation. The pair is another example of interacting galaxies displaying starburst and Seyfert activity apparently triggered by the interaction.

Fabry-Perot Images Of Ngc 1275 And Its Puzzling High-Velocity System, Adeline Caulet, Bruce E. Woodgate, Larry W. Brown, Theodore R. Gull, Paul Hintzen, James D. Lowenthal, Ronald J. Oliversen, Michael M. Ziegler

Astronomy: Faculty Publications

We report the first images obtained with the Goddard Fabry-Perot imager, a very sensitive and tunable imaging system designed to achieve the high levels of performance required in the optical studies of faint emission-line extragalactic objects. A velocity sequence of calibrated narrow-band CCD images (FWHM ∼7 Å) has been obtained to cover the 3000 km s-1 velocity space between the redshifted Hα emission lines of NGC 1275 (the central dominant galaxy of the Perseus Cluster), its extended associated system of low-velocity (LV) filaments and the high-velocity (HV) system of knots, projected on the same line of sight in the sky. …