Physical Sciences and Mathematics | Open Access Articles

The Vlt Lbg Redshift Survey I: Clustering And Dynamics Of ≈ 1000 Galaxies At Z ≈ 3⋆, R. M. Bielby, T. Shanks, P. M. Weilbacher, L. Infante, N. H.M. Crighton, C. Bornancini, N. Bouché, P. Héraudeau, D. G. Lambas, James D. Lowenthal, D. Minniti, N. Padilla, P. Petitjean, T. Theuns

Astronomy: Faculty Publications

We present the initial imaging and spectroscopic data acquired as part of the Very Large Telescope (VLT) VIMOS Lyman-break galaxy Survey. UBR (or UBVI) imaging covers five ≈36 × 36 arcmin fields centred on bright z > 3 quasi-stellar objects (QSOs), allowing ≈210002 < z < 3.5 galaxy candidates to be selected using the Lyman-break technique. We performed spectroscopic follow-up using VLT VIMOS, measuring redshifts for 1020 z > 2 Lyman-break galaxies and 10 z > 2 QSOs from a total of 19 VIMOS pointings. From the galaxy spectra, we observe a 625 ± 510kms velocity offset between the interstellar absorption and Lyman α emission-line redshifts, consistent with previous results. Using the photometric and spectroscopic catalogues, we have analysed the galaxy clustering at z≈ 3. The angular correlation …

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Dynamics Of Lyman Break Galaxies And Their Host Halos, James D. Lowenthal, David C. Koo, Luc Simard, Eelco Van Kampen

Astronomy: Faculty Publications

We present deep two-dimensional spectra of 22 candidate and confirmed Lyman break galaxies (LBGs) at redshifts 2 < z < 4 in the Hubble Deep Field (HDF) obtained at the Keck II telescope. The targets were preferentially selected with spatial extent and/or multiple knot morphologies, and we used slitmasks and individual slits tilted to optimize measurement of any spatially resolved kinematics. Our sample is more than 1 mag fainter and is at higher redshift than the kinematic LBG targets previously studied by others. The median target magnitude was I814 = 25.3, and total exposure times ranged from 10 to 50 ks. We measure redshifts, some new, ranging from z = 0.2072 to z = 4.056, including two interlopers at z < 1, and resulting in a sample of 14 LBGs with a median redshift z = 2.424. The morphologies and kinematics of the close pairs and multiple knot sources in our sample are generally inconsistent with galaxy formation scenarios postulating that LBGs occur only at the bottom of the potential wells of massive host halos; rather, they support "collisional starburst" models with significant …

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The Aztec/Sma Interferometric Imaging Survey Of Submillimeter-Selected High-Redshift Galaxies, Joshua D. Younger, Giovanni G. Fazio, Jia Sheng Huang, Min S. Yun, Grant W. Wilson, Matthew L.N. Ashby, Mark A. Gurwell, Alison B. Peck, Glen R. Petitpas, David J. Wilner, David H. Hughes, Itziar Aretxaga, Sungeun Kim, Kimberly S. Scott, Jason Austermann, Thushara Perera, James D. Lowenthal

Astronomy: Faculty Publications

We present results from a continuing interferometric survey of high-redshift submillimeter galaxies (SMGs) with the Submillimeter Array, including high-resolution (beam size ∼ 2 arcsec) imaging of eight additional AzTEC 1.1 mm selected sources in the COSMOS field, for which we obtain six reliable (peak signal-to-noise ratio (S/N) >5 or peak S/N >4 with multiwavelength counterparts within the beam) and two moderate significance (peak S/N >4) detections. When combined with previous detections, this yields an unbiased sample of millimeter-selected SMGs with complete interferometric follow up. With this sample in hand, we (1) empirically confirm the radio-submillimeter association, (2) examine the submillimeter …

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SPitzer Irac Infrared Colours Of Submillimetre-Bright Galaxies, Min S. Yun, Itziar Aretxaga, Matthew L.N. Ashby, Jason Austermann, Giovanni G. Fazio, Mauro Giavalisco, Jia Sheng Huang, David H. Hughes, Sungeun Kim, James D. Lowenthal, Thushara Perera, Kim Scott, Grant Wilson, Joshua D. Younger

Astronomy: Faculty Publications

High-redshift submillimetre-bright galaxies identified by blank field surveys at millimetre and submillimetre wavelengths appear in the region of the Infra Red Array Camera (IRAC) colour-colour diagrams previously identified as the domain of luminous active galactic nuclei (AGNs). Our analysis using a set of empirical and theoretical dusty starburst spectral energy distribution (SED) models shows that power-law continuum sources associated with hot dust heated by young (≲100 Myr old), extreme starbursts at z > 2 also occupy the same general area as AGNs in the IRAC colour-colour plots. A detailed comparison of the IRAC colours and SEDs demonstrates that the two populations …

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Evidence For A Population Of High-Redshift Submillimeter Galaxies From Interferometric Imaging, Joshua D. Younger, Giovanni G. Fazio, Jia Sheng Huang, Min S. Yun, Grant W. Wilson, Matthew L.N. Ashby, Mark A. Gurwell, Kamson Lai, Alison B. Peck, Glen R. Petitpas, David J. Wilner, Daisuke Iono, Kotaro Kohno, Ryohei Kawabe, David H. Hughes, Itziar Aretxaga, Tracy Webb, Alejo Martínez-Sansigre, Sungeun Kim, Kimberly S. Scott, Jason Austermann, Thushara Perera, James Lowenthal, Eva Schinnerer, Vernesa Smolčić

Astronomy: Faculty Publications

We have used the Submillimeter Array to image a flux-limited sample of seven submillimeter galaxies, selected by the AzTEC camera on the JCMT at 1.1 mm, in the COSMOS field at 890 μm with ∼2″ resolution. All of the sources - two radio-bright and five radio-dim - are detected as single point sources at high significance (>6 σ), with positions accurate to ∼0.2″ that enable counterpart identification at other wavelengths observed with similarly high angular resolution. All seven have IRAC counterparts, but only two have secure counterparts in deep HST ACS imaging. As compared to the two radio-bright sources …

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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.

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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 …

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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

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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 …

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Full-Text Articles in Physical Sciences and Mathematics

The Vlt Lbg Redshift Survey I: Clustering And Dynamics Of ≈ 1000 Galaxies At Z ≈ 3⋆, R. M. Bielby, T. Shanks, P. M. Weilbacher, L. Infante, N. H.M. Crighton, C. Bornancini, N. Bouché, P. Héraudeau, D. G. Lambas, James D. Lowenthal, D. Minniti, N. Padilla, P. Petitjean, T. Theuns

Astronomy: Faculty Publications

Dynamics Of Lyman Break Galaxies And Their Host Halos, James D. Lowenthal, David C. Koo, Luc Simard, Eelco Van Kampen

Astronomy: Faculty Publications

Astronomy: Faculty Publications

SPitzer Irac Infrared Colours Of Submillimetre-Bright Galaxies, Min S. Yun, Itziar Aretxaga, Matthew L.N. Ashby, Jason Austermann, Giovanni G. Fazio, Mauro Giavalisco, Jia Sheng Huang, David H. Hughes, Sungeun Kim, James D. Lowenthal, Thushara Perera, Kim Scott, Grant Wilson, Joshua D. Younger

Astronomy: Faculty Publications

Astronomy: Faculty Publications

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

Astronomy: Faculty Publications

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

Astronomy: Faculty Publications

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