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Gary D. Schmidt,
Paula Szkody,
Karen M. Vanlandingham,
Scott F. Anderson,
J. C. Barentine,
Howard J. Brewington,
Patrick B. Hall,
Michael Harvanek,
S. J. Kleinman,
Jurek Krzesinski,
Dan Long,
Bruce Margon,
Eric H. Neilsen,
Jr, Peter R. Newman,
Atsuko Nitta,
Donald P. Schneider,
and Stephanie A. Snedden
[show abstract]
[hide abstract]
ABSTRACT: Discoveries of two new white dwarf plus M star binaries with striking optical cyclotron emission features from the Sloan Digital Sky Survey (SDSS) brings to six the total number of X-ray-faint, magnetic accretion binaries that accrete at rates 10-13 M☉ yr-1, or <1% of the values normally encountered in cataclysmic variables. This fact, coupled with donor stars that underfill their Roche lobes and very cool white dwarfs, brand the binaries as post-common-envelope systems whose orbits have not yet decayed to the point of Roche lobe contact. They are premagnetic cataclysmic variables, or pre-Polars. The systems exhibit spin-orbit synchronism and apparently accrete by efficient capture of the stellar wind from the secondary star, a process that has been dubbed a "magnetic siphon." Because of this, period evolution of the binaries will occur solely by gravitational radiation, which is very slow for periods >3 hr. Optical surveys for the cyclotron harmonics appear to be the only means of discovery, so the space density of pre-Polars could rival that of Polars, and the binaries provide an important channel of progenitors (in addition to the asynchronous intermediate Polars). Both physical and SDSS observational selection effects are identified that may help to explain the clumping of all six systems in a narrow range of magnetic field strength around 60 MG.
The Astrophysical Journal 12/2008; 630(2):1037. · 6.02 Impact Factor
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Daniel B. Zucker,
Alexei Y. Kniazev,
Eric F. Bell,
David Martínez-Delgado,
Eva K. Grebel,
Hans-Walter Rix,
Constance M. Rockosi,
Jon A. Holtzman,
Rene A. M. Walterbos,
James Annis, [......],
J. Brinkmann,
Howard Brewington,
Michael Harvanek,
Greg Hennessy,
S. J. Kleinman,
Jurek Krzesinski,
Dan Long, Peter R. Newman,
Atsuko Nitta,
and Stephanie A. Snedden
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of a new dwarf spheroidal satellite of M31, Andromeda IX, based on resolved stellar photometry from the Sloan Digital Sky Survey (SDSS). Using both SDSS and public archival data, we have estimated its distance and other physical properties, and compared these to the properties of a previously known dwarf spheroidal companion, Andromeda V, also observed by SDSS. Andromeda IX is the lowest surface brightness galaxy found to date (μV, 0 ~ 26.8 mag arcsec-2), and at the distance we estimate from the position of the tip of Andromeda IX's red giant branch, (m - M)0 ~ 24.5 (805 kpc), Andromeda IX would also be the faintest galaxy known (MV ~ -8.3).
The Astrophysical Journal 12/2008; 612(2):L121. · 6.02 Impact Factor
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Evalyn Gates,
Geza Gyuk,
Hugh C. Harris,
Mark Subbarao,
Scott Anderson,
S. J. Kleinman,
James Liebert,
Howard Brewington,
J. Brinkmann,
Michael Harvanek,
Jurek Krzesinski,
Don Q. Lamb,
Dan Long,
Eric H. Neilsen,
Jr, Peter R. Newman,
Atsuko Nitta,
and Stephanie A. Snedden
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of five new white dwarfs in the Sloan Digital Sky Survey. Four are ultracool, exhibiting strong collision-induced absorption (CIA) from molecular hydrogen and are similar in color to the three previously known coolest white dwarfs, SDSS J1337+00, LHS 3250, and LHS 1402. The fifth star shows milder CIA flux suppression and has a color and spectral shape similar to WD 0346+246. All five new white dwarfs are faint (g > 18.9) and have significant proper motions. One of the new ultracool white dwarfs, SDSS J0947, appears to be in a binary system with a slightly warmer (Teff ~ 5000 K) white dwarf companion.
The Astrophysical Journal 12/2008; 612(2):L129. · 6.02 Impact Factor
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Brian C. Lee,
Douglas L. Tucker,
Daniel E. Vanden Berk,
Brian Yanny,
Daniel E. Reichart,
Jennifer Adelman,
Bing Chen,
Mike Harvanek,
Arne Henden,
Željko Ivezić, [......],
Steph Snedden,
Don York,
John W. Briggs,
J. Brinkmann,
Istvan Csabai,
Greg S. Hennessy,
Stephen Kent,
Robert Lupton,
Heidi Jo Newberg,
and Chris Stoughton
[show abstract]
[hide abstract]
ABSTRACT: The discovery of an optical counterpart to GRB 010222 (detected by BeppoSAX) was announced 4.4 hr after the burst by Henden. The Sloan Digital Sky Survey's 0.5 m photometric telescope (PT) and 2.5 m survey telescope were used to observe the afterglow of GRB 010222 starting 4.8 hr after the gamma-ray burst. The 0.5 m PT observed the afterglow in five 300 s g*-band exposures over the course of half an hour, measuring a temporal decay rate in this short period of Fν t-1.0±0.5. The 2.5 m camera imaged the counterpart nearly simultaneously in five filters (u*, g*, r*, i*, z*), with r* = 18.74 ± 0.02 at 12:10 UT. These multicolor observations, corrected for reddening and the afterglow's temporal decay, are well-fitted by the power law Fν ν-0.90±0.03 with the exception of the u*-band UV flux which is 20% below this slope. We examine possible interpretations of this spectral shape, including source extinction in a star-forming region.
The Astrophysical Journal 12/2008; 561(1):183. · 6.02 Impact Factor
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Gary D. Schmidt,
Hugh C. Harris,
James Liebert,
Daniel J. Eisenstein,
Scott F. Anderson,
J. Brinkmann,
Patrick B. Hall,
Michael Harvanek,
Suzanne Hawley,
S. J. Kleinman, [......],
Eric H. Neilsen, Peter R. Newman,
Atsuko Nitta,
David J. Schlegel,
Donald P. Schneider,
Nicole M. Silvestri,
J. Allyn Smith,
Stephanie A. Snedden,
Paula Szkody,
and Dan Vanden Berk
[show abstract]
[hide abstract]
ABSTRACT: Beyond its goals related to the extragalactic universe, the Sloan Digital Sky Survey (SDSS) is an effective tool for identifying stellar objects with unusual spectral energy distributions. Here we report on the 53 new magnetic white dwarfs discovered during the first two years of the survey, including 38 whose data are made public in the 1500 deg2 First Data Release. Discoveries span the magnitude range 16.3 ≤ g ≤ 20.5, and based on the recovery rate for previously known magnetic white dwarfs, the completeness of the SDSS appears to be high for reasonably hot stars with B 3 MG and g 15. The new objects nearly double the total number of known magnetic white dwarfs and include examples with polar field strengths Bp > 500 MG, as well as several with exotic atmospheric compositions. The improved sample statistics and uniformity indicate that the distribution of magnetic white dwarfs has a broad peak in the range ~5-30 MG and a tail extending to nearly 109 G. Degenerates with polar fields Bp 50 MG are consistent with being descendents of magnetic Ap/Bp main-sequence stars, but low- and moderate-field magnetic white dwarfs appear to imply another origin. Yet-undetected magnetic F-type stars with convective envelopes that destroy the ordered underlying field are attractive candidates.
The Astrophysical Journal 12/2008; 595(2):1101. · 6.02 Impact Factor
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Daniel B. Zucker,
Alexei Y. Kniazev,
Eric F. Bell,
David Martínez-Delgado,
Eva K. Grebel,
Hans-Walter Rix,
Constance M. Rockosi,
Jon A. Holtzman,
Rene A. M. Walterbos,
Željko Ivezić,
J. Brinkmann,
Howard Brewington,
Michael Harvanek,
S. J. Kleinman,
Jurek Krzesinski,
Don Q. Lamb,
Dan Long, Peter R. Newman,
Atsuko Nitta,
and Stephanie A. Snedden
[show abstract]
[hide abstract]
ABSTRACT: The Sloan Digital Sky Survey has revealed an overdensity of luminous red giant stars ~3° (40 projected kpc) to the northeast of M31, which we have called Andromeda NE. The line-of-sight distance to Andromeda NE is within ~50 kpc of M31; Andromeda NE is not a physically unrelated projection. Andromeda NE has a g-band absolute magnitude of ~-11.6 and a central surface brightness of ~29 mag arcsec-2, making it nearly 2 orders of magnitude more diffuse than any known Local Group dwarf galaxy at that luminosity. Based on its distance and morphology, Andromeda NE is likely undergoing tidal disruption. Andromeda NE's red giant branch color is unlike that of M31's present-day outer disk or the stellar stream reported by Ibata et al., arguing against a direct link between Andromeda NE and these structures. However, Andromeda NE has a red giant branch color similar to that of the G1 clump; it is possible that these structures are both material torn off of M31's disk in the distant past or that these are both part of one ancient stellar stream.
The Astrophysical Journal 12/2008; 612(2):L117. · 6.02 Impact Factor
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Sean N. Raymond,
Gajus Miknaitis,
Oliver J. Fraser,
Arti Garg,
Suzanne L. Hawley,
Robert Jedicke,
Thomas Quinn,
Constance M. Rockosi,
Christopher W. Stubbs,
Scott F. Anderson, [......],
Howard Brewington,
J. Brinkmann,
Michael Harvanek,
Scot J. Kleinman,
Jurek Krzesiński,
Dan Long,
Eric H. Neilsen, Peter R. Newman,
Atsuko Nitta,
and Stephanie A. Snedden
[show abstract]
[hide abstract]
ABSTRACT: We present a detailed observational strategy for finding near-Earth objects (NEOs) with the Sloan Digital Sky Survey (SDSS) telescope. We investigate strategies in normal, unbinned mode, as well as binning the CCDs 2 × 2 or 3 × 3, which affects the sky coverage rate and the limiting apparent magnitude. We present results from 1 month, 3 year, and 10 year simulations of such surveys. For each cadence and binning mode, we evaluate the possibility of achieving the Spaceguard goal of detecting 90% of 1 km NEOs (absolute magnitude H ≤ 18 for an albedo of 0.1). We find that an unbinned survey is most effective at detecting H ≤ 20 NEOs in our sample. However, a 3 × 3 binned survey reaches the Spaceguard goal after only 7 years of operation. As the proposed large survey telescopes (Pan-STARRS, LSST) are at least 5–10 years from operation, an SDSS NEO survey could make a significant contribution to the detection and photometric characterization of the NEO population.
The Astronomical Journal 12/2007; 127(5):2978. · 4.03 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present 88 Hα profiles for 24 pulsating variable stars with periods between 1 and 3 days in order to explore the behavior of this line in type II as compared with classical Cepheids. Surprisingly, large velocity differences were found between Hα and the metal lines in some type II Cepheids. Strong emission was observed in three stars, VZ Aql, NW Lyr, and V439 Oph, while line filling by incipient emission is present in seven others. All of the stars with emission and most with incipient emission belong to Diethelm's AHB2 class, and the emission is associated with the secondary bump on the rising branch of the light curve. Two stars, BF Ser and MQ Aql, show doubling of the core near maximum light, and asymmetry of the line is noted in some spectra.
The Astronomical Journal 12/2007; 126(2):906. · 4.03 Impact Factor
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Suzanne L. Hawley,
Kevin R. Covey,
Gillian R. Knapp,
David A. Golimowski,
Xiaohui Fan,
Scott F. Anderson,
James E. Gunn,
Hugh C. Harris,
Željko Ivezić,
Gary M. Long, [......],
Michael Harvanek,
Gregory S. Hennessy,
S. J. Kleinman,
Jurek Krzesinski,
Dan Long,
Eric H. Neilsen, Peter R. Newman,
Atsuko Nitta,
Stephanie A. Snedden,
and Donald G. York
[show abstract]
[hide abstract]
ABSTRACT: An extensive sample of M, L, and T dwarfs identified in the Sloan Digital Sky Survey (SDSS) has been compiled. The sample of 718 dwarfs includes 677 new objects (629 M dwarfs and 48 L dwarfs), together with 41 that have been previously published. All new objects and some of the previously published ones have new optical spectra obtained either with the SDSS spectrographs or with the Apache Point Observatory 3.5 m ARC telescope. Spectral types and SDSS colors are available for all objects; approximately 35% also have near-infrared magnitudes measured by 2MASS (Two Micron All Sky Survey) or on the Mauna Kea system. We use this sample to characterize the color–spectral type and color-color relations of late-type dwarfs in the SDSS filters and to derive spectroscopic and photometric parallax relations for use in future studies of the luminosity and mass functions based on SDSS data. We find that the i* - z* and i* - J colors provide good spectral type and absolute magnitude (Mi*) estimates for M and L dwarfs. Our distance estimates for the current sample indicate that SDSS is finding early M dwarfs out to ~1.5 kpc, L dwarfs to ~100 pc, and T dwarfs to ~20 pc. The T dwarf photometric data show large scatter and are therefore less reliable for spectral type and distance estimation.
The Astronomical Journal 12/2007; 123(6):3409. · 4.03 Impact Factor
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Naohisa Inada,
Robert H. Becker,
Scott Burles,
Francisco J. Castander,
Daniel Eisenstein,
Patrick B. Hall,
David E. Johnston,
Bartosz Pindor,
Gordon T. Richards,
Paul L. Schechter, [......],
S. J. Kleinman,
Jurek Krzesiński,
Daniel C. Long,
Eric H. Neilsen,
Jr, Peter R. Newman,
Atsuko Nitta,
Donald P. Schneider,
S. Snedden,
and Donald G. York
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of a new gravitationally lensed quasar from the Sloan Digital Sky Survey, SDSS J092455.87+021924.9 (SDSS J0924+0219). This object was selected from among known SDSS quasars by an algorithm that was designed to select another known SDSS lensed quasar (SDSS J1226-0006A,B). Five separate components, three of which are unresolved, are identified in photometric follow-up observations obtained with the Magellan Consortium's 6.5 m Walter Baade Telescope at Las Campanas Observatory. Two of the unresolved components (designated A and B) are confirmed to be quasars with z = 1.524; the velocity difference is less than 100 km s-1 according to spectra taken with the W. M. Keck Observatory's Keck II Telescope at Mauna Kea, Hawaii. A third stellar component, designated C, has the colors of a quasar with redshift similar to components A and B. The maximum separation of the point sources is 178. The other two sources, designated G and D, are resolved. Component G appears to be the best candidate for the lensing galaxy. Although component D is near the expected position of the fourth lensed component in a four-image lens system, its properties are not consistent with being the image of a quasar at z ~ 1.5. Nevertheless, the identical redshifts of components A and B and the presence of component C strongly suggest that this object is a gravitational lens. Our observations support the idea that a foreground object reddens the fourth lensed component and that another unmodeled effect (such as micro- or millilensing) demagnifies it, but we cannot rule out the possibility that SDSS J0924+0219 is an example of the relatively rare class of "three-component" lens systems.
The Astronomical Journal 12/2007; 126(2):666. · 4.03 Impact Factor
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Bart Pindor,
Daniel J. Eisenstein,
Michael D. Gregg,
Robert H. Becker,
Naohisa Inada,
Masamune Oguri,
Patrick B. Hall,
David E. Johnston,
Gordon T. Richards,
Donald P. Schneider, [......],
Michael Harvanek,
S. J. Kleinman,
Jurek Krzesinski,
Dan Long,
Eric H. Neilsen,
Jr, Peter R. Newman,
Atsuko Nitta,
Stephanie A. Snedden,
and Donald G. York
[show abstract]
[hide abstract]
ABSTRACT: We report follow-up observations of two gravitational lens candidates identified in the Sloan Digital Sky Survey (SDSS) data set. We have confirmed that SDSS J102111.02+491330.4 is a previously unknown gravitationally lensed quasar. This lens system exhibits two images of a z = 1.72 quasar, with an image separation of 114 ± 004. Optical and near-IR imaging of the system reveals the presence of the lensing galaxy between the two quasar images. Observations of SDSS J112012.12+671116.0 indicate that it is more likely a binary quasar than a gravitational lens. This system has two quasars at a redshift of z = 1.49, with an angular separation of 149 ± 002. However, the two quasars have markedly different spectral energy distributions, and no lens galaxy is apparent in optical and near-IR images of this system. We also present a list of 31 SDSS lens candidates that follow-up observations have confirmed are not gravitational lenses.
The Astronomical Journal 12/2007; 131(1):41. · 4.03 Impact Factor
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James E. Gunn,
Walter A. Siegmund,
Edward J. Mannery,
Russell E. Owen,
Charles L. Hull,
R. French Leger,
Larry N. Carey,
Gillian R. Knapp,
Donald G. York,
William N. Boroski, [......], Peter R. Newman,
Atsuko Nitta,
John Peoples,
Jeffrey R. Pier,
Peter S. Prieto,
Angela Prosapio,
Claudio Rivetta,
Donald P. Schneider,
Stephanie Snedden,
and Shu-i Wang
[show abstract]
[hide abstract]
ABSTRACT: We describe the design, construction, and performance of the Sloan Digital Sky Survey telescope located at Apache Point Observatory. The telescope is a modified two-corrector Ritchey-Chrétien design with a 2.5 m, f/2.25 primary, a 1.08 m secondary, a Gascoigne astigmatism corrector, and one of a pair of interchangeable highly aspheric correctors near the focal plane, one for imaging and the other for spectroscopy. The final focal ratio is f/5. The telescope is instrumented by a wide-area, multiband CCD camera and a pair of fiber-fed double spectrographs. Novel features of the telescope include the following: (1) A 3° diameter (0.65 m) focal plane that has excellent image quality and small geometric distortions over a wide wavelength range (3000-10,600 Å) in the imaging mode, and good image quality combined with very small lateral and longitudinal color errors in the spectroscopic mode. The unusual requirement of very low distortion is set by the demands of time-delay-and-integrate (TDI) imaging. (2) Very high precision motion to support open-loop TDI observations. (3) A unique wind baffle/enclosure construction to maximize image quality and minimize construction costs. The telescope had first light in 1998 May and began regular survey operations in 2000.
The Astronomical Journal 12/2007; 131(4):2332. · 4.03 Impact Factor
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Douglas P. Finkbeiner,
Nikhil Padmanabhan,
David J. Schlegel,
Michael A. Carr,
James E. Gunn,
Constance M. Rockosi,
Maki Sekiguchi,
Robert H. Lupton,
G. R. Knapp,
Zeljko Ivezic, [......],
Max Tegmark,
Douglas L. Tucker,
Alan Uomoto,
Daniel E. Vanden Berk,
David H. Weinberg,
Andrew A. West,
Naoki Yasuda,
D. R. Yocum,
Donald G. York,
Idit Zehavi
[show abstract]
[hide abstract]
ABSTRACT: The Sloan Digital Sky Survey (SDSS) mosaic camera and telescope have obtained five-band optical-wavelength imaging near the Galactic plane outside of the nominal survey boundaries. These additional data were obtained during commissioning and subsequent testing of the SDSS observing system, and they provide unique wide-area imaging data in regions of high obscuration and star formation, including numerous young stellar objects, Herbig-Haro objects, and young star clusters. Because these data are outside the survey regions in the Galactic caps, they are not part of the standard SDSS data releases. This paper presents imaging data for 832 square degrees of sky (including repeats), in the star-forming regions of Orion, Taurus, and Cygnus. About 470 deg2 are now released to the public, with the remainder to follow at the time of SDSS Data Release 4. The public data in Orion include the star-forming region NGC 2068/NGC 2071/HH 24 and a large part of Barnard's loop.
The Astronomical Journal 12/2007; · 4.03 Impact Factor
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Gillian R. Knapp,
Christy A. Tremonti,
Constance M. Rockosi,
David J. Schlegel,
Brian Yanny,
Timothy C. Beers,
Carlos Allende Prieto,
Ron Wilhelm,
Robert H. Lupton,
James E. Gunn, [......],
Atsuko Nitta,
Michael Harvanek,
Jurek Krzesinski,
Howard J. Brewington,
John C. Barentine, Peter R. Newman,
Eric H. Nielsen,
Jr,
Masataka Fukugita,
and J. Brinkmann
[show abstract]
[hide abstract]
ABSTRACT: We describe the serendipitous discovery in the spectroscopic data of the Sloan Digital Sky Survey of a starlike object, SDSS J103913.70+533029.7, at a heliocentric radial velocity of +1012 km s-1. Its proximity in position and velocity to the spiral galaxy NGC 3310 suggests an association with the galaxy. At this distance, SDSS J103913.70+533029.7 has the luminosity of a super star cluster and a projected distance of 17 kpc from NGC 3310. Its spectroscopic and photometric properties imply a mass of >106 M and an age close to that of the tidal shells seen around NGC 3310, suggesting that it formed in the event that formed the shells.
The Astronomical Journal 12/2007; 131(2):859. · 4.03 Impact Factor
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Bart Pindor,
Daniel J. Eisenstein,
Michael D. Gregg,
Robert H. Becker,
Naohisa Inada,
Masamune Oguri,
Patrick B. Hall,
David E. Johnston,
Gordon T. Richards,
Donald P. Schneider, [......],
J. Brinkmann,
Michael Harvanek,
S. J. Kleinman,
Jurek Krzesinski,
Dan Long,
Neilsen, Jr., Eric H, Peter R. Newman,
Atsuko Nitta,
Stephanie A. Snedden,
Donald G. York
[show abstract]
[hide abstract]
ABSTRACT: We report follow-up observations of two gravitational lens candidates
identified in the Sloan Digital Sky Survey (SDSS) dataset. We have confirmed
that SDSS J102111.02+491330.4 is a previously unknown gravitationally lensed
quasar. This lens system exhibits two images of a $z = 1.72$ quasar, with an
image separation of $1{\farcs}14 \pm 0.04$. Optical and near-IR imaging of the
system reveals the presence of the lensing galaxy between the two quasar
images. Observations of SDSS J112012.12+671116.0 indicate that it is more
likely a binary quasar than a gravitational lens. This system has two quasars
at a redshift of $z = 1.49$, with an angular separation of $1{\farcs}49 \pm
0.02$. However, the two quasars have markedly different SEDs and no lens galaxy
is apparent in optical and near-IR images of this system. We also present a
list of 31 SDSS lens candidates which follow-up observations have confirmed are
\textit{not} gravitational lenses.
10/2005;
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Peter R. Newman,
Dan C. Long,
Stephanie A. Snedden,
S. J. Kleinman,
Atsuko Nitta,
Michael Harvanek,
Jurek Krzesinski,
Howard J. Brewington,
J. C. Barentine,
Eric H. Neilsen Jr,
David J. Schlegel,
for the SDSS Collaboration
[show abstract]
[hide abstract]
ABSTRACT: The Sloan Digital Sky Survey is the largest redshift survey conducted to
date, and the principal survey observations have all been conducted on the
dedicated SDSS 2.5m and 0.5m telescopes at Apache Point Observatory. While the
whole survey has many unique features, this article concentrates on a
description of the systems surrounding the dual fibre-input spectrographs that
obtain all the survey spectra and that are capable of recording 5,760
individual spectra per night on an industrial, consistent, mass-production
basis. It is hoped that the successes and lessons learned will prove
instructive for future large spectrographic surveys.
08/2004;
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Evalyn Gates,
Geza Gyuk,
Hugh C. Harris,
Mark Subbarao,
Scott Anderson,
S. J. Kleinman,
James Liebert,
Howard Brewington,
J. Brinkmann,
Michael Harvanek,
Jurek Krzesinski,
Don Q. Lamb,
Dan Long,
Neilsen, Jr., Eric H, Peter R. Newman,
Atsuko Nitta,
Stephanie A. Snedden
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of five very cool white dwarfs in the Sloan Digital
Sky Survey (SDSS). Four are ultracool, exhibiting strong collision induced
absorption (CIA) from molecular hydrogen and are similar in color to the three
previously known coolest white dwarfs, SDSS J1337+00, LHS 3250 and LHS 1402.
The fifth, an ultracool white dwarf candidate, shows milder CIA flux
suppression and has a color and spectral shape similar to WD 0346+246. All five
new white dwarfs are faint (g > 18.9) and have significant proper motions. One
of the new ultracool white dwarfs, SDSS J0947, appears to be in a binary system
with a slightly warmer (T_{eff} ~ 5000K) white dwarf companion.
05/2004;
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Tomotsugu Goto,
Robert C. Nichol,
Sadanori Okamura,
Maki Sekiguchi,
Christopher J. Miller,
Mariangela Bernardi,
Andrew Hopkins,
Christy Tremonti,
Andrew Connolly,
Francisco J. Castander, [......],
Zeljko Ivezic,
Scot J. Kleinman,
Jurek Krzesinski,
Dan Long,
Jon Loveday,
Eric H. Neilsen, Peter R. Newman,
Atsuko Nitta,
Stephanie A. Snedden,
Mark Subbarao
[show abstract]
[hide abstract]
ABSTRACT: We present here a new and homogeneous sample of 3340 galaxies selected
from the Sloan Digital Sky Survey (SDSS) based solely on the observed
strength of their Hδ hydrogen Balmer absorption line. The presence
of a strong Hδ line within the spectrum of a galaxy indicates that
the galaxy has undergone a significant change in its star-formation
history within the last Gigayear. Therefore, such galaxies have received
considerable attention in recent years, because they provide an
opportunity to study galaxy evolution in action. These galaxies are
commonly known as ``post-starburst'', ``E + A'', ``k + a'', and
Hδ-strong galaxies. Their study has been severely hampered by the
lack of a large, statistical sample of such galaxies. In this paper, we
rectify this problem by selecting a sample of galaxies which possess an
absorption Hδ equivalent width of EW(Hδmax) -
ΔEW(Hδmax) > 4Å from 106682 galaxies in
the SDSS. The measured abundance of our Hδ-strong (HDS) galaxies
is 2.6 ± 0.1% of all galaxies within a volume-limited sample of
0.05 < z < 0.1 and Mr* < -20.5, which is
consistent with previous studies of such galaxies described in the
literature. We find that only 25 of our HDS galaxies in this
volume-limited sample ( 3.5 ± 0.7% ) show no, or little, evidence
for [O II ] and Hα emission lines, thus indicating that true E + A
galaxies (as originally defined by Dressler and Gunn) are extremely rare
objects at low redshift, i.e., only 0.09 ± 0.02% of all galaxies
in this volume-limited sample are true E + A galaxies. In contrast, 89
± 5% of our HDS galaxies in the volume-limited sample have
significant detections of the [O II ] and Hα emission lines. Of
these, only 131 galaxies are robustly classified as Active Galactic
Nuclei (AGNs) and, therefore, a majority of these emission-line HDS
galaxies are star-forming galaxies. We find that 52 ± 12% (27/52)
of the galaxies in our volume-limited HDS sample that possess no
detectable [O II ] emission, do however possess detectable Hα
emission lines. These may be dusty star-forming galaxies. We provide the
community with this new catalog of Hδ-strong galaxies to aid in
our understanding of these galaxies, via detailed follow-up
observations, as well as providing a low-redshift sample for comparison
with higher redshift studies of HDS galaxies.
Publications- Astronomical Society of Japan 05/2003; 55:771-787. · 2.44 Impact Factor
-
Naohisa Inada,
Robert H. Becker,
Scott Burles,
Francisco J. Castander,
Daniel Eisenstein,
Patrick B. Hall,
David E. Johnston,
Bartosz Pindor,
Gordon T. Richards,
Paul L. Schechter, [......],
Joshua A. Frieman,
S. J. Kleinman,
Jurek Krzesi'nski,
Daniel C. Long,
Neilsen, Jr., Eric H, Peter R. Newman,
Atsuko Nitta,
Donald P. Schneider,
S. Snedden,
Donald G. York
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of a new gravitationally lensed quasar from the Sloan
Digital Sky Survey, SDSS J092455.87+021924.9 (SDSS J0924+0219). This object was
selected from among known SDSS quasars by an algorithm that was designed to
select another known SDSS lensed quasar (SDSS 1226-0006A,B). Five separate
components, three of which are unresolved, are identified in photometric
follow-up observations obtained with the Magellan Consortium's 6.5m Walter
Baade telescope at Las Campanas Observatory. Two of the unresolved components
(designated A and B) are confirmed to be quasars with z=1.524; the velocity
difference is less than 100 km sec^{-1} according to spectra taken with the W.
M. Keck Observatory's Keck II telescope on Mauna Kea. A third stellar
component, designated C, has the colors of a quasar with redshift similar to
components A and B. The maximum separation of the point sources is 1.78". The
other two sources, designated G and D, are resolved. Component G appears to be
the best candidate for the lensing galaxy. Although component D is near the
expected position of the fourth lensed component in a four image lens system,
its properties are not consistent with being the image of a quasar at z~1.5.
Nevertheless, the identical redshifts of components A and B and the presence of
component C strongly suggest that this object is a gravitational lens. Our
observations support the idea that a foreground object reddens the fourth
lensed component and that another unmodeled effect (such as micro- or
milli-lensing) demagnificates it, but we cannot rule out the possibility that
SDSS0924+0219 is an example of the relatively rare class of ``three component''
lens systems.
04/2003;
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Tomotsugu Goto,
Robert C. Nichol,
Christopher J. Miller,
Mariangela Bernardi,
Andrew Hopkins,
Christy Tremonti,
Andrew Connolly,
Francisco J. Castander,
J. Brinkmann,
Masataka Fukugita, [......],
Jurek Krzesinski,
Dan Long,
Jon Loveday,
Eric H. Neilsen, Peter R. Newman,
Atsuko Nitta,
Sadanori Okamura,
Maki Sekiguchi,
Stephanie A. Snedden,
Mark SubbaRao
[show abstract]
[hide abstract]
ABSTRACT: [Abridged] We present here a new and homogeneous sample of 3340 galaxies selected from the Sloan Digital Sky Survey (SDSS) based solely on the observed strength of their Hdelta absorption line. These galaxies are commonly known as ``post-starburst'' or ``E+A'' galaxies, and the study of these galaxies has been severely hampered by the lack of a large, statistical sample of such galaxies. In this paper, we rectify this problem by selecting a sample of galaxies which possess an absorption Hdelta equivalent width of EW(Hdelta_max) - Delta EW(Hdelta_max) > 4A from 106682 galaxies in the SDSS. We have performed extensive tests on our catalog including comparing different methodologies of measuring the Hdelta absorption and studying the effects of stellar absorption, dust extinction, emission-filling and measurement error. The measured abundance of our Hdelta-selected (HDS) galaxies is 2.6 +/- 0.1% of all galaxies within a volume-limited sample of 0.05<z<0.1 and M(r*)<-20.5, which is consistent with previous studies of such galaxies in the literature. We find that only 25 of our HDS galaxies in this volume-limited sample (3.5+/-0.7%) show no evidence for OII and Halpha emission, thus indicating that true E+A (or k+a) galaxies are extremely rare objects at low redshift, i.e., only 0.09+/-0.02% of all galaxies in this volume-limited sample are true E+A galaxies. In contrast, 89+/-5% of our HDS galaxies in the volume-limited sample have significant detections of the OII and Halpha emission lines. We find 27 galaxies in our volume-limited HDS sample that possess no detectable OII emission, but do however possess detectable Halpha emission. These galaxies may be dusty star-forming galaxies. We provide the community with this new catalog of Hdelta-selected galaxies to aid in the understanding of these galaxies.
02/2003;
