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T. R. Geballe,
G. R. Knapp,
S. K. Leggett,
X. Fan,
D. A. Golimowski,
S. Anderson,
J. Brinkmann,
I. Csabai,
J. E. Gunn,
S. L. Hawley, [......],
E. Peng, J. R. Pier,
C. M. Rockosi,
D. P. Schneider,
J. Allyn Smith,
M. A. Strauss,
Z. I. Tsvetanov,
A. Uomoto,
D. G. York,
and W. Zheng
[show abstract]
[hide abstract]
ABSTRACT: We present 0.6-2.5 μm, R 400 spectra of 27 cool, low-luminosity stars and substellar objects. Based on these and previously published spectra, we develop a preliminary spectral classification system for L and T dwarfs. For late L and T types the classification system is based entirely on four spectral indices in the 1-2.5 μm interval. Two of these indices are derived from water absorption bands at 1.15 and 1.4 μm, the latter of which shows a smooth increase in depth through the L and T sequences and can be used to classify both spectral types. The other two indices make use of methane absorption features in the H and K bands, with the K-band index also applicable to mid-to-late L dwarfs. Continuum indices shortward of 1 μm used by previous authors to classify L dwarfs are found to be useful only through mid-L subclasses. We employ the 1.5 μm water index and the 2.2 μm methane index to complete the L classification through L9.5 and to link the new system with a modified version of the 2MASS "color-d" index. By correlating the depths of the methane and water absorption features, we establish a T spectral sequence from T0 to T8, based on all four indices, that is a smooth continuation of the L sequence. We reclassify two 2MASS L8 dwarfs as L9 and L9.5 and identify one SDSS object as L9. In the proposed system methane absorption appears in the K band approximately at L8, two subclasses earlier than its appearance in the H band. The L and T spectral classes are distinguished by the absence and presence, respectively, of H-band methane absorption.
The Astrophysical Journal 12/2008; 564(1):466. · 6.02 Impact Factor
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D. P. Schneider,
P. B. Hall,
G. T. Richards,
M. A. Strauss,
D. E. vanden Berk,
S. F. Anderson,
W. N. Brandt,
X. Fan,
S. Jester,
J. Gray, [......],
J. Krzesinski,
D. C. Long,
R. H. Lupton,
A. Nitta, J. R. Pier,
D. H. Saxe,
Y. Shen,
S. A. Snedden,
D. H. Weinberg,
J. Wu
[show abstract]
[hide abstract]
ABSTRACT: The fourth edition of the Sloan Digital Sky Survey (SDSS) Quasar
Catalog, made from the SDSS Fifth Data Release, contains 77,429 objects;
this is an increase of over 30,000 entries since the previous edition
(Schneider et al., Cat. <VII/243>). The catalog consists of the
objects in the SDSS Fifth Data Release that have luminosities larger
than Mi=-22.0 (in a cosmology with Ho=70km.s-1.Mpc-1,
ΩM=0.3, and ΩΛ=0.7), have at
least one emission line with FWHM larger than 1000km.s-1 or have
interesting or complex absorption features, are fainter than i~15.0, and
have highly reliable redshifts. The area covered by the catalog is about
5740deg2. The quasar redshifts range from 0.08 to 5.41, with
a median value of 1.48; the catalog includes 891 quasars at redshifts
greater than 4, of which 36 are at redshifts greater than 5.
Approximately half of the catalog quasars have i<19; nearly all have
i<21. For each object the catalog presents positions accurate to
better than 0.2" rms per coordinate, five-band (ugriz) CCD-based
photometry with typical accuracy of 0.03mag, and information on the
morphology and selection method. The catalog also contains basic radio,
near-infrared, and X-ray emission properties of the quasars, when
available, from other large-area surveys. The calibrated digital spectra
cover the wavelength region 3800-9200Å at a spectral resolution of
about 2000; the spectra can be retrieved from the public database using
the information provided in the catalog. The average SDSS colors of
quasars as a function of redshift, derived from the catalog entries, are
presented in tabular form. Approximately 96% of the objects in the
catalog were discovered by the SDSS.
(1 data file).
VizieR Online Data Catalog. 04/2008; 7252.
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Z. Ivezic,
N. Bond,
M. Juric,
J. A. Munn,
R. H. Lupton, J. R. Pier,
G. S. Hennessy,
G. R. Knapp,
J. E. Gunn,
C. M. Rockosi,
T. Quinn
[show abstract]
[hide abstract]
ABSTRACT: We discuss several results made possible by accurate SDSS astrometric measurements in a large sky area, with emphasis on asteroids and stellar proper motions obtained by comparing POSS and SDSS. SDSS has observed over 200,000 moving objects in five photometric bands, corresponding to about two orders of magnitude increase over previous multi--color surveys. These data were used to extend the measurement of asteroid size distribution to a smaller size limit, to demonstrate that asteroid dynamical families, defined as clusters in orbital parameter space, also strongly segregate in color space, and to discover a correlation between asteroid age and colors. A preliminary analysis of SDSS-POSS proper motions for about 1 million M dwarf stars demonstrates that, in the 0.1-1 kpc distance range, the rotational velocity and its dispersion for disk stars increase with the distance from the Galactic plane.
02/2007;
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H. C. Harris,
B. Canzian,
C. C. Dahn,
H. H. Guetter,
A. A. Henden,
S. E. Levine,
C. B. Luginbuhl,
A. K. B. Monet,
D. G. Monet,
J. A. Munn, J. R. Pier,
R. C. Stone,
T. Tilleman,
F. J. Vrba,
R. L. Walker
[show abstract]
[hide abstract]
ABSTRACT: The accuracy of trigonometric parallaxes from the U.S. Naval Observatory
(USNO) has continued to improve. An optical CCD camera is used
regularly on the 61-inch telescope. It produces parallaxes with typical
errors of ±0.5 mas, and can reach ±0.3 mas with some
effort. The program provides distances, absolute magnitudes, and
tangential velocities accurate to a few percent for many white dwarfs
and low-luminosity red and brown dwarfs. Other classes of special
interest being observed are planetary nebulae, cataclysmic variables,
dwarf novae, and dwarf carbon stars. Some stars show residual
perturbations from a close companion, and the astrometric orbital
solutions indicate a brown dwarf or (in a few cases) a possible
planetary-mass companion. In addition, a near-IR InSb camera is used for
parallaxes of very red L and T brown dwarfs. We discuss the relationship
of USNO and other programs, and the prospects for further progress.
09/2005; 338:122.
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D. P. Schneider,
P. B. Hall,
G. T. Richards,
D. E. Vanden Berk,
S. F. Anderson,
X Fan,
S. Jester,
C. Stoughton,
M. A. Strauss,
M. Subbarao, [......],
A. Nitta, J. R. Pier,
C. M. Rockosi,
D. H. Saxe,
D. J. Schlegel,
S. A. Snedden,
A. S. Szalay,
A. R. Thakar,
A. Uomoto,
D. G. York
[show abstract]
[hide abstract]
ABSTRACT: We present the third edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 46,420 objects in the SDSS Third Data Release that have luminosities larger than M_i = -22 (in a cosmology with H_0 = 70 km/s/Mpc, Omega_M = 0.3, and Omega_Lambda = 0.7), have at least one emission line with FWHM larger than 1000 km/s or are unambiguously broad absorption line quasars, are fainter than i = 15.0, and have highly reliable redshifts. The area covered by the catalog is 4188 sq. deg. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.47; the high-redshift sample includes 520 quasars at redshifts greater than four, of which 17 are at redshifts greater than five. For each object the catalog presents positions accurate to better than 0.2 arcsec. rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800--9200A at a spectral resolution about 2000; the spectra can be retrieved from the public database using the information provided in the catalog. A total of 44,221 objects in the catalog were discovered by the SDSS; 28,400 of the SDSS discoveries are reported here for the first time.
04/2005;
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[show abstract]
[hide abstract]
ABSTRACT: We present a new estimate of the mass of the Milky Way, making use of a
large sample of 955 field horizontal-branch (FHB) stars from the Early
Data Release of the Sloan Digital Sky Survey. This sample of stars has
been classified on the basis of an automated analysis approach, in
combination with other methods, in order to obtain estimates of the
physical parameters of the stars, i.e., T_eff, log g, [Fe/H], and should
be relatively free of contamination from halo blue stragglers. The stars
all have measured radial velocities and photometric distance estimates,
and the sample includes objects as distant as ˜ 75 kpc from the
Galactic center. Application of a Bayesian likelihood method, for a
specific model of the Galaxy, indicates that the total mass of the
Galaxy lies in the range 1.5-4.0 x 1012 Msun.
Our sample appears to reveal a clear signature of a dual halo population
of FHB stars, with the boundary between the inner and outer halo around
20 kpc, and the possibility of rather striking differences in the
rotational properties of the Galaxy at low metallicity.
Proceedings of the International Astronomical Union 06/2004; 220:195.
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[show abstract]
[hide abstract]
ABSTRACT: Using wide-field photometric data from the Sloan Digital Sky Survey (SDSS) we recently showed that the Galactic globular cluster Palomar 5 is in the process of being tidally disrupted. Its tidal tails were initially detected in a 2.5 degree wide band along the celestial equator. A new analysis of SDSS data for a larger field now reveals that the tails of Pal 5 have a much larger spatial extent and can be traced over an arc of 10 deg across the sky, corresponding to a projected length of 4 kpc at the distance of the cluster. The number of former cluster stars found in the tails adds up to about 1.2 times the number of stars in the cluster. The radial profile of stellar surface density in the tails follows approximately a power law r^gamma with -1.5 < gamma < -1.2. The stream of debris from Pal 5 is significantly curved, which demonstrates its acceleration by the Galactic potential. The cluster is presently near the apocenter but has repeatedly undergone disk crossings in the inner part of the Galaxy leading to strong tidal shocks. Our results suggest that the observed debris originates mostly from mass loss within the last 2 Gyrs. The cluster is likely to be destroyed after the next disk crossing, which will happen in about 100 Myr. (abridged) Comment: 44 pages, including 14 figures (Figs.1,3 & 14 with decreased resolution), accepted for publication in the Astronomical Journal
07/2003;
-
H. C. Harris,
J. Liebert,
S. J. Kleinman,
A. Nitta,
S. F. Anderson,
G. R. Knapp,
J. Krzesinski,
G. Schmidt,
M. A. Strauss,
D. Vanden Berk, [......],
S. Kent,
D. Q. Lamb,
R. H. Lupton,
R. C. Nichol, J. R. Pier,
D. J. Schlegel,
M. Subbarao,
A. Uomoto,
B. Yanny,
D. G. York
[show abstract]
[hide abstract]
ABSTRACT: An initial assessment is made of white dwarf and hot subdwarf stars observed in the Sloan Digital Sky Survey. In a small area of sky (190 square degrees), observed much like the full survey will be, 269 white dwarfs and 56 hot subdwarfs are identified spectroscopically where only 44 white dwarfs and 5 hot subdwarfs were known previously. Most are ordinary DA (hydrogen atmosphere) and DB (helium) types. In addition, in the full survey to date, a number of WDs have been found with uncommon spectral types. Among these are blue DQ stars displaying lines of atomic carbon; red DQ stars showing molecular bands of C_2 with a wide variety of strengths; DZ stars where Ca and occasionally Mg, Na, and/or Fe lines are detected; and magnetic WDs with a wide range of magnetic field strengths in DA, DB, DQ, and (probably) DZ spectral types. Photometry alone allows identification of stars hotter than 12000 K, and the density of these stars for 15<g<20 is found to be ~2.2 deg^{-2} at Galactic latitudes 29-62 deg. Spectra are obtained for roughly half of these hot stars. The spectra show that, for 15<g<17, 40% of hot stars are WDs and the fraction of WDs rises to ~90% at g=20. The remainder are hot sdB and sdO stars. Comment: Accepted for AJ; 43 pages, including 12 figures and 5 tables
05/2003;
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H. C. Harris,
C. C. Dahn,
F. J. Vrba,
H. H. Guetter,
B. Canzian,
A. A. Henden,
S. E. Levine,
C. B. Luginbuhl,
A. K. B. Monet,
D. G. Monet, J. R. Pier,
R. C. Stone,
R. L. Walker
[show abstract]
[hide abstract]
ABSTRACT: Trigonometric parallaxes have been measured by Dahn et al. (2002) for 28 cool dwarfs and brown dwarfs, including 17 L dwarfs and three T dwarfs. Broadband CCD and near-IR photometry (VRIz*JHK) have been obtained for these objects and for 24 additional late-type dwarfs. These data have been supplemented with astrometry and photometry from the literature, including parallaxes for the brighter companions of ten L and two T dwarfs. The absolute magnitudes and colors are reviewed here. The I-J color and the spectral type are both good predictors of absolute magnitude for late-M and L dwarfs. M_J becomes monotonically fainter with I-J color and with spectral type through late-L dwarfs, then brightens for early-T dwarfs. In contrast, the J-K color correlates poorly with absolute magnitude for L dwarfs. Using several other parameters from the literature (Li detection, H-alpha emission strength, projected rotation velocity, and tangential velocity), we fail to uncover any measurable parameter that correlates with the anomalous J-K color.
08/2002;
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C. C. Dahn,
H. C. Harris,
F. J. Vrba,
H. H. Guetter,
B. Canzian,
A. A. Henden,
S. E. Levine,
C. B. Luginbuhl,
A. K. B. Monet,
D. G. Monet, J. R. Pier,
R. C. Stone,
R. L. Walker,
A. J. Burgasser,
J. E. Gizis,
J. D. Kirkpatrick,
J. Liebert,
I. N. Reid
[show abstract]
[hide abstract]
ABSTRACT: Trigonometric parallax determinations are presented for 28 late type dwarfs and brown dwarfs, including eight M dwarfs with spectral types between M7 and M9.5, 17 L dwarfs with spectral types between L0 and L8, and three T dwarfs. Broadband photometry at CCD wavelengths (VRIz) and/or near-IR wavelengths (JHK) are presented for these objects and for 24 additional late-type dwarfs. Supplemented with astrometry and photometry from the literature, including ten L and two T dwarfs with parallaxes established by association with bright, usually HIPPARCOS primaries, this material forms the basis for studying various color-color and color-absolute magnitude relations. The I-J color is a good predictor of absolute magnitude for late-M and L dwarfs. M_J becomes monotonically fainter with I-J color and with spectral type through late-L dwarfs, then brightens for early-T dwarfs. The combination of zJK colors alone can be used to classify late-M, early-L, and T dwarfs accurately, and to predict their absolute magnitudes, but is less effective at untangling the scatter among mid- and late-L dwarfs. The mean tangential velocity of these objects is found to be slightly less than that for dM stars in the solar neighborhood, consistent with a sample with a mean age of several Gyr. Using colors to estimate bolometric corrections, and models to estimate stellar radii, effective temperatures are derived. The latest L dwarfs are found to have T_eff ~ 1360 K. Comment: 48 pages, including 7 figures and 6 tables. Accepted for AJ
05/2002;
-
J A Smith,
D. L. Tucker,
S. Kent,
M. W. Richmond,
M. Fukugita,
T Ichikawa,
S. -I. Ichikawa,
A. M. Jorgensen,
A. Uomoto,
J. E. Gunn, [......],
A. Tolea,
A. Henden,
J. Annis, J. R. Pier,
T. A. McKay,
J. Brinkmann,
B Chen,
J. Holtzman,
K. Shimasaku,
D. G. York
[show abstract]
[hide abstract]
ABSTRACT: We present the 158 standard stars that define the u'g'r'i'z' photometric system. These stars form the basis for the photometric calibration of the Sloan Digital Sky Survey (SDSS). The defining instrument system and filters, the observing process, the reduction techniques, and the software used to create the stellar network are all described. We briefly discuss the history of the star selection process, the derivation of a set of transformation equations for the UBVRcIc system, and plans for future work.
02/2002;
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H. C. Harris,
B. M. S. Hansen,
J. Liebert,
D. E. Vanden Berk,
S. F. Anderson,
G. R. Knapp,
X Fan,
B. Margon,
J. A. Munn,
R. C. Nichol, [......],
S. Kent,
D. Q. Lamb,
R. H. Lupton,
H. J. Newberg,
D. J. Schlegel,
S. Smee,
M. A. Strauss,
A. R. Thakar,
A. Uomoto,
B. Yanny
[show abstract]
[hide abstract]
ABSTRACT: Early data taken during commissioning of the SDSS have resulted in the discovery of a very cool white dwarf. It appears to have stronger collision induced absorption from molecular hydrogen than any other known white dwarf, suggesting it has a cooler temperature than any other. While its distance is presently unknown, it has a surprisingly small proper motion, making it unlikely to be a halo star. An analysis of white dwarf cooling times suggests that this object may be a low-mass star with a helium core. The SDSS imaging and spectroscopy also recovered LHS 3250, the coolest previously known white dwarf, indicating that the SDSS will be an effective tool for identifying these extreme objects. Comment: 15 pages, including 5 figures. Accepted for Astrophysical Journal Letters
01/2001;
-
M. Odenkirchen,
E. K. Grebel,
C. M. Rockosi,
W. Dehnen,
R. Ibata,
H. -W. Rix,
A. Stolte,
C Wolf,
J. E. Anderson,
N. A. Bahcall,
J. Brinkmann,
I. Csabai,
G. Hennessy,
R. B. Hindsley,
Z. Ivezic,
R. H. Lupton,
J. A. Munn, J. R. Pier,
C. Stoughton,
D. G. York
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of two well-defined tidal tails emerging from the sparse remote globular cluster Palomar 5. These tails stretch out symmetrically to both sides of the cluster in the direction of constant Galactic latitude and subtend an angle of 2.6 degrees on the sky. The tails have been detected in commissioning data of the Sloan Digital Sky Survey (SDSS), providing deep five-color photometry in a 2.5 degrees wide band along the equator. The stars in the tails make up a substantial part (~1/3) of the current total population of cluster stars in the magnitude interval 19.5 < i* < 22.0. This reveals that the cluster is subject to heavy mass loss. The orientation of the tails provides an important key for the determination of the cluster's Galactic orbit. Comment: 7 pages, 3 postscript figures, accepted for publication in ApJ Letters
12/2000;
-
B. Yanny,
H. J. Newberg,
S. Kent,
S. A. Laurent-Muehleisen, J. R. Pier,
G. T. Richards,
C. Stoughton,
J. E. Anderson Jr,
J. Annis,
J. Brinkmann, [......],
G. S. Hennessy,
Z. Ivezic,
G. R. Knapp,
R. Lupton,
J. A. Munn,
T. Nash,
C. M. Rockosi,
D. P. Schneider,
J A Smith,
D. G. York
[show abstract]
[hide abstract]
ABSTRACT: A sample of 4208 objects with magnitude 15 < g* < 22 and colors of main sequence A stars has been selected from 370 square degrees of Sloan Digital Sky Survey (SDSS) commissioning observations. The data is from two long, narrow stripes, each with an opening angle of greater than 60 deg, at Galactic latitudes 36 < abs(b) < 63 on the celestial equator. An examination of the sample's distribution shows that these stars trace considerable substructure in the halo. Large overdensities of A-colored stars in the North at (l,b,R) = (350, 50, 46 kpc) and in the South at (157, -58, 33 kpc) and extending over tens of degrees are present in the halo of the Milky Way. Using photometry to separate the stars by surface gravity, both structures are shown to contain a sequence of low surface gravity stars consistent with identification as a blue horizontal branch (BHB). Both structures also contain a population of high surface gravity stars two magnitudes fainter than the BHB stars, consistent with their identification as blue stragglers (BSs). From the numbers of detected BHB stars, lower limits to the implied mass of the structures are 6x10^6 M_sun and 2x10^6 M_sun. The fact that two such large clumps have been detected in a survey of only 1% of the sky indicates that such structures are not uncommon in the halo. Simple spheroidal parameters are fit to a complete sample of the remaining unclumped BHB stars and yield (at r < 40 kpc) a fit to a halo distribution with flattening (c/a = 0.65+/-0.2) and a density falloff exponent of alpha = -3.2+/-0.3. Comment: AASTeX v5_0, 26 pages, 1 table, 20 figures, ApJ accepted
04/2000;
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[show abstract]
[hide abstract]
ABSTRACT: Optical Charge Coupled Device (CCD) astrometry was done at the U.S.
Naval Observatory Flagstaff Station (NOFS) to obtain positions of solar
system bodies to be encountered by the Galileo spacecraft. The objects
observed were the minor planets 951 Gaspra and 243 Ida, discussed in
this paper, and the Galilean satellites of Jupiter, to be discussed in
Paper II. Observations of Gaspra were made from April through August
1991, and Ida was observed from 1991 November through 1993 May. Each
observing campaign was followed by a successful encounter. The
instrumentation, techniques, analysis methods, and astrometric results
are described.
The Astronomical Journal 05/1994; 107:2290-2294. · 4.03 Impact Factor
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R. S. Harrington,
C. C. Dahn,
V. V. Kallarakal,
H. H. Guetter,
B. Y. Riepe,
R. L. Walker, J. R. Pier,
F. J. Vrba,
C. B. Luginbuhl,
H. C. Harris,
H. D. Ables
[show abstract]
[hide abstract]
ABSTRACT: Trigonometric parallaxes, relative proper motions, and photometry are
presented for 122 stars in 111 systems. Of these stars, 70 are brighter
than V = 10.0.
The Astronomical Journal 03/1993; 105:1571-1580. · 4.03 Impact Factor
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08/1992; 24:1139.
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08/1989; 21:1195.
-
C. C. Dahn,
R. S. Harrington,
V. V. Kallarakal,
H. H. Guetter,
C. B. Luginbuhl,
B. Y. Riepe,
R. L. Walker, J. R. Pier,
F. J. Vrba,
D. G. Monet,
H. D. Ables
[show abstract]
[hide abstract]
ABSTRACT: The paper presents trigonometric parallaxes, relative proper motions,
and photoelectric photometry for 98 stars in 95 astrometric plate
series. These values were determined using plate material obtained with
the 1.55-m astrometric reflector. The results of perturbation analyses
for W922 are presented.
The Astronomical Journal 12/1987; 95:237-246. · 4.03 Impact Factor
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D. P. Schneider,
G. T. Richards,
P. B. Hall,
M. A. Strauss,
S. F. Anderson,
T. A. Boroson,
N. P. Ross,
Y. Shen,
W. N. Brandt,
X. H. Fan, [......],
K. Pan, J. R. Pier,
T. N. Price,
D. H. Saxe,
D. J. Schlegel,
A. Simmons,
S. A. Snedden,
M. U. SubbaRao,
A. S. Szalay,
D. H. Weinberg
The Astronomical Journal, v.139, 2360-2373 (2010).
