Identification of a-colored stars and structure in the halo of the Milky Way from Sloan digital sky survey commissioning data

Brian Yanny, Heidi Jo Newberg, Steve Kent, Sally A. Laurent-Muehleisen, Jeffrey R. Pier, Gordon T. Richards, Chris Stoughton, John E. Anderson, James Annis, J. Brinkmann, Bing Chen, I. Csabai, Mamoru Doi, Masataka Fukugita, G. S. Hennessy, Željko Ivezić, G. R. Knapp, Robert Lupton, Jeffrey A. Munn, Thomas NashConstance M. Rockosi, Donald P. Schneider, J. Allyn Smith, Donald G. York

Research output: Contribution to journalArticle

259 Citations (Scopus)

Abstract

A sample of 4208 objects with magnitude 15 <g* <22 and colors of main-sequence A stars have been selected from 370 deg2 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°, at Galactic latitudes 36° <|b| <63° on the celestial equator. Relative photometric calibrations good to 2% and consistent absolute photometry allows this uniform sample to be treated statistically over the large area. 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. Ivezic et al. have detected the northern structure from a sample of RR Lyrae stars in the SDSS. 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 2 mag fainter than the BHB stars, consistent with their identification as blue stragglers (BSs). The majority of the high surface gravity stars in the Galactic halo may be BS stars like these. A population of F stars associated with the A star excess in the southern structure is detected (the F stars in the northern structure at 46 kpc would be too faint for the SDSS to detect). From the numbers of detected BHB stars, lower limits to the implied mass of the structures are 6 × 106 M and 2 × 106 M, although one does not yet know the full spatial extent of the structures. 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 a = -3.2 ± 0.3.

Original languageEnglish
Pages (from-to)825-841
Number of pages17
JournalAstrophysical Journal
Volume540
Issue number2 PART 1
Publication statusPublished - Sep 10 2000

Fingerprint

halos
blue stars
gravity
stars
horizontal branch stars
gravitation
F stars
A stars
photometry
calibration
galactic halos
main sequence stars
flattening
clumps
equators
substructures
sky
examination
exponents
color

Keywords

  • Blue stragglers
  • Galaxy: halo
  • Galaxy: structure
  • Stars: early-type
  • Stars: horizontal-branch

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Space and Planetary Science

Cite this

Yanny, B., Newberg, H. J., Kent, S., Laurent-Muehleisen, S. A., Pier, J. R., Richards, G. T., ... York, D. G. (2000). Identification of a-colored stars and structure in the halo of the Milky Way from Sloan digital sky survey commissioning data. Astrophysical Journal, 540(2 PART 1), 825-841.

Identification of a-colored stars and structure in the halo of the Milky Way from Sloan digital sky survey commissioning data. / Yanny, Brian; Newberg, Heidi Jo; Kent, Steve; Laurent-Muehleisen, Sally A.; Pier, Jeffrey R.; Richards, Gordon T.; Stoughton, Chris; Anderson, John E.; Annis, James; Brinkmann, J.; Chen, Bing; Csabai, I.; Doi, Mamoru; Fukugita, Masataka; Hennessy, G. S.; Ivezić, Željko; Knapp, G. R.; Lupton, Robert; Munn, Jeffrey A.; Nash, Thomas; Rockosi, Constance M.; Schneider, Donald P.; Smith, J. Allyn; York, Donald G.

In: Astrophysical Journal, Vol. 540, No. 2 PART 1, 10.09.2000, p. 825-841.

Research output: Contribution to journalArticle

Yanny, B, Newberg, HJ, Kent, S, Laurent-Muehleisen, SA, Pier, JR, Richards, GT, Stoughton, C, Anderson, JE, Annis, J, Brinkmann, J, Chen, B, Csabai, I, Doi, M, Fukugita, M, Hennessy, GS, Ivezić, Ž, Knapp, GR, Lupton, R, Munn, JA, Nash, T, Rockosi, CM, Schneider, DP, Smith, JA & York, DG 2000, 'Identification of a-colored stars and structure in the halo of the Milky Way from Sloan digital sky survey commissioning data', Astrophysical Journal, vol. 540, no. 2 PART 1, pp. 825-841.
Yanny B, Newberg HJ, Kent S, Laurent-Muehleisen SA, Pier JR, Richards GT et al. Identification of a-colored stars and structure in the halo of the Milky Way from Sloan digital sky survey commissioning data. Astrophysical Journal. 2000 Sep 10;540(2 PART 1):825-841.
Yanny, Brian ; Newberg, Heidi Jo ; Kent, Steve ; Laurent-Muehleisen, Sally A. ; Pier, Jeffrey R. ; Richards, Gordon T. ; Stoughton, Chris ; Anderson, John E. ; Annis, James ; Brinkmann, J. ; Chen, Bing ; Csabai, I. ; Doi, Mamoru ; Fukugita, Masataka ; Hennessy, G. S. ; Ivezić, Željko ; Knapp, G. R. ; Lupton, Robert ; Munn, Jeffrey A. ; Nash, Thomas ; Rockosi, Constance M. ; Schneider, Donald P. ; Smith, J. Allyn ; York, Donald G. / Identification of a-colored stars and structure in the halo of the Milky Way from Sloan digital sky survey commissioning data. In: Astrophysical Journal. 2000 ; Vol. 540, No. 2 PART 1. pp. 825-841.
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title = "Identification of a-colored stars and structure in the halo of the Milky Way from Sloan digital sky survey commissioning data",
abstract = "A sample of 4208 objects with magnitude 15 2 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°, at Galactic latitudes 36° <|b| <63° on the celestial equator. Relative photometric calibrations good to 2{\%} and consistent absolute photometry allows this uniform sample to be treated statistically over the large area. 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. Ivezic et al. have detected the northern structure from a sample of RR Lyrae stars in the SDSS. 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 2 mag fainter than the BHB stars, consistent with their identification as blue stragglers (BSs). The majority of the high surface gravity stars in the Galactic halo may be BS stars like these. A population of F stars associated with the A star excess in the southern structure is detected (the F stars in the northern structure at 46 kpc would be too faint for the SDSS to detect). From the numbers of detected BHB stars, lower limits to the implied mass of the structures are 6 × 106 M⊙ and 2 × 106 M⊙, although one does not yet know the full spatial extent of the structures. 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 a = -3.2 ± 0.3.",
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T1 - Identification of a-colored stars and structure in the halo of the Milky Way from Sloan digital sky survey commissioning data

AU - Yanny, Brian

AU - Newberg, Heidi Jo

AU - Kent, Steve

AU - Laurent-Muehleisen, Sally A.

AU - Pier, Jeffrey R.

AU - Richards, Gordon T.

AU - Stoughton, Chris

AU - Anderson, John E.

AU - Annis, James

AU - Brinkmann, J.

AU - Chen, Bing

AU - Csabai, I.

AU - Doi, Mamoru

AU - Fukugita, Masataka

AU - Hennessy, G. S.

AU - Ivezić, Željko

AU - Knapp, G. R.

AU - Lupton, Robert

AU - Munn, Jeffrey A.

AU - Nash, Thomas

AU - Rockosi, Constance M.

AU - Schneider, Donald P.

AU - Smith, J. Allyn

AU - York, Donald G.

PY - 2000/9/10

Y1 - 2000/9/10

N2 - A sample of 4208 objects with magnitude 15 2 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°, at Galactic latitudes 36° <|b| <63° on the celestial equator. Relative photometric calibrations good to 2% and consistent absolute photometry allows this uniform sample to be treated statistically over the large area. 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. Ivezic et al. have detected the northern structure from a sample of RR Lyrae stars in the SDSS. 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 2 mag fainter than the BHB stars, consistent with their identification as blue stragglers (BSs). The majority of the high surface gravity stars in the Galactic halo may be BS stars like these. A population of F stars associated with the A star excess in the southern structure is detected (the F stars in the northern structure at 46 kpc would be too faint for the SDSS to detect). From the numbers of detected BHB stars, lower limits to the implied mass of the structures are 6 × 106 M⊙ and 2 × 106 M⊙, although one does not yet know the full spatial extent of the structures. 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 a = -3.2 ± 0.3.

AB - A sample of 4208 objects with magnitude 15 2 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°, at Galactic latitudes 36° <|b| <63° on the celestial equator. Relative photometric calibrations good to 2% and consistent absolute photometry allows this uniform sample to be treated statistically over the large area. 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. Ivezic et al. have detected the northern structure from a sample of RR Lyrae stars in the SDSS. 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 2 mag fainter than the BHB stars, consistent with their identification as blue stragglers (BSs). The majority of the high surface gravity stars in the Galactic halo may be BS stars like these. A population of F stars associated with the A star excess in the southern structure is detected (the F stars in the northern structure at 46 kpc would be too faint for the SDSS to detect). From the numbers of detected BHB stars, lower limits to the implied mass of the structures are 6 × 106 M⊙ and 2 × 106 M⊙, although one does not yet know the full spatial extent of the structures. 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 a = -3.2 ± 0.3.

KW - Blue stragglers

KW - Galaxy: halo

KW - Galaxy: structure

KW - Stars: early-type

KW - Stars: horizontal-branch

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