The ghost of sagittarius and lumps in the halo of the Milky Way

Heidi Jo Newberg, Brian Yanny, Connie Rockosi, Eva K. Grebel, Hans Walter Rix, Jon Brinkmann, Istvan Csabai, Greg Hennessy, Robert B. Hindsley, Rodrigo Ibata, Zeljko Ivezić, Don Lamb, E. Thomas Nash, Michael Odenkirchen, Heather A. Rave, Donald P. Schneider, J. Allyn Smith, Andrea Stolte, Donald G. York

Research output: Contribution to journalArticle

501 Citations (Scopus)

Abstract

We identify new structures in the halo of the Milky Way from positions, colors, and magnitudes of five million stars detected in the Sloan Digital Sky Survey. Most of these stars are within 1°.26 of the celestial equator. We present color-magnitude diagrams (CMDs) for stars in two previously discovered, tidally disrupted structures. The CMDs and turnoff colors are consistent with those of the Sagittarius dwarf galaxy, as had been predicted. In one direction, we are even able to detect a clump of red stars, similar to that of the Sagittarius dwarf, from stars spread across 110 deg2 of sky. Focusing on stars with the colors of F turnoff objects, we identify at least five additional overdensities of stars. Four of these may be pieces of the same halo structure, which would cover a region of the sky at least 40° in diameter, at a distance of 11 kpc from the Sun (18 kpc from the center of the Galaxy). The turnoff is significantly bluer than that of thick-disk stars, yet the stars lie closer to the Galactic plane than a power-law spheroid predicts. We suggest two models to explain this new structure. One possibility is that this new structure could be a new dwarf satellite of the Milky Way, hidden in the Galactic plane and in the process of being tidally disrupted. The other possibility is that it could be part of a disklike distribution of stars which is metal-poor, with a scale height of approximately 2 kpc and a scale length of approximately 10 kpc. The fifth overdensity, which is 20 kpc away, is some distance from the Sagittarius dwarf streamer orbit and is not associated with any known Galactic structure. We have tentatively identified a sixth overdensity in the halo. If this sixth structure is instead part of a smooth distribution of halo stars (the spheroid), then the spheroid must be very flattened, with axial ratio q = 0.5. It is likely that there are many smaller streams of stars in the Galactic halo.

Original languageEnglish (US)
Pages (from-to)245-274
Number of pages30
JournalAstrophysical Journal
Volume569
Issue number1 I
DOIs
StatePublished - Apr 10 2002

Fingerprint

ghosts
halos
stars
diagram
spheroids
color-magnitude diagram
color
power law
sky
galactic structure
metal
scale height
galactic halos
clumps
dwarf galaxies
equators
sun
distribution
galaxies
orbits

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Newberg, H. J., Yanny, B., Rockosi, C., Grebel, E. K., Rix, H. W., Brinkmann, J., ... York, D. G. (2002). The ghost of sagittarius and lumps in the halo of the Milky Way. Astrophysical Journal, 569(1 I), 245-274. https://doi.org/10.1086/338983
Newberg, Heidi Jo ; Yanny, Brian ; Rockosi, Connie ; Grebel, Eva K. ; Rix, Hans Walter ; Brinkmann, Jon ; Csabai, Istvan ; Hennessy, Greg ; Hindsley, Robert B. ; Ibata, Rodrigo ; Ivezić, Zeljko ; Lamb, Don ; Nash, E. Thomas ; Odenkirchen, Michael ; Rave, Heather A. ; Schneider, Donald P. ; Smith, J. Allyn ; Stolte, Andrea ; York, Donald G. / The ghost of sagittarius and lumps in the halo of the Milky Way. In: Astrophysical Journal. 2002 ; Vol. 569, No. 1 I. pp. 245-274.
@article{a1ac8807cf9a4a5c829eb35fe484a352,
title = "The ghost of sagittarius and lumps in the halo of the Milky Way",
abstract = "We identify new structures in the halo of the Milky Way from positions, colors, and magnitudes of five million stars detected in the Sloan Digital Sky Survey. Most of these stars are within 1°.26 of the celestial equator. We present color-magnitude diagrams (CMDs) for stars in two previously discovered, tidally disrupted structures. The CMDs and turnoff colors are consistent with those of the Sagittarius dwarf galaxy, as had been predicted. In one direction, we are even able to detect a clump of red stars, similar to that of the Sagittarius dwarf, from stars spread across 110 deg2 of sky. Focusing on stars with the colors of F turnoff objects, we identify at least five additional overdensities of stars. Four of these may be pieces of the same halo structure, which would cover a region of the sky at least 40° in diameter, at a distance of 11 kpc from the Sun (18 kpc from the center of the Galaxy). The turnoff is significantly bluer than that of thick-disk stars, yet the stars lie closer to the Galactic plane than a power-law spheroid predicts. We suggest two models to explain this new structure. One possibility is that this new structure could be a new dwarf satellite of the Milky Way, hidden in the Galactic plane and in the process of being tidally disrupted. The other possibility is that it could be part of a disklike distribution of stars which is metal-poor, with a scale height of approximately 2 kpc and a scale length of approximately 10 kpc. The fifth overdensity, which is 20 kpc away, is some distance from the Sagittarius dwarf streamer orbit and is not associated with any known Galactic structure. We have tentatively identified a sixth overdensity in the halo. If this sixth structure is instead part of a smooth distribution of halo stars (the spheroid), then the spheroid must be very flattened, with axial ratio q = 0.5. It is likely that there are many smaller streams of stars in the Galactic halo.",
author = "Newberg, {Heidi Jo} and Brian Yanny and Connie Rockosi and Grebel, {Eva K.} and Rix, {Hans Walter} and Jon Brinkmann and Istvan Csabai and Greg Hennessy and Hindsley, {Robert B.} and Rodrigo Ibata and Zeljko Ivezić and Don Lamb and Nash, {E. Thomas} and Michael Odenkirchen and Rave, {Heather A.} and Schneider, {Donald P.} and Smith, {J. Allyn} and Andrea Stolte and York, {Donald G.}",
year = "2002",
month = "4",
day = "10",
doi = "10.1086/338983",
language = "English (US)",
volume = "569",
pages = "245--274",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1 I",

}

Newberg, HJ, Yanny, B, Rockosi, C, Grebel, EK, Rix, HW, Brinkmann, J, Csabai, I, Hennessy, G, Hindsley, RB, Ibata, R, Ivezić, Z, Lamb, D, Nash, ET, Odenkirchen, M, Rave, HA, Schneider, DP, Smith, JA, Stolte, A & York, DG 2002, 'The ghost of sagittarius and lumps in the halo of the Milky Way', Astrophysical Journal, vol. 569, no. 1 I, pp. 245-274. https://doi.org/10.1086/338983

The ghost of sagittarius and lumps in the halo of the Milky Way. / Newberg, Heidi Jo; Yanny, Brian; Rockosi, Connie; Grebel, Eva K.; Rix, Hans Walter; Brinkmann, Jon; Csabai, Istvan; Hennessy, Greg; Hindsley, Robert B.; Ibata, Rodrigo; Ivezić, Zeljko; Lamb, Don; Nash, E. Thomas; Odenkirchen, Michael; Rave, Heather A.; Schneider, Donald P.; Smith, J. Allyn; Stolte, Andrea; York, Donald G.

In: Astrophysical Journal, Vol. 569, No. 1 I, 10.04.2002, p. 245-274.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The ghost of sagittarius and lumps in the halo of the Milky Way

AU - Newberg, Heidi Jo

AU - Yanny, Brian

AU - Rockosi, Connie

AU - Grebel, Eva K.

AU - Rix, Hans Walter

AU - Brinkmann, Jon

AU - Csabai, Istvan

AU - Hennessy, Greg

AU - Hindsley, Robert B.

AU - Ibata, Rodrigo

AU - Ivezić, Zeljko

AU - Lamb, Don

AU - Nash, E. Thomas

AU - Odenkirchen, Michael

AU - Rave, Heather A.

AU - Schneider, Donald P.

AU - Smith, J. Allyn

AU - Stolte, Andrea

AU - York, Donald G.

PY - 2002/4/10

Y1 - 2002/4/10

N2 - We identify new structures in the halo of the Milky Way from positions, colors, and magnitudes of five million stars detected in the Sloan Digital Sky Survey. Most of these stars are within 1°.26 of the celestial equator. We present color-magnitude diagrams (CMDs) for stars in two previously discovered, tidally disrupted structures. The CMDs and turnoff colors are consistent with those of the Sagittarius dwarf galaxy, as had been predicted. In one direction, we are even able to detect a clump of red stars, similar to that of the Sagittarius dwarf, from stars spread across 110 deg2 of sky. Focusing on stars with the colors of F turnoff objects, we identify at least five additional overdensities of stars. Four of these may be pieces of the same halo structure, which would cover a region of the sky at least 40° in diameter, at a distance of 11 kpc from the Sun (18 kpc from the center of the Galaxy). The turnoff is significantly bluer than that of thick-disk stars, yet the stars lie closer to the Galactic plane than a power-law spheroid predicts. We suggest two models to explain this new structure. One possibility is that this new structure could be a new dwarf satellite of the Milky Way, hidden in the Galactic plane and in the process of being tidally disrupted. The other possibility is that it could be part of a disklike distribution of stars which is metal-poor, with a scale height of approximately 2 kpc and a scale length of approximately 10 kpc. The fifth overdensity, which is 20 kpc away, is some distance from the Sagittarius dwarf streamer orbit and is not associated with any known Galactic structure. We have tentatively identified a sixth overdensity in the halo. If this sixth structure is instead part of a smooth distribution of halo stars (the spheroid), then the spheroid must be very flattened, with axial ratio q = 0.5. It is likely that there are many smaller streams of stars in the Galactic halo.

AB - We identify new structures in the halo of the Milky Way from positions, colors, and magnitudes of five million stars detected in the Sloan Digital Sky Survey. Most of these stars are within 1°.26 of the celestial equator. We present color-magnitude diagrams (CMDs) for stars in two previously discovered, tidally disrupted structures. The CMDs and turnoff colors are consistent with those of the Sagittarius dwarf galaxy, as had been predicted. In one direction, we are even able to detect a clump of red stars, similar to that of the Sagittarius dwarf, from stars spread across 110 deg2 of sky. Focusing on stars with the colors of F turnoff objects, we identify at least five additional overdensities of stars. Four of these may be pieces of the same halo structure, which would cover a region of the sky at least 40° in diameter, at a distance of 11 kpc from the Sun (18 kpc from the center of the Galaxy). The turnoff is significantly bluer than that of thick-disk stars, yet the stars lie closer to the Galactic plane than a power-law spheroid predicts. We suggest two models to explain this new structure. One possibility is that this new structure could be a new dwarf satellite of the Milky Way, hidden in the Galactic plane and in the process of being tidally disrupted. The other possibility is that it could be part of a disklike distribution of stars which is metal-poor, with a scale height of approximately 2 kpc and a scale length of approximately 10 kpc. The fifth overdensity, which is 20 kpc away, is some distance from the Sagittarius dwarf streamer orbit and is not associated with any known Galactic structure. We have tentatively identified a sixth overdensity in the halo. If this sixth structure is instead part of a smooth distribution of halo stars (the spheroid), then the spheroid must be very flattened, with axial ratio q = 0.5. It is likely that there are many smaller streams of stars in the Galactic halo.

UR - http://www.scopus.com/inward/record.url?scp=0001445469&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0001445469&partnerID=8YFLogxK

U2 - 10.1086/338983

DO - 10.1086/338983

M3 - Article

AN - SCOPUS:0001445469

VL - 569

SP - 245

EP - 274

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1 I

ER -

Newberg HJ, Yanny B, Rockosi C, Grebel EK, Rix HW, Brinkmann J et al. The ghost of sagittarius and lumps in the halo of the Milky Way. Astrophysical Journal. 2002 Apr 10;569(1 I):245-274. https://doi.org/10.1086/338983