The Ghost of Sagittarius and Lumps in the Halo of the Milky Way

By Heidi Jo Newberg, Brian Yanny, C. Rockosi, E. Grebel, Hans-Walter Rix, J. Brinkmann, István Csabai, G. Hennessy, R. Hindsley, R. Ibata and 9 more. 2001

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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.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/f91b9918ab485bdfa98708b1a6b5986420a8818f

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Citations in the corpus

Theoretical isochrones in several photometric systems. II. The Sloan Digital Sky Survey ugriz system (2004, background): “…special stellar objects (e.g., Margon et al. 2002; Hawley et al. 2002; Helmi et al. 2003), the study of resolved star clusters and nearby Milky Way satellites (e.g., Odenkirchen et al. 2001a,b), and studies of Milky Way substructure (e.g., Chen et al. 2001; Newberg et al. 2002; Yanny et al. 2003).”
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The stellar halo of the Galaxy (2008, background): “For example, fields at Galactic latitudes |b| < 25 deg are now known to contain significant substructure towards the anticenter (Newberg et al. 2002; Ibata et al. 2003; Grillmair 2006a).”
PROBING THE OUTER GALACTIC HALO WITH RR LYRAE FROM THE CATALINA SURVEYS (2012, methodology): “In addition to the Sgr stream, evidence has come for a Virgo stellar stream (VSS; Vivas & Zinn 2006; Vivas et al. 2008) using RRLs and a Virgo overdensity (VOD, Newberg et al. 2002) from F-type main-sequence stars (Newberg et al 2007).”
A Comprehensive Model for the Monoceros Tidal Stream (2004, background): “In the last decade, large-scale surveys have proved the existence of tidal streams (Sgr: Ibata et al. 1994; Monoceros: Newberg et al. 2002) in our Galaxy, providing strong observational evidence that disruption of dwarf satellites contributes to the assembly of some components of our Galaxy.”
Data Release 1 of the Dark Energy Spectroscopic Instrument (2025, neutral): “The map also shows high-metallicity stars extending above the disk at x = 20 kpc caused by the Monoceros “stream” structure ( H. J. Newberg et al. 2002; M. Juri ć et al. 2008 ) .”
CONSTRAINING THE MILKY WAY POTENTIAL WITH A SIX-DIMENSIONAL PHASE-SPACE MAP OF THE GD-1 STELLAR STREAM (2009, background): “…the SDSS data, such as the tidal tail of the Palomar 5 globular cluster (Odenkirchen et al. 2001; Grillmair & Dionatos 2006a), the Monoceros ring (Newberg et al. 2002), two northern tidal arms of the disrupting Sagittarius galaxy (Belokurov et al. 2006), the so called “Orphan” stream (Grillmair…”
A Two Micron All Sky Survey View of the Sagittarius Dwarf Galaxy. II. Swope Telescope Spectroscopy of M Giant Stars in the Dynamically Cold Sagittarius Tidal Stream (2004, background): “Interestingly, this is the general direction of the ‘‘ring’’ feature (Ibata et al. 2003; Yanny et al. 2003; Rocha-Pinto et al. 2003) identified with the potential ‘‘new galaxy’’ or tidal feature S223+20-19.4 by Newberg et al. (2002).”
The GALAH survey and Gaia DR2: dissecting the stellar disc’s phase space by age, action, chemistry, and location (2018, background): “Here, warps, rings and ripples are observed (e.g. Newberg et al. 2002; RochaPinto et al. 2004; Newberg et al. 2007) and these have been interpreted in terms of corrugations and waves triggered by a passing satellite (e.g. Quillen et al. 2009; Purcell et al. 2011; Widrow et al. 2012; Gómez et al.…”
The Magellanic Stream, High-Velocity Clouds, and the Sculptor Group (2002, background): “Many searches have been made for streams of halo material; the remnants of Galactic satellites which are responsible for building up the Milky Way (e.g. Newberg et al. 2002; Morrison et al.2000; Majewski et al.2000; Lynden-Bell & Lynden-Bell 1995).”
Star Counts Redivivus. IV. Density Laws through Photometric Parallaxes (2002, background): “…have been directly observed in giant stars (S. R. Majewski et al. 2002, in preparation), mainsequence stars (Majewski, Munn, & Hawley 1994, 1996; Newberg et al. 2002; Dinescu et al. 2002), and blue horizontal branch/RR Lyrae halo stars (Yanny et al. 2000; Ivezic et al. 2000; Vivas et al. 2001).”
Dark matter in the Milky Way II. The HI gas distribution as a tracer of the gravitational potential (2007, background): “Several groups – Newberg et al. (2002); Ibata et al. (2003); Yanny et al. (2003); Martin et al. (2005); Martı́nez-Delgado et al. (2005); Bellazzini et al. (2006) –have subsequently claimed to have detected stellar streams in the Milky Way, right at the region of interest.”
The Origin of the Bifurcation in the Sagittarius Stream (2006, background): “Ibata et al. (2001a) and Newberg et al. (2002, 2003) made early detections of Sgr tidal debris in data from the Sloan Digital Sky Survey (SDSS; see Hogg et al. 2001; Stoughton et al. 2002; Smith et al. 2002; Pier et al. 2003; Ivezić et al. 2004; Gunn et al. 2006).”
VLT/UVES Abundances in Four Nearby Dwarf Spheroidal Galaxies. I. Nucleosynthesis and Abundance Ratios (2002, background): “These include the current assimilation of the Sgr dwarf (Ibata et al. 1997; Dohm-Palmer et al. 2000; Newberg et al. 2002) and possibly !”
Vertical density waves in the Milky Way disc induced by the Sagittarius dwarf galaxy (2012, background): “An example is the kinematically cold structure known as the Monoceros ring (Newberg et al. 2002; Jurić et al. 2008), which naturally emerges in these simulations, although its origin is still a matter of debate (see Conn et al. 2012; Li et al. 2012; Lopez-Corredoira et al. 2012).”
The Wobbly Galaxy : kinematics north and south with RAVE red-clump giants (2013, background): “While within the disc itself there is evidence of large-scale stellar overdensities: outwards from the Sun at a Galactocentric distance of R = 18–20 kpc there is the Monoceros Stream (Newberg et al. 2002; Yanny et al. 2003), inwards from the Sun (d ∼ 2 kpc) there is the Hercules thick-disc cloud (HT”
LIGHT CURVE TEMPLATES AND GALACTIC DISTRIBUTION OF RR LYRAE STARS FROM SLOAN DIGITAL SKY SURVEY STRIPE 82 (2009, background): “The estimated fractional error in the heliocentric distance (d/σd) of 0.06 is smaller, by a factor of ∼ 2 − 4, than the fractional distance error for K giants (Dohm-Palmer et al. 2001), M giants (Majewski et al. 2003) or main sequence stars (Newberg et al. 2002; Jurić et al. 2008).”
The Lives of Stars: Insights from the TGAS–RAVE–LAMOST Data Set (2018, background): “…surveys, it was difficult to draw sweeping conclusions about these broad features, but the more one looked, the more evidence pointed to a fairly chaotic formation (see for example the lumpy Milky Way topography in Newberg et al. 2002, or the complex Magellanic system in Belokurov & Koposov 2016).”