On the Continuing Formation of the Andromeda Galaxy: Detection of H I Clouds in the M31 Halo

By D. Thilker, R. Braun, R. Walterbos, E. Corbelli, F. J. Lockman, E. Murphy, R. Maddalena. 2003

169 citations recorded by the source corpus.

Green Bank Telescope 21 cm observations have revealed a faint, yet extensive H I cloud population surrounding the Andromeda galaxy (M31). The newfound objects are likely analogs to the high-velocity H I clouds seen around the Milky Way. At least 20 discrete features are detected within 50 kpc of the M31 disk, with radial velocities that are comparable to those of outer disk rotation. In addition, a filamentary "halo" component of at least 30 kpc extent is concentrated at the M31 systemic velocity. Some of the discrete features are organized into elongated systems with velocity continuity, suggestive of tidal streams. The discrete population can be characterized by a steep power-law distribution of number versus H I mass in the range between 105 and 107 M☉. The velocity line width of discrete clouds is correlated with the cloud H I mass such that if the clouds are gravitationally bound this implies a dark matter to H I mass ratio of ~100 : 1. Possible origins for the discrete and halo M31 features include a Local Group "cooling flow," tidal debris from recent mergers or interactions, and the gaseous counterparts of low-mass dark matter halos.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/ff7c30565942d78759fc69a1fe899749b26e5dff

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Citations in the corpus

Simultaneous ram pressure and tidal stripping; how dwarf spheroidals lost their gas (2005, background): “These blobs could explain the cold H I fragments identified by Thilker et al. (2004) around M31.”
On the Accretion Origin of a Vast Extended Stellar Disk around the Andromeda Galaxy (2005, methodology): “H I content Recently, Thilker et al. (2004a) have presented an analysis of Green Bank Telescope λ21 cm observations of M31 and its environment.”
X-ray coronae in simulations of disc galaxy formation (2010, background): “…high-velocity clouds (HVCs) are abundant in the Milky Way and nearby disc galaxies and may be transporting a significant mass of cold gas to their discs (e.g. Oort 1970; Kerp et al. 1996; Wakker & van Woerden 1997; Wakker et al. 1999; Tripp et al. 2003; Thilker et al. 2004; Miller et al. 2009).”
The Cold Gaseous Halo of NGC 891 (2007, background): “Recently, a search has been carried out toward the two largest members of the Local Group other than the Milky Way, M31 and M33 (Westmeier et al. 2005), and a population of high-velocity clouds at large distances from these galaxies (about 50 kpc from M31; Thilker et al. 2004) has been found.”
Thermal instability and the feedback regulation of hot haloes in clusters, groups and galaxies (2011, background): “…in hot halos has also been invoked (e.g., Maller & Bullock 2004; Sommer-Larsen 2006; Peek, Putman, & Sommer-Larsen 2008) as a source of the high velocity clouds (HVCs) of neutral hydrogen observed in the Galactic halo (e.g., Wakker & van Woerden 1997) and in the halo of M31 (Thilker et al. 2004).”
A WIDE-FIELD HIGH-RESOLUTION H i MOSAIC OF MESSIER 31. I. OPAQUE ATOMIC GAS AND STAR FORMATION RATE DENSITY (2009, background): “◦8 and due South of M31 (Thilker et al. 2004) is also somewhat attenuated.”
Cold gas accretion in galaxies (2008, methodology): “H I observations with the Green Bank Telescope (GBT) by Thilker et al. (2004) [127] have revealed a population of faint H I clouds (at least 20) surrounding M 31 within 50 kpc of its disk (Fig.”
Gaseous Galaxy Halos (2012, methodology): “The spiral galaxy that has been mapped to the deepest levels (NHI < 10 18 cm−2) at a resolution of a few kpc, and is most similar to the Milky Way, is M31 (Thilker et al., 2004; Westmeier et al., 2005a).”
The Detailed Star Formation History in the Spheroid, Outer Disk, and Tidal Stream of the Andromeda Galaxy (2006, background): “The fact that such material continues to fall into Andromeda is evidenced by the extensive population of HI clouds recently found in the outskirts of the galaxy (Thilker et al. 2004).”
The Arecibo Legacy Fast ALFA Survey. I. Science Goals, Survey Design, and Strategy (2005, background): “While Arecibo cannot reach as far north as M31, ALFALFAwill cover part of the region containing the clouds in its periphery identified by Thilker et al. (2004) and their possible extension toward the region around M33 (Westmeier et al. 2005).”
HI4PI: a full-sky H i survey based on EBHIS and GASS (2016, background): “1 displays a part of the Leading Arm region (row 2; Brüns et al. 2005; Venzmer et al. 2012; For et al. 2013) of the Magellanic Clouds (row 3; Kim et al. 2003; Brüns et al. 2005) and the M31/M33 region (row 4; Braun et al. 2003; Thilker et al. 2004; Wolfe et al. 2016; Kerp et al. 2016a).”