Outer structure of the Galactic warp and flare: explaining the Canis Major over-density

By Y. Momany, S. Zaggia, G. Gilmore, G. Piotto, G. Carraro, L. Bedin, F. Angeli, INAF-OA Padova, I. Trieste, U. Cambridge and 2 more. 2006

253 citations recorded by the source corpus.

Aims. In this paper we derive the structure of the Galactic stellar warp and flare. Methods. We use 2MASS red clump and red giant stars, selected at mean and fixed heliocentric distances of $R_{\odot}\simeq3$, 7 and 17 kpc. Results. Our results can be summarized as follows: (i) a clear stellar warp signature is derived for the 3 selected rings, proving that the warp starts already within the solar circle; (ii) the derived stellar warp is consistent (both in amplitude and phase-angle) with that for the Galactic interstellar dust and neutral atomic hydrogen; (iii) the consistency and regularity of the stellar-gaseous warp is traced out to about $R_{\rm GC}\sim20$ kpc; (iv) the Sun seems not to fall on the line of nodes. The stellar warp phase-angle orientation ($\phi\sim15^{\circ}$) is close to the orientation angle of the Galactic bar and this, most importantly, produces an asymmetric warp for the inner $R_{\odot}\simeq3$ and 7 kpc rings; (v) a Northern/Southern warp symmetry is observed only for the ring at $R_{\odot}\simeq17$ kpc, at which the dependency on ϕ is weakened; (vi) treating a mixture of thin and thick disk stellar populations, we trace the variation with R GC of the disk thickness (flaring) and derive an almost constant scale-height (~0.65 kpc) within $R_{\rm GC}\sim15$ kpc. Further out, the disk flaring increase gradually reaching a mean scale-height of ~1.5 kpc at $R_{\rm GC}\sim23$ kpc; (vii) the derived outer disk warping and flaring provide further robust evidence that there is no disk radial truncation at $R_{\rm GC}\sim14$ kpc. Conclusions. In the particular case of the Canis Major (CMa) over-density we confirm its coincidence with the Southern stellar maximum warp occurring near $l\sim240^{\circ}$ (for $R_{\odot}\simeq7$ kpc) which brings down the Milky Way mid-plane by ~$3^{\circ}$ in this direction. The regularity and consistency of the stellar, gaseous and dust warp argues strongly against a recent merger scenario for Canis Major. We present evidence to conclude that all observed parameters (e.g. number density, radial velocities, proper motion etc) of CMa are consistent with it being a normal Milky Way outer-disk population, thereby leaving no justification for more complex interpretations of its origin. The present analysis or outer disk structure does not provide a conclusive test of the structure or origin of the Monoceros Ring. Nevertheless, we show that a warped flared Milky Way contributes significantly at the locations of the Monoceros Ring. Comparison of outer Milky Way $\ion{H}{i}$ and CO properties with those of other galaxies favors the suggestion that complex structures close to planar in outer disks are common, and are a natural aspect of warped and flaring disks.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/7f76063bff93b553c1e4a545e9a6778b73cde057

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Citations in the corpus

A FIRST CONSTRAINT ON THE THICK DISK SCALE LENGTH: DIFFERENTIAL RADIAL ABUNDANCES IN K GIANTS AT GALACTOCENTRIC RADII 4, 8, AND 12 kpc (2011, background): “Given the warp of the Galactic disk from Momany et al. (2006), and the scale-heights, scalelengths, and normalisations of the thin and thick disks in the solar neighbourhood from Jurić et al. (2008), the dotted lines in Fig.”
LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) — The survey's science plan (2012, background): “…have stirred considerable debate, with some investigatorsclaiming that these structures are evidence of warping and/or flaring of the stellar disk (Momany et al. 2006, Natarajan & Sikivie 2007), while others maintain that they are most likely remnants of merger events(Conn et al. 2007, Butler et…”
The Accretion Origin of the Milky Way’s Stellar Halo (2007, background): “1 kpc scale height of the thick disk cannot be a thick disk; this is the wellknown Low-Latitude stream (e.g., Newberg et al. 2002; Peñarrubia et al. 2005; Momany et al. 2006).”
Dwarf galaxy planes: the discovery of symmetric structures in the Local Group (2013, methodology): “The nearby (7 kpc) Canis Major over-density is situated at even lower Galactic latitude (b = −8◦), but it might be a substructure in the Galactic disc of the MW and not a MW satellite galaxy (Momany et al. 2006).”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, background): “The nature of this stream is unknown (cf. Xu et al. 2015): Unlike the Canis Major overdensity, which may be related to the warp, the ring appears to have its own identity after correcting for the warp (Momany et al. 2006) and may even rotate slightly faster than the disk (Ivezić et al. 2008).”
Dark matter in the Milky Way II. The HI gas distribution as a tracer of the gravitational potential (2007, background): “Others explain the over-densitieas due to the Galactic warp: Momany et al. (2004, 2006) and López-Corredoira (2006).”
The Cold Dark Matter Halos of Local Group Dwarf Spheroidals (2007, background): “A lively debate can be found in the literature, with arguments in favour of this system being a new galaxy (Mart́ınez-Delgado et al. 2005, Bellazzini et al. 2006) and against it (e.g. Momany et al. 2006, Moitinho et al. 2006).”
Mapping the Milky Way with LAMOST– III. Complicated spatial structure in the outer disc (2018, background): “Some others argued that it may be part of the flare or warp in the outer disc (Momany et al. 2006; Hammersley & López-Corredoira 2011).”
THE THICK DISKS OF SPIRAL GALAXIES AS RELICS FROM GAS-RICH, TURBULENT, CLUMPY DISKS AT HIGH REDSHIFT (2009, background): “The stellar disks of spiral galaxies do have some outer flaring, but it begins only at large radii and it affects mainly the thin disk (e.g., Alard 2000; Momany et al. 2006, for the Galaxy).”
Stellar Proper Motions in the Galactic Bulge from Deep Hubble Space Telescope ACS WFC Photometry (2008, background): “This is 1 disk scale height beneath the middisk (slightly more with the Milky Way disk warp; e.g., Momany et al. 2006); thus, the disk contribution to the field on the far side of the bulge should be rather lower than the near side.”
The Wobbly Galaxy : kinematics north and south with RAVE red-clump giants (2013, background): “…debris (see e.g. Penarrubia et al. 2005), the excitation of the disc caused by accretion events (e.g. Kazantzidis et al. 2008) or the Galactic warp (Momany et al. 2006), while Humphreys et al. (2011) conclude that the Hercules cloud is most likely due to a dynamical interaction of the thick disc…”
A-type stars in the Canada–France Imaging Survey – II. Tracing the height of the disc at large distances with Blue Stragglers (2018, background): “However, Momany et al. (2006) measure the maximum (absolute) warp height to be 0.6 kpc at l 240◦ at a distance of 16 kpc from the Sun.”
MAPPING THE STELLAR STRUCTURE OF THE MILKY WAY THICK DISK AND HALO USING SEGUE PHOTOMETRY (2009, methodology): “…States 4 Department of Physics & Astronomy and JINA: Joint Institute for Nuclear Astrophysics, Michigan State University, E. Lansing, MI, 48824, USA infrared telescope, or more recent work using 2MASS data (e.g. Momany et al. 2006; Reylé et al. 2009) or the GLIMPSE survey (Benjamin et al. 2005).”
The Milky Way’s stellar disk (2013, background): “…simplistic) explanations have been advanced to explain it: either purely as deposited stellar debris from a satellite that had merged on a low-latitude, low-eccentricity prograde orbit (e.g., Peñarrubia et al. 2005), or simply as a combination of a disk warp and flare (e.g., Momany et al. 2006).”
RINGS AND RADIAL WAVES IN THE DISK OF THE MILKY WAY (2015, background): “Initially, the community was divided over the origin of the Monoceros Ring, which was thought to be associated with an accreting dwarf galaxy (Martin et al. 2004; Peñarrubia et al. 2005)or the normal Galactic warp/flare profiles (Momany et al. 2004, 2006).”