On the Continuing Formation of the Andromeda Galaxy: Detection of H
                    <scp>i</scp>
                    Clouds in the M31 Halo

Thilker, David A.; Braun, Róbert; Walterbos, R. A. M.; Corbelli, E.; Lockman, Felix J.; Murphy, E. M.; Maddalena, R. J.

doi:10.1086/381703

Cited by 188 publications

(299 citation statements)

References 29 publications

(27 reference statements)

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“…5.3 for complex C. In external galaxies, clouds are also detected at large distances and/or very anomalous velocities: e.g. the "forbidden" clouds in NGC 2403 (Fraternali et al 2002), the so-called counter-rotating clouds (see Fraternali 2010) and the clouds surrounding M 31 at tens of kpc from the disk (Thilker et al 2004). Very massive and very anomalous clouds are not consistent with a Galactic fountain origin.…”

Section: Comparison With External Galaxiesmentioning

confidence: 96%

Modelling the H i halo of the Milky Way

Marasco

Fraternali

2010

A&A

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Aims. We studied the global distribution and kinematics of the extra-planar neutral gas in the Milky Way.Methods. We built 3D models for a series of Galactic H i layers, projected them for an inside view, and compared them with the Leiden-Argentina-Bonn 21-cm observations. Results. We show that the Milky Way disk is surrounded by an extended halo of neutral gas with a vertical scale-height of 1.6 +0.6 −0.4 kpc and an H i mass of 3.2 +1.0 −0.9 × 10 8 M , which is ∼5−10% of the total Galactic H i. This H i halo rotates more slowly than the disk with a vertical velocity gradient of −15 ± 4 km s −1 kpc −1 . We found evidence for a global infall motion in the halo, both vertical (20 +5 −7 km s −1 ) and radial (30 +7 −5 km s −1 ). Conclusions.The Milky Way H i extra-planar layer shows properties similar to the halos of external galaxies, which is compatible with it being predominantly produced by supernova explosions in the disk. It is most likely composed of distinct gas complexes with masses of ∼10 4−5 M , of which the intermediate velocity clouds are the local manifestations. The classical high-velocity clouds appear to be a separate population.

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Section: Comparison With External Galaxiesmentioning

confidence: 96%

Modelling the H i halo of the Milky Way

Marasco

Fraternali

2010

A&A

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“…Our single dish GBT observations were obtained during 2002 October, using the same setup described by Thilker et al (2004) for M 31 observations. The telescope was scanned over a 5 × 5 deg region centered on M 33 while HI spectra were measured at a velocity resolution of 1.25 km s −1 .…”

Section: The Gaseous Diskmentioning

confidence: 99%

Dynamical signatures of a ΛCDM-halo and the distribution of the baryons in M 33

Corbelli

Thilker

Zibetti

et al. 2014

A&A

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Aims. We determine the mass distribution of stars, gas, and dark matter in M 33 to test cosmological models of galaxy formation and evolution. Methods. We map the neutral atomic gas content of M 33 using high resolution Very Large Array and Green Bank Telescope observations of the 21 cm HI line emission. A tilted ring model is fitted to the HI datacube to determine the varying spatial orientation of the extended gaseous disk and the rotation curve. We derive the stellar mass surface density map of M 33's optical disk via pixel-SED fitting methods based on population synthesis models that allow for positional changes in star formation history. Stellar and gas maps are used in the dynamical analysis of the rotation curve to constrain the dark halo properties. Results. The disk of M 33 warps from 8 kpc outward without substantial change of its inclination with respect to the line of sight; the line of nodes rotates clockwise toward the direction of M 31. Rotational velocities rise steeply with radius in the inner disk, reaching 100 km s −1 in 4 kpc, then the rotation curve becomes more perturbed and flatter with velocities as high as 120-130 km s −1 out to 2.7 R 25 . The stellar surface density map highlights a star-forming disk with a varying mass-to-light ratio. At larger radii, a dynamically relevant fraction of the baryons are in gaseous form. A dark matter halo with a Navarro-Frenk-White density profile, as predicted by hierarchical clustering and structure formation in a ΛCDM cosmology, provides the best fits to the rotation curve. Dark matter is relevant at all radii in shaping the rotation curve and the most likely dark halo has a concentration C 9.5 and a total mass of 4.3(±1.0) × 10 11 M . This imples a baryonic fraction of order 0.02 and the evolutionary history of this galaxy should therefore account for loss of a large fraction of its original baryonic content.

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“…3.1: both sets (Thilker et al 2004;Braun et al 2009) fully include the whole HELGA field (see e.g. Fig.…”

Section: Ancillary Datamentioning

confidence: 99%

“…), millimeter (Nieten et al 2006) and radio (e.g. Thilker et al 2004;Braun et al 2009). Despite this, the observational coverage in the sub-millimeter domain was until now limited by the absence of data longward of 170 μm, except for the extremely low resolution (with a beam size larger than 40 ) data from the Diffuse Infrared Background Experiment (DIRBE) at 240 μm (Odenwald et al 1998).…”

Section: Introduction An Overall View Of the Interstellar Medium Of Tmentioning

confidence: 99%

TheHerschelExploitation of Local Galaxy Andromeda (HELGA)

Fritz

Gentile

Smith

et al. 2012

A&A

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Context. We have obtained Herschel images at five wavelengths from 100 to 500 μm of a ∼5.5 × 2.5 degree area centred on the local galaxy M 31 (Andromeda), our nearest neighbour spiral galaxy, as part of the Herschel guaranteed time project "HELGA". The main goals of HELGA are to study the characteristics of the extended dust emission, focusing on larger scales than studied in previous observations of Andromeda at an increased spatial resolution, and the obscured star formation. Aims. In this paper we present data reduction and Herschel maps, and provide a description of the far-infrared morphology, comparing it with features seen at other wavelengths. Methods. We used high-resolution maps of the atomic hydrogen, fully covering our fields, to identify dust emission features that can be associated to M 31 with confidence, distinguishing them from emission coming from the foreground Galactic cirrus. Results. Thanks to the very large extension of our maps we detect, for the first time at far-infrared wavelengths, three arc-like structures extending out to ∼21, ∼26 and ∼31 kpc respectively, in the south-western part of M 31. The presence of these features, hosting ∼2.2 × 10 6 M of dust, is safely confirmed by their detection in HI maps. Overall, we estimate a total dust mass of ∼5.8 × 10 7 M , about 78% of which is contained in the two main ring-like structures at 10 and 15 kpc, at an average temperature of 16.5 K. We find that the gas-to-dust ratio declines exponentially as a function of the galacto-centric distance, in agreement with the known metallicity gradient, with values ranging from 66 in the nucleus to ∼275 in the outermost region. Conclusions. Dust in M 31 extends significantly beyond its optical radius (∼21 kpc) and what was previously mapped in the farinfrared. An annular-like segment, located approximately at R 25 , is clearly detected on both sides of the galaxy, and two other similar annular structures are undoubtedly detected on the south-west side even further out.

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

Cited by 188 publications

References 29 publications

Modelling the H i halo of the Milky Way

Modelling the H i halo of the Milky Way

Dynamical signatures of a ΛCDM-halo and the distribution of the baryons in M 33

TheHerschelExploitation of Local Galaxy Andromeda (HELGA)

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