The Westerbork Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) survey

Heald, G.; Józsa, G. I. G.; Serra, P.; Zschaechner, Laura K.; Rand, Richard J.; Fraternali, Filippo; Oosterloo, Tom; Walterbos, R. A. M.; Jütte, E.; Gentile, Gianfranco

doi:10.1051/0004-6361/201015938

Cited by 194 publications

(246 citation statements)

References 66 publications

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“…The observations are part of the Westerbork Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) survey (see Heald et al 2011) and go significantly deeper than previous H observations.…”

Section: Discussionmentioning

confidence: 82%

“…This material includes hot X-ray emitting gas (e.g. Tüllmann et al 2006;Li et al 2008), ionised gas (Collins & Rand 2001;Rossa & Dettmar 2003), dust (Howk & Savage 1999;Ménard et al 2010), and neutral hydrogen (Fraternali et al 2002;Oosterloo et al 2007;Heald et al 2011). The material is found to be often (but not always, in the case of the H) closely associated with star formation in the galaxy disk.…”

Section: Introductionmentioning

confidence: 99%

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HALOGAS: Extraplanar gas in NGC 3198

Gentile

Józsa

Serra

et al. 2013

A&A

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We present the analysis of new, deep H observations of the spiral galaxy NGC 3198 as part of the Westerbork Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) survey, with the main aim of investigating the presence, amount, morphology, and kinematics of extraplanar gas. We present models of the H observations of NGC 3198. The model that matches best the observed data cube features a thick disk with a scale height of ∼3 kpc and an H mass of about 15% of the total H mass; this thick disk also has a decrease in rotation velocity as a function of height (lag) of 7-15 km s −1 kpc −1 (though with large uncertainties). This extraplanar gas is detected for the first time in NGC 3198. Radially, this gas appears to extend slightly beyond the actively star-forming body of the galaxy (as traced by the Hα emission), but it is not more radially extended than the outer, fainter parts of the stellar disk. Compared to previous studies, thanks to the improved sensitivity we trace the rotation curve out to larger radii. We model the rotation curve in the framework of modified Newtonian dynamics (MOND) and confirm that, with the allowed distance range we assumed, fit quality is modest in this galaxy, but the new outer parts are explained in a satisfactory way.

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“…The observations are part of the Westerbork Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) survey (see Heald et al 2011) and go significantly deeper than previous H observations.…”

Section: Discussionmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

HALOGAS: Extraplanar gas in NGC 3198

Gentile

Józsa

Serra

et al. 2013

A&A

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“…To characterize faint diffuse gas in local galaxies, Heald et al (2011) have initiated the HALOGAS (Westerbork Hydrogen Accretion in LOcal GAlaxieS) survey. Their deep HI survey is designed to search for extraplanar gas in edge-on and inclined nearby galaxies and to determine the distribution and gas properties.…”

Section: Neutral Gas Observationsmentioning

confidence: 99%

Star formation sustained by gas accretion

Alméida

Elmegreen

Muñoz–Tuñón

et al. 2014

Astron Astrophys Rev

177

130

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Numerical simulations predict that metal-poor gas accretion from the cosmic web fuels the formation of disk galaxies. This paper discusses how cosmic gas accretion controls star formation, and summarizes the physical properties expected for the cosmic gas accreted by galaxies. The paper also collects observational evidence for gas accretion sustaining star formation. It reviews evidence inferred from neutral and ionized hydrogen, as well as from stars. A number of properties characterizing large samples of star-forming galaxies can be explained by metal-poor gas accretion, in particular, the relationship among stellar mass, metallicity, and star-formation rate (the so-called fundamental metallicity relationship). They are put forward and analyzed. Theory predicts gas accretion to be particularly important at high redshift, so indications based on distant objects are reviewed, including the global star-formation history of the universe, and the gas around galaxies as inferred from absorption features in the spectra of background sources.

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“…Most of this gas is located within ∼ 8 kpc from the disc with a filament extending up to about 20 kpc. Although we now regard NGC 891 as a remarkable and likely extreme case of the phenomenon of extraplanar gas, several other galaxies observed with the right sensitivity also show the presence of this component (e.g., Fraternali et al 2002;Barbieri et al 2005;Heald et al 2011). In particular galaxies with SFRs of order 1 M yr −1 seem to contain substantial amounts of extraplanar gas (e.g., Boomsma et al 2008;Marasco & Fraternali 2011;Gentile et al 2013).…”

Section: Inventory Of Gas Accretion In the Local Universementioning

confidence: 75%

How can star formation be sustained?

Fraternali

2013

Proc. IAU

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Abstract. There is overwhelming evidence that the Milky Way has formed its stars at a relatively constant rate throughout the Hubble time. This implies that its stock of cold gas was not in place since the beginning but it has been acquired slowly through gas accretion. The gas accretion must have been at low metallicity in order to reconcile the metallicities observed in the disc with the predictions of chemical evolution models. But how does this gas accretion take place? I review the current evidence of gas accretion into the Milky Way and similar galaxies through the infall of cold gas clouds and satellites. The conclusion from these studies is that the infalling gas at high column densities observed in HI emission is a least one order of magnitude below the value required to sustain star formation, thus accretion must come from a different channel. The likely reservoir for gas accretion is the cosmological corona of virial-temperature gas in which every galaxy must be embedded. At the interface between the disc and the corona the cold high-metallicity disc gas and the hot coronal medium must mix efficiently and this mixing causes the cooling and accretion of the lower corona. I show how this mechanism reproduces the kinematics of the neutral extraplanar gas in the Milky Way and other nearby galaxies and the ionised high-velocity clouds observed in HST spectra. I conclude with the speculation that the loss in efficiency of the disc-corona interaction is the ultimate cause for the evolution of disc galaxies towards the red sequence.

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The Westerbork Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) survey

Cited by 194 publications

References 66 publications

HALOGAS: Extraplanar gas in NGC 3198

HALOGAS: Extraplanar gas in NGC 3198

Star formation sustained by gas accretion

How can star formation be sustained?

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