Multiphase galaxy formation: high-velocity clouds and the missing baryon problem

By A. Maller, James S. Bullock. 2004

380 citations recorded by the source corpus.

The standard treatment of cooling in Cold Dark Matter halos assumes that all of the gas within a “cooling radius” cools and contracts monolithically to fuel galaxy formation. Here we take into account the expectation that the hot gas in galactic halos is thermally unstable and prone to fragmentation during cooling and show that the implications are more far-reaching than previously expected: allowing multi-phase cooling fundamentally alters expectations about gas infall in galactic halos and naturally gives rise to a characteristic upper-limit on the masses of galaxies, as observed. Specifically, we argue that cooling should proceed via the formation of high-density, � 10 4 K clouds, pressure-confined within a hot gas background. The background medium that emerges has a low density, and can survive as a hydrostatically stable corona with a long cooling time. The fraction of halo baryons contained in the residual hot core component grows with halo mass because the cooling density increases with gas temperature, and this leads to an upper-mass limit in quiescent, non-merged galaxies of � 10 11 M⊙. In this scenario, galaxy formation is fueled by the infall of pressure-supported clouds. For Milky-Way-size systems, clouds of mass � 5 × 10 6 M⊙ that formed or merged within the last several Gyrs should still exist as a residual population in the halo, with a total mass in clouds of � 2 × 10 10 M⊙. The baryonic mass of the Milky Way galaxy is explained naturally in this model, and is a factor of two smaller than would result in the standard treatment without feedback. We expect clouds in galactic halos to be � 1kpc in size and to extend � 150kpc from galactic centers. The predicted properties of Milky Way clouds match well the observed radial velocity distribution, angular sizes, column densities, and velocity widths of High Velocity Clouds around our Galaxy. The clouds we predict are also of the type needed to explain high-ion absorption systems at z < 1, and the predicted covering factor around external galaxies is consistent with observations.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/c838c04465508a3de8f3458484b97b8bd422de3c

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Citations in the corpus

How do galaxies get their gas (2002, background): “Maller & Bullock (2004) argue that a proper, multiphase treatment of hot halo gas reduces predicted accretion rates by a substantial factor, even without conduction or extra feedback, because the cooling gas forms dense clouds and the remaining gas has lower densities and longer cooling times.”
Time-dependent Ionization in Radiatively Cooling Gas (2006, background): “…spectroscopy of hot gas in the Galactic halo (e.g., Sembach&Savage 1992; Spitzer 1996), including,more recently, in discrete ionized ‘‘high-velocity clouds’’ (Savage et al. 2002; Fox et al. 2004, 2005, 2006; see also Sternberg et al. 2002; Gnat & Sternberg 2004; Maller & Bullock 2004).”
GASS: THE PARKES GALACTIC ALL-SKY SURVEY. I. SURVEY DESCRIPTION, GOALS, AND INITIAL DATA RELEASE (2009, background): “…Putman et al. 2003) or other satellites (e.g., Lockman 2003); some may be infalling intergalactic gas (e.g., Complex C; Wakker et al. 1999; Tripp et al. 2003; Lockman et al. 2008)l; and some may be associated with gas condensing from a massive, hot halo (Maller & Bullock 2004; Sommer-Larsen 2006).”
AN EMPIRICAL CHARACTERIZATION OF EXTENDED COOL GAS AROUND GALAXIES USING Mg ii ABSORPTION FEATURES (2010, methodology): “For example, the confining hot medium around the cool clouds is expected to have a low density and long cooling time, reducing the “overcooling problem” in standard galaxy formation models (e.g. Maller & Bullock 2004; Kaufmann et al. 2009).”
THE DUAL ORIGIN OF STELLAR HALOS (2009, background): “Maller & Bullock (2004) have shown that accounting for hot halo gas instabilities may be important in understanding the total baryonic mass of a galaxy.”
THE CIRCUMGALACTIC MEDIUM OF MASSIVE GALAXIES AT z ∼ 3: A TEST FOR STELLAR FEEDBACK, GALACTIC OUTFLOWS, AND COLD STREAMS (2012, background): “A clumpy, two-phase medium could be produced by thermal instabilities in the warm/hot halo around the main host (Maller & Bullock 2004; Kaufmann et al. 2006, 2009), although whether or not the conditions for thermal instabilities to operate are met in real galaxies is still a controversial issue…”
Multiphase High-Velocity Clouds toward HE 0226–4110 and PG 0953+414 (2005, background): “Within this paradigm, many HVCs (e.g., Complex C; Wakker et al. 1999) could represent material leftover from the galaxy forma- tion process (Oort 1970; Maller & Bullock 2004) or else material stripped from nearby galaxies (e.g., the Magellanic Stream; Gardiner & Noguchi 1996).”
Massive Primordial Black Holes as Dark Matter and their detection with Gravitational Waves (2017, methodology): “persion velocity of the gas in the accretion disk around it. From Ref. [47]. BBN light element abundance. There seems to be less in the present universe in hot plasmas around clusters and in galaxies [57]. They may simply not shine or they could be locked inside the PBH that account for the CDM in t”
Gaseous Galaxy Halos (2012, background): “…to cosmological models of galaxy formation, as they predict it extends out to the virial radius and potentially hosts a large percentage of the galaxy’s baryons (White & Rees, 1978; Maller & Bullock, 2004; Fukugita & Peebles, 2006; Kaufmann et al., 2006; Sommer-Larsen, 2006; Crain et al., 2010).”
THE BIMODAL METALLICITY DISTRIBUTION OF THE COOL CIRCUMGALACTIC MEDIUM AT z ≲ 1 (2013, background): “Stars cannot continue to form in galaxies over billions of years without a replenishment of gas from the IGM (e.g., Maller & Bullock 2004; Dekel & Birnboim 2006), while feedback from star formation and AGN activity can fuel massive outflows from a gas-rich galaxy that may choke off star formation…”
A High-Resolution Survey of Low-Redshift QSO Absorption Lines: Statistics and Physical Conditions of O VI Absorbers (2007, background): “Multiphase absorption could be more likely to occur in gas accreting into deeper potential wells because such locations are likely sites for shock heating but could also be places where more gas cools quickly due to processes such as thermal instability (e.g., Maller & Bullock 2004).”
Lyα Radiation from Collapsing Protogalaxies. I. Characteristics of the Emergent Spectrum (2005, background): “The density distribution of the baryons, b(r), is assumed to trace the dark matter at large radii, with a thermal core at r 3Rs/4 (see Maller & Bullock 2004, their eqs.”
Tracing Galaxy Formation with Stellar Halos. I. Methods (2005, background): “(12) In the absence of radiative feedback effects, cooling is extremely efficient in pre-merged satellites of the size we consider (see, e.g. Maller & Bullock 2004).”
THIRD-EPOCH MAGELLANIC CLOUD PROPER MOTIONS. I. HUBBLE SPACE TELESCOPE/WFC3 DATA AND ORBIT IMPLICATIONS (2013, methodology): “We model the concentration evolution following Klypin et al. (2011), and the scaling of the virial radius with redshift and mass following relations in Maller & Bullock (2004)7.”
A Global Model for Circumgalactic and Cluster-core Precipitation (2016, background): “Many subsequent papers have made interesting use of the cooling-time to freefall time ratio to analyze how galaxies form and evolve (e.g., Blumenthal et al. 1984; Fall & Rees 1985; Maller & Bullock 2004).”
X-ray coronae in simulations of disc galaxy formation (2010, background): “Such clouds may well have formed from thermal instability and fragmentation of hot coronal gas (e.g. Maller & Bullock 2004; Booth & Theuns 2007).”
THE COS-HALOS SURVEY: PHYSICAL CONDITIONS AND BARYONIC MASS IN THE LOW-REDSHIFT CIRCUMGALACTIC MEDIUM (2014, methodology): “In the following, we adopt the formalism of (Maller & Bullock 2004, hereafter MB04) who expanded upon the Mo & Miralda-Escude (1996) treatment.”
Λ Cold Dark Matter, Stellar Feedback, and the Galactic Halo Abundance Pattern (2005, background): “In the models we explore below we assume for simplicity that star formation is truncated soon after each satellite halo is accreted onto the Milky Way host as a result of ram-pressure stripping from the background hot gas halo (Moore & Davis 1994; Maller & Bullock 2004).”