Physical processesDrive the Abundance and Clustering of Neutral Atomic Hydrogen in Galaxies

in hierarchical galaxy formation model

Hansik Kim (UMelb)C. Power(ICRAR), S.Wyithe(UMelb), GALFORMers(ICC)

01/12/2011 Workshop on East-Asian Collaboration for SKAhansikk@unimelb.edu.au

Outline• Recipe of making Galaxy into the DM

haloes.• Distribution of predicted galaxy samples

and its implication. (Kim et al. 2010)

• Feedbacks to Abundance and Clustering of Galaxies.

• Summary.

Semi-Analytic Galaxy Formation Model

Properties of galaxy

Baugh 2006

Semi-analytic model

• Rapid exploration of the parameter space of galaxy formation physics.

• Large, statically useful samples.

• Wide range of properties, multi-wavebands.

Cole et al. 2000

Distribution of Galaxies

• Cold gas galaxies located in small mass of dark matter haloes.

• Most of cold gas galaxies are central galaxies.

Kim et al. 2011

HI mass from the simulation• Cold Gas to HI mass.

Fixed H2/HI ratio (cf. Baugh et al. 2004)Variable H2/HI ratio (cf. Obreschkow et al.

2009)Self-consistent predictions (cf. Lagos et

al. 2010)

Thanks to Lagos

Vcut=30km/s

Zcut=10

4 times better resolution than Millennium Simulation.

HIMF from self-consistent prediction

Performance prediction for the next generation surveys.

The forecast constrains on the dark energy equation of stateKim et al. 2011

Cover 20000deg2 in 1 yr

Abundance and Clusteringof Neutral Atomic Hydrogen in

Galaxies

Kim et al. 2011 (Preparation)

• Feedback processes. Supernovae(SNe) feedback Active Galactic Nuclei(AGN)

feedback Photo-ionization(PI) feedback

SNe feedback• SNe feedback is effective in low mass

galaxies.• SNe feedback is modelled in GALFORM as

• Vhot=485km/s and ahot=3.2

Changed overall range of LF.Changed intermediate of HIMF.

Mass cut

Resolution

The Halo Occupation Distribution (HOD) is a parameter of the halo model of galaxy clustering. The halo model provides one view of the large scale structure of the universe as clumps of dark matter, while the HOD provides a view of how galactic matter is distributed within each of the dark matter clumps. The HOD is used to describe three related properties of the halo model: the probability distribution relating the mass of a dark matter halo to the number of galaxies that form within that halo; the distribution in space of galactic matter within a dark matter halo; the distribution of velocities of galactic matter relative to dark matter within a dark matter halo.

Zehavi et al. 2010

Clustering strength depends on the strength of SNe feedback

AGN feedback• To understand the bright end of LF.• Suppress the cooling flows in

massive haloes.

AGN feedback leads changing

bright end of LF & High mass end of HIMF

Small effect on the clustering of HI galaxy

PI feedback• Ionization of the IGM suppresses cooling

onto dark matter haloes.• Vcut (the host halo’s circular velocity, 30km/s)

• Zcut (redshift, 10) in GALFORM.

Changed faint end of LF & low mass end of HIMF

by PI feedback strength

PI feedback give a huge difference to HI poor galaxy clustering

Summary & Future worksFuture HI survey results can predicted by physically motivated semi-analytic model.Semi-analytic model makes useful Mocks for the next generation HI galaxy surveys. Abundance and Clustering of HI galaxies are changed by Feedbacks.HI galaxy survey is one of important tools to constrain the galaxy formation models.

Morphological type dependence.Environment dependence.Self-consistent PI feedback.ReferencesPower, Baugh & Lacey (2010, MNRAS, 406, 43), Kim et al. (2011, MNRAS, 414, 2367)Lagos et al. (2011, MNRAS, 416, 1566), Lagos et al. (2011, accepted to MNRAS)Kim et al. (preparation)

Thank you!!

Normal Galaxy

Active Galaxy

Mock Galaxy