Sara L. Ellison: University of Victoria Derek Fertig (GMU), Jess Rosenberg (GMU), Jillian Scudder (Uvic/Sussex), Hossein Teimoorinia (Uvic), Paul Torrey (CfA/MIT), Dave Patton (Trent), Trevor Mendel (MPE), Luc Simard (NRC- Herzberg) The role of HI in galaxy mergers.

About 1% of nearby galaxies are experiencing mergers and they seem to lead to some of the most spectacular cosmic events. QSO host galaxies from Canalizo & Stockton (2001) What are the implications for the gas reservoir of triggered star formation and black hole accretion?

DR7 pairs sample: Projected separation <80 kpc  V <300 km/s Mass ratio Yields: ~14,000 galaxies in pairs. Construct control samples that are matched in mass, redshift and environment: typically 100s control galaxies per pair. Measure changes differentially (  ). Galaxy pairs in the SDSS

Does the SFR enhancement in mergers depend on gas reservoir? Scudder et al. (2012) Projected separation (kpc)

Does the SFR enhancement in mergers depend on gas reservoir? Observations of 17 pairs with Jansky VLA: 2.5 σ correlation between SFR enhancement and gas fraction Scudder et al. in preparation

Fertig et al. submitted 223 matches to ALFALFA detections. 3.5 arcmin beam -> pair is blended. Matching is done based on wide pairs. No sign of gas depletion. Does merger-triggered star formation deplete the gas reservoir?

Extending the sample into the post-merger phase SFRs peak in post- merger phase, gas consumption may be most significant in coalesced galaxies? Ellison et al. (2013)

~100 post-mergers with ALFALFA matches or new Arecibo data Gas fraction enhancement of a factor 2-3!! Ellison et al. submitted

Random pairings will yield a gas fraction enhancement, with larger offsets for more gas-rich couplings.

Correct post-merger data for expected offset from pairings No evidence for significant gas consumption in mergers. Ellison et al., submitted

HI mass prediction with artificial neural networks, trained with α.40 Teimoorinia & Ellison, in prep.

Public catalog will be available in Teimoorinia & Ellison, in prep. Small scatter (σ~0.2 dex) and no systematic trends. Predictions for ~153,000 galaxies in SDSS.

Summary The enhancement in SFR weakly correlates with the HI gas content, Scudder et al., in prep There is no significant (HI) gas consumption in galaxy pairs, Fertig et al., submitted There is also no significant HI consumption in the post-merger phase (indeed, post-mergers are HI rich), Ellison et al. submitted Publicly available catalog of predicted HI masses for 153,000 SDSS galaxies: Teimoorina & Ellison in prep