WALLABY SWG1 Gas‐rich dwarfs in the Local Group
Emma Ryan‐Weber Bouchard, Jerjen, Koribalski, Meurer, Oosterloo, Wakker, Wilcots, Zucker
WALLABY: Local Group Emma Ryan‐Weber (Swinburne) The Local Group A test bed for galaxy formation and evolution
Credit: Mario Mateo
WALLABY: Local Group Emma Ryan‐Weber (Swinburne) The missing satellite problem
Credit Diemand Credit Johnston & Bullock
WALLABY: Local Group Emma Ryan‐Weber (Swinburne) SDSS field of streams & 20 new dwarfs
Credit Vasily Belokurov
WALLABY: Local Group Emma Ryan‐Weber (Swinburne) Mass function of MW satellites
Simon & Geha (2007)
WALLABY: Local Group Emma Ryan‐Weber (Swinburne) Mass function of MW satellites Effect of Reionization?
Simon & Geha (2007)
WALLABY: Local Group Emma Ryan‐Weber (Swinburne) HI mass vs. distance to MW/M31
Tidal stripping may provide a more plausible explana on of this rela onship
Grcevich & Putman (2009)
WALLABY: Local Group Emma Ryan‐Weber (Swinburne) A minimum dark matter halo mass? Detect HI to greater radii
Strigari et al. (2009)
Belokurov et al. (2007)
WALLABY: Local Group Emma Ryan‐Weber (Swinburne) Phoenix dwarf Gas stripping as a trigger for star formation
Gas has survived galac c winds and supernova explosions and triggers further star forma on.
Young et al. (2007)
WALLABY: Local Group Emma Ryan‐Weber (Swinburne) Leo T in HIPASS
ERW et al. 2008
WALLABY: Local Group Emma Ryan‐Weber (Swinburne) Leo T
WALLABY will be first blind survey of HI in the Local Group to be conducted with an interferometer. NOT having zero‐spacing data provides a significant advantage.
GMRT observa ons of Leo T Sensi vity 5.2mJy/beam/channel Channel width 1.65 km/s 30” beam
ERW et al. 2008
WALLABY: Local Group Emma Ryan‐Weber (Swinburne) Predictions for WALLABY
Expect to detect 60 galaxies with 4 MHI>1.5x10 M⊙ at 300 Based on the HIPASS HIMF and a measured 3x overdensity of HI galaxies in the Local Group. WALLABY: Local Group Emma Ryan‐Weber (Swinburne) SWG1 plan •Three ways of finding HI in dwarf galaxies in the local group ‐ cross match HI data with known dwarfs ‐ cross match HI data with newly discovered stellar overdensi es (SkyMapper, Pan‐STARRS) ‐ search for HI detec on without considering op cal data • How do you find galaxies in Galac c fluff, especially those that contains no stars? ‐ Use reprocessed Galac c All Sky Survey (GASS, McClure‐Griffiths 2009) data to determine a detec on method for LG dwarfs. WALLABY: Local Group Emma Ryan‐Weber (Swinburne) GASS Velocity res 0.82 km/s ‐400 Credit S. Janowiecki WALLABY: Local Group Emma Ryan‐Weber (Swinburne) Science questions to be addressed • How do galaxies retain/gain gas and form stars ? (we will be able to compile physical evidence of gas stripping and galaxy ‘harassment’) • As we move further from the ‘zone of destruc on’ — beyond 250–350 kpc from the Milky Way/M 31 (see Tolstoy et al. 2009) — do we find more gas‐rich dwarfs with 7 Mhalo ∼ 10 M⊙ ? • Is there a common minimum halo mass for star forma on (see, e.g., Warren et al. 2007) ? • Is a galaxy’s star forma on history and HI mass‐to‐light ra o dominated by ini al condi ons (total mass, baryon frac on), or distance to the nearest spiral ? • Are there any gas‐rich galaxies without stars ? (the Local Volume would be the best place to find them as low mass galaxies have the lowest detected star forma on efficiencies) WALLABY: Local Group Emma Ryan‐Weber (Swinburne)