HI in Local Group Dwarf Galaxies Jana Grcevich Advisor: Mary Putman Jana Grcevich Advisor: Mary Putman

HI in Local Group Dwarfs Limits on HI content of the newly discovered dwarfs HI in Leo T HI in other low-mass local group dwarfs Galactocentric Distance vs. HI content Halo Density Estimation Gas Accretion Limits on HI content of the newly discovered dwarfs HI in Leo T HI in other low-mass local group dwarfs Galactocentric Distance vs. HI content Halo Density Estimation Gas Accretion

Data HIPASS LAB GALFA Declination Range -90 to to to +38 Spatial Resolution 15.5’35.7’3.4’ Velocity Resolution 26.4 km/s1.3 km/s0.2 km/s

Mass Limit Relations HIPASS (26.4 km/s) M=2.38 x D 2 kpc M 0 LAB (10 km/s) M=6.24 x D 2 kpc M 0

HI Mass Upper Limits Bootes I60< 86 Bootes II60< 86 Coma Berenices 44< 46 Hercules140< 466 Leo IV160< 609 Segue23< 13 Ursa Major I 100< 6240 Ursa Major II 30< 562 Willman I38< 901 Canis Venetici I 220< 3.0 x 10 4 Canis Venetici II 150< 1.4 x 10 4 Object Distance HI Mass (kpc) (solar masses) HIPASSLAB

Leo T in GALFA Lowest luminosity galaxy discovered which has current star formation (Irwin et al T - “transition” Optical Vel. = 38.1 km/s HI Vel. = 35 km/s Lowest luminosity galaxy discovered which has current star formation (Irwin et al T - “transition” Optical Vel. = 38.1 km/s HI Vel. = 35 km/s

Leo T (Ryan-Weber et al in prep)

Non-detections & Confident Detections Additional galaxies not detected: Cetus, Sextans, Leo I, And III, And V, And VI, Leo II, Leo IV, Ursa Minor, Draco, and Sagittarius. Confident Detections: Antlia, Phoenix, Pegasus, Aquarius, and LGS3. Additional galaxies not detected: Cetus, Sextans, Leo I, And III, And V, And VI, Leo II, Leo IV, Ursa Minor, Draco, and Sagittarius. Confident Detections: Antlia, Phoenix, Pegasus, Aquarius, and LGS3.

Fornax Contours at 3, 7, 11, and 15 sigma Moment Map to km/s Unclear if cloud is part of typical MW emission, an HVC of separate origin, or the Fornax Dwarf Optical Vel. = 53 km/s HI Cloud Vel. = ~40 km/s Moment Map to km/s Unclear if cloud is part of typical MW emission, an HVC of separate origin, or the Fornax Dwarf Optical Vel. = 53 km/s HI Cloud Vel. = ~40 km/s

Sculptor Contours at 3, 5, 7, and 9 sigma Two clouds discovered by Carignan et al with Parkes/ATCA Optical Vel. = 102 km/s HI Vel. = 105 km/s Two clouds discovered by Carignan et al with Parkes/ATCA Optical Vel. = 102 km/s HI Vel. = 105 km/s

Sculptor Contours at 3, 5, 7, and 9 sigma Sculptor Dwarf is in the same direction as the Magellanic Stream and Sculptor Group Sky is crowded at this velocity Cloud could be a filament extending toward the sculptor group or a chance superposition Sculptor Dwarf is in the same direction as the Magellanic Stream and Sculptor Group Sky is crowded at this velocity Cloud could be a filament extending toward the sculptor group or a chance superposition

Sculptor (Putman 2003) Sculptor Dwarf l = b = -83.2

Tucana Contours at 3, 5, 7, and 9 sigma HI cloud first detected by Oosterloo et al. (1996) who claimed it was associated with the Magellanic Stream Optical Vel. = 184 km/s HI Vel. = 130 km/s ~54 km/s Velocity Difference HI cloud first detected by Oosterloo et al. (1996) who claimed it was associated with the Magellanic Stream Optical Vel. = 184 km/s HI Vel. = 130 km/s ~54 km/s Velocity Difference

Tucana (Putman 2003) Tucana l = b = -47.4

HI vs GC Distance

All Non- Detections Non- Detections And Ambiguous Detections Majority Confident Detections At > 10 5 Solar Masses

Mass Loss Mechanism Simulations suggest that ram pressure is the primary mass loss mechanism, assisted by tidal and possibly internal effects (Mayer et al 06; Mori & Burkert 01; Quilis & Moore 2001)

Diffuse Halo Medium Assume dwarfs in the transition region are being actively stripped of gas Density of hot halo medium is given by (Gunn & Gott 1972):  IGM  v 2 >    gas /3 Assume dwarfs in the transition region are being actively stripped of gas Density of hot halo medium is given by (Gunn & Gott 1972):  IGM  v 2 >    gas /3

Diffuse Halo Medium  IGM ~    gas /(3 v 2 ) = 2.2 x cm -3 Typical values for a Leo T-like progenitor  km s -1  gas ~ N HI,core /R ~ 1 x cm -2 /600 pc = 5.4 x10 -2 cm -3 v ~ 60 km s -1 (1D velocity dispersion for Local Group dwarf galaxies from Van den Bergh 1999a)  IGM ~    gas /(3 v 2 ) = 2.2 x cm -3 Typical values for a Leo T-like progenitor  km s -1  gas ~ N HI,core /R ~ 1 x cm -2 /600 pc = 5.4 x10 -2 cm -3 v ~ 60 km s -1 (1D velocity dispersion for Local Group dwarf galaxies from Van den Bergh 1999a)

Diffuse Halo Medium  IGM ~ 2.2 x cm -3 Observations suggest a hot gaseous corona with a mean density of 2 x cm -3 within 150 kpc (Sembach et al. 2003) Explanations: Orbits take them further in than they are now seen The diffuse halo medium is or was “clumpy” Leo T doesn’t represent the progenitor Other mass lowering mechanisms - reionization?  IGM ~ 2.2 x cm -3 Observations suggest a hot gaseous corona with a mean density of 2 x cm -3 within 150 kpc (Sembach et al. 2003) Explanations: Orbits take them further in than they are now seen The diffuse halo medium is or was “clumpy” Leo T doesn’t represent the progenitor Other mass lowering mechanisms - reionization?

Diffuse Halo Medium  IGM ~    gas /(3 v 2 ) = 7.4 x cm -3 Typical values for a larger mass progenitor  km s -1  gas ~ N HI,core /R ~ 1 x cm -2 /2 kpc = 1.6 x10 -2 cm -3 v ~ 60 km s -1  IGM ~    gas /(3 v 2 ) = 7.4 x cm -3 Typical values for a larger mass progenitor  km s -1  gas ~ N HI,core /R ~ 1 x cm -2 /2 kpc = 1.6 x10 -2 cm -3 v ~ 60 km s -1

Gas Accretion Average HI mass of galaxies 300 kpc out or more: 4 x 10 6 M 0 Galaxies within 300 kpc would contribute about 8 x 10 7 M 0 to the MW Average HI mass of galaxies 300 kpc out or more: 4 x 10 6 M 0 Galaxies within 300 kpc would contribute about 8 x 10 7 M 0 to the MW

Conclusions All of the SDSS dwarfs except Leo T are devoid of gas to our detection limits, and these upper limits are lower than the HI mass of any known dwarf which has HI. Dwarf galaxies at smaller galactocentric distances have less HI on average than those at larger distances. The HI -distance trend supports data from simulations which suggest ram-pressure stripping/tidal effects are responsible for the low HI content of dSphs The diffuse halo density can be estimated, but yields densities higher than expected Accretion from the dwarfs provides insufficient fuel to support long term star formation in the MW at the observed rate All of the SDSS dwarfs except Leo T are devoid of gas to our detection limits, and these upper limits are lower than the HI mass of any known dwarf which has HI. Dwarf galaxies at smaller galactocentric distances have less HI on average than those at larger distances. The HI -distance trend supports data from simulations which suggest ram-pressure stripping/tidal effects are responsible for the low HI content of dSphs The diffuse halo density can be estimated, but yields densities higher than expected Accretion from the dwarfs provides insufficient fuel to support long term star formation in the MW at the observed rate

Future Work HVC simulation by Fabian Heitsch Rel. Velocity = 150 km s -1 Cloud: R = 25 pc T = 1 x 10 4 K n = 0.5 cm -3 Ambient Gas: T = 5 x 10 6 K n = 1 x cm -3 Analysis of the star formation histories of the dwarfs and how this correlates with HI content Galfa observations of HI in the vicinity of local group dwarfs Simulations of gas clouds being stripped and study of head tail clouds Analysis of the star formation histories of the dwarfs and how this correlates with HI content Galfa observations of HI in the vicinity of local group dwarfs Simulations of gas clouds being stripped and study of head tail clouds