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The Faintest Dwarf Galaxies in Groups and Poor Clusters

The Faintest Dwarf Galaxies in Groups and Poor Clusters. R. Marzke & A. Danielson (SFSU) M. Hudson (U. Waterloo) R. Windhorst (ASU). 1. Supernova feedback, photoionization. Galaxy luminosity function from semi-analytic models of galaxy formation. Cooling time > t H. Benson et al. 2003.

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The Faintest Dwarf Galaxies in Groups and Poor Clusters

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  1. The Faintest Dwarf Galaxies in Groups and Poor Clusters R. Marzke & A. Danielson (SFSU) M. Hudson (U. Waterloo) R. Windhorst (ASU) 1

  2. Supernova feedback, photoionization Galaxy luminosity function from semi-analytic models of galaxy formation Cooling time > tH Benson et al. 2003 K-band LFs from Cole et al. 2001, Kochanek et al. 2001, Huang et al. 2002 2

  3. Feedback Dekel & Silk 1986 3

  4. Chemical Enrichment Luminosity-metallicity relation for spheroidal galaxies Dekel & Silk 1986 4

  5. The field galaxy luminosity function Norberg et al. 2002 2dF Galaxy Redshift Survey 5

  6. Rich cluster LFs measured by statistical background subtraction Beijersbergen et al. 2002 6

  7. Spectroscopic measurement of the rich cluster LF Christlein & Zabludoff 2003 7

  8. The luminosity function in a more representative environment Little is known about the faintest dwarfs beyond the Local Group Armandroff, Jacoby & Davies 1999 8

  9. At 100 Mpc, the faintest Local Group dwarfs would have apparent magnitudes B~26 Needles in a haystack 9

  10. 10

  11. Not all dwarfs are diffuse Ultra-compact dwarfs in the Fornax cluster Drinkwater et al. 2003 11

  12. Drinkwater et al. 2003 12

  13. Crude redshifts improve background rejection dramatically Multislit spectroscopy can be efficient after preliminary photometric redshift filtering 13

  14. UBVRI BATC Photometric redshifts S/N=20 S/N=10 At low redshift, UV filters are critical but expensive S/N=5 14

  15. Measuring the LF down to globular cluster luminosities: Uncertainty in Statistical Background Subtraction Simulated observations of rich clusters No redshift information Photometric redshift filtering (UBVRI) Coma cluster, density decreased by 2,5,10 15

  16. Wavelength Xia et al. 2002 BATC filter set 16

  17. UBVRI BATC Photometric redshifts S/N=20 S/N=10 For the faintest LSB dwarfs, spectroscopic redshifts will be out of reach S/N=5 17

  18. The Survey • MKW/AWM clusters: CTIO 4m (BTC pilot survey) • Lower density environment than rich clusters • Higher merger probability • How do galaxy interactions affect the LF? • CfA/SSRS2 groups: MMT Megacam • Most common galaxy environment • Local-Group counterparts • Is the faint end of the Local-Group LF representative? • Photometric calibration: WIYN 0.9m + Mosaic • Spectroscopy: Magellan/IMACS 18

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