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Using the EVLA to Extend Studies of Baryons in the Local Universe to Higher Redshift

Using the EVLA to Extend Studies of Baryons in the Local Universe to Higher Redshift. Jessica L. Rosenberg George Mason University. Collaborators: Andrew West, Lisa Horne, Preston Zeh, ALFALFA team lead by Giovanelli and Haynes. Combining SDSS and ALFALFA to Study Baryons in the Local Universe.

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Using the EVLA to Extend Studies of Baryons in the Local Universe to Higher Redshift

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  1. Using the EVLA to Extend Studies of Baryons in the Local Universe to Higher Redshift Jessica L. Rosenberg George Mason University Collaborators: Andrew West, Lisa Horne, Preston Zeh, ALFALFA team lead by Giovanelli and Haynes

  2. Combining SDSS and ALFALFA to Study Baryons in the Local Universe 30 300 60 180 -30 Northern Virgo “Region 2” • ~4000 deg2 of overlap • 30,000+ galaxies in the final sample • Samples a wide range of galaxy environment • Selecting SDSS galaxies from spectroscopic sample • Most ALFALFA galaxies not in the spectroscopic sample will have SDSS photometric information

  3. 30 300 60 180 -30 Northern Virgo “Region 2” Combining SDSS and ALFALFA to Study Baryons in the Local Universe • Beginning with 2 small regions for which data are presently available • 926 galaxies in total • Samples different environments • Useful for testing SDSS photometry, ALFALFA upper limits, etc.

  4. SDSS ALFALFA • 2.5m telescope • u, g, r, i, z optical bands • spectroscopy for >675,000 galaxies • >8000 deg2 of sky • 120x106 pixels, >600 slits/field • 305m telescope • spectroscopy for >30,000 galaxies • survey limit of cz=18,000 km/s • ~7000 deg2 of sky • 7 “pixels”

  5. Why study gas and stars in galaxies?i.e. Why bother combining SDSS & ALFALFA in a common volume? • Most previous studies have selected galaxies by stars OR gas - this is the first time you can do both • Selecting galaxies by both gas and stars provides the most unbiased view • -CDM models predict the baryons in galaxies. The fraction in gas and stars is dependent on astrophysics • Note that the molecular component is missing so it is not ALL baryons • The relationship between gas, stars, (dark matter) provides information on astrophysics

  6. Early heating of the Universe The luminosity and the HI mass functions help constrain models The HI+stellar mass function would provide a better constraint Mo et al. 2005

  7. “Astrophysics”:What drives the gas-to-stars ratio in galaxies • What environment has the largest impact on galaxy properties? • Is the impact of environment a large scale effect or a small scale effect? • Are neighbors, groups, or clusters the most effective/responsible for the impact on galaxies? • What is the most important, tidal interactions, ram pressure stripping, galaxy harassment?

  8. ALFALFA + SDSS SDSS only ALFALFA only Selecting galaxies by their gas AND stars allows for the detection of a diverse set of objects

  9. Galaxy Distributions in ALFALFA/SDSS sub-regions Northern Virgo Region 2 * ALFALFA sources  SDSS sources Sample different environments even in these small regions

  10. Statistics from the Sub-regions

  11. dVirgo = 1.7 vel = -170 km/s Log(Mstar) = 13.98

  12. dVirgo = 6.0 vel = 7594 km/s Log(Mstar) = 13.98

  13. Log(Mstar) = 13.98

  14. dVirgo = 16.4 vel = 6857 km/s Log(Mstar) = 13.98

  15. Log(Mstar) = 13.98

  16. Summary • This survey will teach us a tremendous amount about the baryon content of local galaxies • We will be able to examine the relationship between environment and the baryonic properties of galaxies • We will have the least biased view of the baryonic components of galaxies to date • But… it is only a z=0 constraint on galaxy evolution

  17. Using EVLA to study baryons at higher z • Study the change in baryon distribution over time and environment • Most detectable galaxies will be identified in other surveys • EVLA will provide imaging capability and resolution • Can map the continuum as well as the lines • Targeted samples favor more strongly star-forming systems • Can we get deep enough over enough area to diversify the sample by including a deep, blind, HI study?

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