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Extragalactic HI Surveys with the Feed Array. Riccardo Giovanelli Cornell University. Main Scientific Goals: Investigate the faint end of the HI mass function (HIMF) Determine the local density dependence of the HIMF Map the distribution of luminous and dark matter

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extragalactic hi surveys with the feed array

Extragalactic HI Surveys with the Feed Array

Riccardo Giovanelli

Cornell University

slide2

Main Scientific Goals:

  • Investigate the faint end of the HI mass function
  • (HIMF)
  • Determine the local density dependence of the HIMF
  • Map the distribution of luminous and dark matter
  • in the local (z < 0.1) Universe
  • Determine the gas-rich membership of nearby
  • groups of galaxies
  • Determine the population of gas-rich systems in the
  • Local Group and the periphery of the MW (HVCs)
  • Find (rare) OH Megamasers near z=0.25
  • Be surprised
slide4

Beam dilution

[by comparison, HIPASS detects 1 million solar masses at 1 Mpc in 460 sec…]

slide8

HIMF

where

Zwaan et al. 97:

Rosenberg & Schneider 02:

[Mpc**-3 dex**-1]

slide9

Source-to-beam extent

Integration time in sec

Signal width in km/s

slide10

The reliability of a detection depends on S/N.

  • Model the probability p, that a “detection” at given S/N
  • will be confirmed, as
  • Model W_kms as Gauss deviate with dispersion 0.1 dex about

scramble disk inclination and add turbulent term

  • Model source size as
slide11

Simulate random pointing errors and estimate

  • beam dilution factor
  • Model suppression of gas infall onto low mass
  • halos due to reionization (e.g. adopting the
  • “filtering mass” criterion of Gnedin & Hui 1998)

Next,

adopt a model for the cosmic density field

slide12

Slice of the cosmic

Density field along

The Supergalactic

Plane

You are here

slide13

Where are the

Low HI mass

Systems?

Normalized Cosmic Density

  • Most of the mass is to be found in regions of density
  • substantially higher than average

Caveat:

But, do low baryonic mass systems trace the cosmic

density distribution?

slide14

A set of survey simulations:

  • All-AO, fast (6-sec) sky survey:
  • ALFALFA
  • 300 - sec ZOA ``staring’’ survey
  • ZOA
  • 60 - sec Virgo Cluster survey
  • VIRGO
slide17

ZOA

300 sec

|b| < 10

AO limits

slide18

ZOA

300 sec

|b| < 10

AO limits

slide19

ZOA

300 sec

|b| < 10

AO limits

slide20

Virgo

11h-13h RA

0 to 27 Dec

60 sec

800 hours

slide24

1 second

1 second

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