Extragalactic hi surveys with the feed array
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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

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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

  • 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


A few useful scaling laws…


Beam dilution

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


Survey simulation ingredients…


HIMF

where

Zwaan et al. 97:

Rosenberg & Schneider 02:

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


Source-to-beam extent

Integration time in sec

Signal width in km/s


  • 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


  • 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


Slice of the cosmic

Density field along

The Supergalactic

Plane

You are here


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?


  • 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


6 seconds


6 seconds


ZOA

300 sec

|b| < 10

AO limits


ZOA

300 sec

|b| < 10

AO limits


ZOA

300 sec

|b| < 10

AO limits


Virgo

11h-13h RA

0 to 27 Dec

60 sec

800 hours


What about synergies?


What about synergies?


1 second


1 second

1 second


3 seconds


3 seconds


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


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