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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

dn * ( x) = = (ln 10) x d (log x)

+1 - x

e

where

x=M
Zwaan et al. 97:
3 * = 0.0048h70 log M * / M sun = 9.86 - 2 в log h70 = -1.20

HI

/M

*

Rosenberg & Schneider 02:
3 * = 0.0041h70 log M * / M sun = 9.94 - 2 в log h70

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

= -1.53


Source-to-beam extent

Integration time in sec

Signal width in km


· 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 Model 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 second


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...]