Extragalactic HI Extragalactic HI Surveys with the Feed Surveys with the Feed

ArrayArray

Riccardo GiovanelliRiccardo Giovanelli

Cornell UniversityCornell University

Main Scientific Goals:Main Scientific Goals:

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

A few useful scaling laws…A few useful scaling laws…

Beam dilutionBeam dilution

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

Survey simulation ingredients…Survey simulation ingredients…

xexxd

dnx 1*)10(ln

)(log)(

*/MMx HIwhere

Zwaan et al. 97: Zwaan et al. 97: Rosenberg & Schneider 02:Rosenberg & Schneider 02:370

* 0048.0 h 370

* 0041.0 h

70* log286.9/log hMM sun 70

* log294.9/log hMM sun 20.1 53.1

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

HIMFHIMF

Integration time in secIntegration time in secSource-to-beam extentSource-to-beam extent Signal width in km/sSignal width in km/s

• The The reliability reliability of a detection depends on S/N.of a detection depends on S/N. Model the probability Model the probability p,p, that a “detection” at given S/N that a “detection” at given S/N will be confirmed, aswill be confirmed, as

• Model W_kms as Gauss deviate with dispersion 0.1 dex aboutModel W_kms as Gauss deviate with dispersion 0.1 dex about

scramble disk inclination and add turbulent termscramble disk inclination and add turbulent term

• Model source size asModel source size as

• Simulate random pointing errors and estimate Simulate random pointing errors and estimate beam dilution factorbeam dilution factor

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

Next,Next,

adopt a model for the cosmic density fieldadopt a model for the cosmic density field

Slice of the cosmicSlice of the cosmicDensity field alongDensity field alongThe SupergalacticThe SupergalacticPlanePlane

You are hereYou are here

Normalized Cosmic DensityNormalized Cosmic Density

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

Caveat: Caveat: But, do low baryonic mass systems trace the cosmicdensity distribution?

Where are theWhere are theLow HI massLow HI massSystems?Systems?

A set of survey simulations:A set of survey simulations:

• All-AO, fast (6-sec) sky survey:All-AO, fast (6-sec) sky survey: ALFALFAALFALFA• 300 - sec ZOA ``staring’’ survey300 - sec ZOA ``staring’’ survey ZOAZOA• 60 - sec Virgo Cluster survey60 - sec Virgo Cluster survey VIRGOVIRGO

6 seconds6 seconds

6 seconds6 seconds

ZOAZOA

300 sec300 sec

|b| < 10|b| < 10

AO limitsAO limits

ZOAZOA

300 sec300 sec

|b| < 10|b| < 10

AO limitsAO limits

ZOAZOA

300 sec300 sec

|b| < 10|b| < 10

AO limitsAO limits

VirgoVirgo11h-13h RA11h-13h RA0 to 27 Dec0 to 27 Dec60 sec60 sec800 hours800 hours

What about synergies?What about synergies?

What about synergies?What about synergies?

1 second1 second

1 second1 second1 second1 second

3 seconds3 seconds

3 seconds3 seconds

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