Princeton University

Department of Astrophysical Sciences

Announces the

2008 Lyman Spitzer, Jr. Lecture Series



Martha Haynes
Cornell University



General Astronomy Colloquium*

Peyton Hall Auditorium

Tuesday, May 6, 2008

4:15 p.m.



HI Cosmology in the Local Universe with ALFALFA


The Arecibo Legacy Fast ALFA (ALFALFA) survey is an on-going second generation blind extragalactic HI survey exploiting 
Arecibo's superior sensitivity, angular resolution and digital technology to conduct a  census of the local HI universe 
over a cosmologically significant volume. When complete in 3-4 years, ALFALFA will detect some 30,000 extragalactic HI 
line sources out to z~0.06. Its catalog will be especially useful in synergy with wide area surveys conducted at other 
wavelengths. ALFALFA is detecting HI masses as low as 10**6  solar masses and as high as 10**10.8 solar masses with 
positional accuracies typically better than 20 arcsec, allowing immediate identification of the most probable optical 
counterpart to each HI detection. In the region of the Virgo Cluster of galaxies, a number of optically dark HI sources 
have been found. These all lie in the outskirts of the cluster and could be tidal or "harassment" debris, the result of 
high speed gravitational encounters. First ALFALFA  results already indicate, in agreement with the suggestions of  
previous, more limited studies, that there is not a cosmologically significant population of optically dark but HI rich 
galaxies. However, the majority of ALFALFA detections are too optically faint or of low surface brightness to have been 
included in previous targeted HI surveys. ALFALFA promises a wealthy dataset for the exploration of many issues in local
universe cosmology and galaxy evolution studies, setting the stage for future extension of these investigations to higher 
redshifts with the Square Kilometer Array.





Peyton Hall Auditorium


Lecture 1 - May 1st, 4:30 p.m.
The Importance of HI to the Gastrophysics of Galaxies
Lecture 2 - May 5th, 4:30 p.m. 
The Importance of Gas to the Evolution of Galaxies

Lecture 3 - May 8th, 4:30 p.m.
The Low-Mass End of the HI Mass Function:
Dwarf Galaxies, Void Galaxies and High Velocity Clouds




*Refreshments will be served immediately following the Colloquium in the Peyton Hall Reception Area