ALFALFA Graduate Student Project

Proposal Title: Star formation in isolated galaxies
Student Name: Oded Spector
Adviser: Noah Brosch
Context: Part of Ph.D. thesis
Institution: Tel-Aviv University
Time frame: 2007--
Other collaborators: Martha Haynes, Riccardo Giovanelli
Publication expected? yes, 2008+


The goal of this research is the study star formation behavior in "test lab" conditions, i.e. in isolated galaxies which have not been significantly affected in their recent histories by outside influence. Isolated dwarf galaxies will be of special interest, since they lack some star formation effects that are common in spirals. Since the effects of the galaxies' HI content on star formation will be examined, galaxies with a range of HI content, as wide as possible, will be selected.

Galaxy isolation will be determined by searching NED, AGC and possibly some other databases, for neighboring galaxies. The criteria for determining a galaxy's isolation, will be defined such that there will be a low probability for it to have close encountered another galaxy in the last few Giga years. These criteria will be devised and tested theoretically, possibly using the Millennium simulation.

The main sources of data will be the Wise Observatory, and ALFALFA. Data collected in Wise will include imaging in the rest-frame Hα line emission, and in the wide bands (U, B, V, R and I). ALFALFA data that will be used includes total HI contents, red-shifts, and HI line profiles.

Star formation rates (SFR) will be derived from measurements of Hα. Star formation histories will be estimated by comparing color-color diagrams with theoretical models of evolutionary synthesis of galaxies. For each sufficiently bright galaxy, morphological features will be obtained. Specifically, HII regions will be identified and their individual SFR values will be derived.

Results will be analyzed as functions of galaxy properties such as HI content, velocity profile and morphological type. The results will be further compared to those of earlier researches, namely Elchanan Almoznino's and Ana B. Heller's dissertations on Virgo cluster dwarf galaxies, and published papers on similar topics. This comparison will attempt to reveal the dependence of star formation properties on the galaxies' neighborhood.

ALFALFA region:All available regions
ALFALFA data to be used: Catalog datasets: total HI content, redshifts, line profiles
Other data sets to be used:
  1. Optical imaging in rest frame α and in U,B,V,R, and I bands from Wise 1m.
  2. AGC, NED, and possibly other galaxy datbases
  3. The Millennium simulation
Products to be delivered:
  1. Catalog of isolated galaxies (including a theoretically justified selection algorithm).
  2. Database of star formation properties of isolated galaxies.

First Hα measurementsAt the Wise Observatory Mar 2007 
Isolation criteriaTheoretical justification Summer 2007in progress
Catalog of isolated galaxies   Fall 2007in progress
Star formation propertiesFull catalog of the sample 2009  

This page created and maintained by members of the Cornell ExtraGalactic Group

Last modified: Mon Mar 24 09:09:33 EDT 2008 by martha