The Evolution of Stars and Gas

in Galaxies

PhD Thesis Proposal

Philip Lah

Supervisor: Frank Briggs

Supervisory Panel:

• Erwin de Blok (RSAA)

• Jayaram Chengalur (National Centre for Radio Astrophysics, India)

• Matthew Colless (Anglo-Australian Observatory)

• Roberto De Propris (University of Bristol, UK)

Goal of PhD

• to relate the evolution in galaxies of their star formation rate, their stellar mass and their mass of neutral hydrogen gas (the fuel of star formation)

• examine galaxy evolution over last 4 Gyr (going back third age of the universe)

• study galaxies in a variety of different environments

• UNIQUE PART study galaxy properties in same systems – optically selected galaxies

Why do this?

Should give a clearer picture of how, when and where stars and their host galaxies form.

Improves our understanding of our place in the universe, residing in our galaxy, the Milky Way, and orbiting our star, the Sun.

Background

Star Formation Rate

SubaruField

Hα Spectroscopy

Hα Narrow Band Imaging

UV (with no dust correction)

Stellar Mass Density

Dickenson et al. 2003

Neutral Hydrogen Gas Mass

Neutral Hydrogen Gas Mass

HIPASSHI 21cm

Rao & Turnshek

2003

Storrie-Lombardi

& Wolfe 2000

Galaxy Environment

galaxy environment cluster, cluster outskirts and the field

• density - morphology relation

• density - star formation relation

• density - neutral hydrogen relation

Cause of density relations?

HI 21cm Emission at

High Redshift

Previous highest redshift HI

Westerbork Synthesis Radio Telescope (WSRT)

Netherlands

Abell 2218 z = 0.18

integration time 36 days, Zwaan et al. 2001

Very Large Array (VLA)

Abell 2192 z = 0.1887

integration time ~80 hours, Veheijen et al. 2004

Giant Metrewave Radio Telescope

Giant Metrewave Radio Telescope

Giant Metrewave Radio Telescope

Giant Metrewave Radio Telescope

Giant Metrewave Radio Telescope

Giant Metrewave Radio Telescope

Giant Metrewave Radio Telescope

Giant Metrewave Radio Telescope

Giant Metrewave Radio Telescope

GMRT Antenna Positions

GMRT Collecting Area

30 dishes of 45 m diameter

GMRT Collecting Area

21 × ATCA

15 × Parkes

6.9 × WSRT

3.6 × VLA

Method of HI Detection

• individual galaxies HI 21cm emission below radio observational detection limits

• large sample of galaxies with known positions & precise redshifts (from optical observations)

• coadd weak HI signals isolated in position & redshift (velocity) space

• measure integrated HI signal – total HI mass of whole galaxy population – can calculate the average HI galaxy mass

Observational Targets

Table of Targets

Target zLook Back Time

νHIGMRT Obs

Time

Subaru Field

0.24 2.8 Gyr 1142 MHz 90 hours

Abell 370 0.37 4.0 Gyr 1033 MHz 70 hours

Cl0024+1654 0.39 4.2 Gyr 1022 MHz18 + 45 hours

Galaxy Cluster Abell 370

RA

DEC 27’ × 27’

Cluster Centre

Galaxy Cluster Abell 370

RA

DEC ~3’ × 3’

Abell 370 Data

• 42 literature redshifts for Abell 370 cluster members 33 are usable – large error in σz ≥ ± 300 kms-1 (from Soucail et al. 1988 )

• obtaining imaging data ESO 2.2m/WFI with VRI filters 34’ × 33’ (queue scheduled by Sept) use to select sample for spectroscopic follow-up

• using AF2/WYFFOS 4.2m William Herschel Telescope, La Palma (sometime in Oct to Dec) for redshifts and star formation rate from [OII]

Radio Data Cube

RA

DEC

Spectrum through Cubegalaxy redshift

Spectrum around Redshiftgalaxy redshift

Flux around Galaxy in Velocity Space

galaxy redshift

HI Abell 370

RMS decrease

Mass HI

Assuming an optically thin neutral hydrogen cloud

1

2

1

236

kms

V

Mpc

d

mJy

S

zM

M LHI

MHI* = 6.2 ×109 M (Zwaan et al. 2003)

Abell 370 HI Mass

No. Redshifts

HI Mass Upper Limit

(with 95% certainty)

33 8.0 × 109 M 1.3 MHI

*

Estimates:

100 2.5 × 109 M 0.42 MHI

*

300 1.7 × 109 M 0.28 MHI*

Galaxy Cluster Cl0024+1654

RA

DEC 21’ × 21’

Cluster Centre

Galaxy Cluster Cl0024+1654

RA

DEC ~1’ × 1’

Cl0024+1654 Data

• HST imaging 2181 galaxies with morphologies of which 195 spectroscopically confirmed cluster members (Treu et al. 2003)

• Hα narrow band imaging with Subaru star formation rates (Kodama et al. 2004)

• 296 literature redshifts within HI frequency limits of the GMRT observation (Cszoke et al. 2001)

• estimated HI Mass Upper Limit similar to Abell 370: ~1.7 × 109 M

Subaru Field

RA

DEC

24’ × 30’

Subaru Field Redshifts

Subaru Filter

FWHM (120 Å)

GMRT HI Freq Range

Subaru Field Redshifts

No. Redshifts

Estimated HI Mass Upper Limit

(with 95% certainty)

166 3.1 × 108 M 0.052 MHI

*

number of target Hα emitting galaxies = 347

number of galaxies with quality ≥ 3 redshifts = 183

number of galaxies in GMRT HI freq range = 166

Past and Future Work

Previous Workstarted PhD 1st March 2004

• Mar to mid-July 1st Three Month Project - preliminary work on reducing Abell 370 GMRT data - creating data reduction pipeline

• mid-July to Aug completed reduction of one sideband of the 7 days of data - prepared results for a GMRT telescope proposal for galaxy cluster Cl0024+1652

• Sept to mid-Nov 2nd Three Month Project - 6dFGS working with Robert Proctor and Duncan Forbes (Swinburne University) and Matthew Colless (AAO)

Previous Work

• mid Nov to Dec Literature Review for Thesis Proposal

• Jan 2005 traveled to India for GMRT observations galaxy cluster Cl0024+1652

• beginning of March 5 nights 2dF AAT redshift observations of the Subaru Field

• have been working on adapting and revising data reduction code for all GMRT data sets – developing partially automated flagging of data

Future Work

rest 2005:

• finish data reduction code

• reduce Subaru data and publish results

• reduce Cl0024+1652 data and publish results

• Abell 370 spectroscopic observations using AF2/WYFFOS 4.2m William Herschel Telescope, La Palma (sometime in Oct to Dec) – for redshifts and star formation rate from [OII]

Future Work2006:

• beginning year finish reducing Abell 370 data and publish results

• once published Subaru results may go back to GMRT TAC for another sample of field galaxies

• other possibilities:

- obtain more redshifts for coadding particularly on the outskirts of the clusters

- stellar mass measurements using redshifts and additional near-infrared imaging

Future Work

2007:

• first 6 months - finish write up thesis / finish off anything left over from previous years

The End

Additional Slides

The UV Plane

Abell 370 UV plane

UV Plane

GMRT Beam