Exploring the Stellar Populations of EarlyType Galaxies in

Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah Honours Student h Supervisors: Matthew Colless Heath Jones

Exploring the Stellar Populations ? ? of Outline Early-Type Galaxies ? ? in the 6 d. F Galaxy Survey ? ? Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 2

What is the 6 d. F Galaxy Survey? one sentence answer g A spectroscopic survey of nearby galaxies across the entire southern sky. Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 3

6 d. F Galaxy Survey • targets are near infrared selected (K band) • started mid 2001; to end mid 2005; the first public data release was Dec 2002 • 13, 000 V & R spectra with redshifts; peak z~0. 05 (~200 Mpc) • also have 2 MASS NIR J, H & K and Super. COSMOS Sky Survey optical B & R magnitudes and images Contour Plot of 6 d. F Galaxy Distribution Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 4

Good Spectrum ~ 44 S/N per Å Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 5

What are Early-Type Galaxies? and the related question What are Late-Type Galaxies? Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 6

Early-Type Late-Type Early & Late Type Galaxies • elliptical & lenticular (S 0) • spiral & irregular • no evidence of HII emission regions: no H or [OIII] emission & have H absorption • evidence of HII emission regions: H , [OIII] & H emission • dominated by old stars with no recent star formation • mixture old & young stars, ongoing star formation Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 7

Why the interest in the stellar population? The only significant contributor to the light from early-type galaxies is the starlight g Use stellar population models to measure the ages and metallicites of the galaxies Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 8

Stellar Population Models • models assume single burst of star formation – all stars same age – similar to globular cluster • input age of star formation & metallicity into the models – generate lists Lick indices, colours & magnitudes 3 stellar population models: Ø Worthey (1994) – standard model Ø Vazedekis (1996) – addresses issue of Horizontal Branch Stars Ø Thomas (2002) – includes non-solar abundances (various [ /Fe], [ /Ca] and [ /N]) Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 9

Lick Indices Mgb Lick Indices are a standardised way of measuring the equivalent width of a line Mgb Blue band pass 5142. 625Å to 5161. 375Å Central bandpass 5160. 125Å to 5192. 625Å Red Bandpass 5191. 375Å to 5206. 375Å Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 10

Lick Indices • Lick indices defined in 1972 by Faber et al. • wavelengths 4000 -6200Å at ~8. 6Å FWHM resolution Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 11

H G vs [Mg. Fe] Moores Mg. Fe • Age vs Metallicity Grid from Worthey model • data from Stephen Moore thesis (2001) 87 galaxies in the Coma cluster Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 12

What am I doing? I am measuring various Lick indices in a sample of early-type galaxies from the 6 d. F Galaxy Survey. What I am doing? Then I am analysing the results using the three stellar population models getting ages of star formation and metallicites for the galaxies. Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 13

Why am I doing this? To learn more about the formation of early-type galaxies in different environments. Comparison of the properties of field and cluster galaxies: sddffff • expect field galaxies have same metallicity but are younger those in clusters (Kauffmann & Charlot 1998) Why I am doing this? Comparison of elliptical and lenticular (S 0) galaxies: soggggggme • previously found lenticulars younger than ellipticals fffffff (Kuntschner 2000) & (Moore thesis 2001) Comparison of the different stellar population models: soffffff • new Thomas 2002 model with non-solar abundances to the older models Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 14

My Work to Date • using program indexf that measures Lick indices & gives errors • using a Perl script to automate the process – measuring many different indices for many galaxies • I have solved problems of lines redshifted into R spectrum & negative points in Lick bandpasses • my current sample ~1100 galaxies – repeat observations with quality=4 Ø used to calculate an error in z ( z=0. 0001596 v=47. 8 kms-1) Ø comparing two values of a Lick index & the error measured by indexf from the repeat observations Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 15

My preliminary H G vs [Mg. Fe] Of ~1100 galaxies only 12 on plot • No [OIII] emission • High Signal to Noise My Mg. Fe Ø Not broadened to Lick FWHM ~8. 5Å Ø Not velocity dispersion corrected Ø Not remove galaxies with H emission Exploring the Stellar Populations of Early-Type Galaxies in the 6 d. F Galaxy Survey Philip Lah, Honours Student 16

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