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

2. Outline Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey2 Exploring the Stellar Populations ?? of Early-Type Galaxies ?? in the 6dF Galaxy Survey ??

3. What is the 6dF Galaxy Survey? one sentence answer g A spectroscopic survey of nearby galaxies across the entire southern sky. Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey3

4. 6dF 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 2MASS NIR J, H & K and SuperCOSMOS Sky Survey optical B & R magnitudes and images Contour Plot of 6dF Galaxy Distribution Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey4

5. Good Spectrum ~ 44 S/N per Å Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey5

6. What are Early-Type Galaxies? and the related question What are Late-Type Galaxies? Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey6

7. Early & Late Type Galaxies Early-Type elliptical & lenticular (S0) no evidence of HII emission regions: no H  or [OIII] emission & have H  absorption dominated by old stars with no recent star formation Late-Type spiral & irregular evidence of HII emission regions: H , [OIII] & H  emission mixture old & young stars, ongoing star formation Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey7

8. 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 Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey8

9. 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:  Worthey (1994) – standard model  Vazedekis (1996) – addresses issue of Horizontal Branch Stars  Thomas (2002) – includes non-solar abundances (various [  /Fe], [  /Ca] and [  /N]) Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey9

10. Lick Indices Mg b Lick Indices are a standardised way of measuring the equivalent width of a line Mg b Blue band pass 5142.625Å to 5161.375Å Central bandpass 5160.125Å to 5192.625Å Red Bandpass 5191.375Å to 5206.375Å Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey10

11. Lick Indices Lick indices defined in 1972 by Faber et al. wavelengths 4000-6200Å at ~8.6Å FWHM resolution Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey11

12. H  G vs [MgFe] Age vs Metallicity Grid from Worthey model data from Stephen Moore thesis (2001) 87 galaxies in the Coma cluster Moores MgFe Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey12

13. What I am doing? I am measuring various Lick indices in a sample of early-type galaxies from the 6dF Galaxy Survey. Then I am analysing the results using the three stellar population models getting ages of star formation and metallicites for the galaxies. What am I doing? Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey13

14. Why I am 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) Comparison of elliptical and lenticular (S0) galaxies: soggggggme previously found lenticulars younger than ellipticals fffffffffffff (Kuntschner 2000) & (Moore thesis 2001) Comparison of the different stellar population models: sofffffffffff new Thomas 2002 model with non-solar abundances to the older models Why am I doing this? Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey14

15. 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  used to calculate an error in z (  z=0.0001596  v=47.8 kms -1 )  comparing two values of a Lick index & the error measured by indexf from the repeat observations Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey15

16. My MgFe My preliminary H  G vs [MgFe] Of ~1100 galaxies only 12 on plot No [OIII] emission High Signal to Noise  Not broadened to Lick FWHM ~8.5Å  Not velocity dispersion corrected  Not remove galaxies with H  emission Philip Lah, Honours StudentExploring the Stellar Populations of Early-Type Galaxies in the 6dF Galaxy Survey16

17. The End