1. Maarten Baes Attenuation of starlight in Virgo Cluster galaxies HeViCS consortium meeting, Garching bei München, 8-9 April 2013

2. Dust extinction We want to know how much radiation is attenuated by interstellar dust in galaxies at every wavelength Important for correcting observed fluxes and converting them to intrinsic luminosities Dust extinction is the key to understanding the heating sources of the dust question (important e.g. for the use of FIR emission as a tool to estimate the SFR) Shape of the extinction curve can tell us something on the composition and size distribution of dust grains in different environments.

3. Fraction of L dust to L tot Major result based on IRAS bright galaxies: L dust is about 30% of L tot Study of 28 late-type galaxies with ISOPHOT by Popescu & Tuffs (2002): same result (but with a spread in Hubble type) Two effects that work in opposite sense: IRAS bright galaxies were selected as FIR luminous sources: you would expect a higher value of L dust /L tot Virgo sample uses ISOPHOT data out to 200 µm: traces also the cool dust luminosity not traced by IRAS

4. HeViCS study of attenuation We can do much better now thanks to HeViCS Sample: we can create larger and better samples o FIR/submm selected sample (based on BGS or Planck) o optically selected sample (VCC) Much more reliable data to determine both L tot and L dust : panchromatic combination of GALEX, SDSS, UKIDSS/2MASS, WISE, (Spitzer), Herschel Interesting option: MagPhys (self-consistent modelling of the UV/optical/NIR and MIR/FIR/submm emission using energy balance arguments) We can do more than just calculate L dust /L tot : determine at which wavelengths dust absorbs most energy (UV or optical ?)

5. MagPhys example

7. Action plan Step 1: determine suitable samples (optically selected and FIR/submm selected) Step 2: collect panchromatic data sets PACS/SPIRE: in hand SDSS/GALEX: from Luca’s HRS paper (+ add missing) 2MASS/UKIDSS: from archive ? WISE: from archive ? Step 3: MagPhys modelling – Sébastien/Ilse are experienced users… Step 4: analysis and interpretation

8. Maarten Baes Attenuation of starlight in Virgo Cluster galaxies HeViCS consortium meeting, Garching bei München, 8-9 April 2013