Maarten Baes

Attenuation of starlight in Virgo Cluster galaxies

HeViCS consortium meeting, Garching bei München, 8-9 April 2013

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.

Fraction of Ldust to Ltot

Major result based on IRAS bright galaxies: Ldust is about 30% of Ltot

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 Ldust/Ltot

• Virgo sample uses ISOPHOT data out to 200 µm: traces also the cool dust luminosity not traced by IRAS

HeViCS study of attenuation

We can do much better now thanks to HeViCS

• Sample: we can create larger and better sampleso FIR/submm selected sample (based on BGS or Planck)o optically selected sample (VCC)

• Much more reliable data to determine both Ltot and Ldust: 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 Ldust/Ltot: determine at which wavelengths dust absorbs most energy (UV or optical ?)

MagPhys example

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

Maarten Baes

Attenuation of starlight in Virgo Cluster galaxies

HeViCS consortium meeting, Garching bei München, 8-9 April 2013