1. Matthew.Smith@astro.cf.ac.uk

2.  SPIRE/PACS guaranteed time programme.  Parallel Mode Observations at 100, 160, 250, 350 and 500µm simultaneously.  Each half 1cross-scan, 18.2 hours  Complementary XMM  Results shown on BBC TV

3. R. GendlerESA/Herschel/PACS/SPIRE/J.Fritz, U.GentESA/XMM-Newton/EPIC/W.Pietsch, MPE

4. ESA Press Release

6.  Cardiff Source Extraction Software  Run by Jason Kirk  S/N > 7.5σ

7. Spiral Model from Gordon et al. 2006

8.  HELGA is not just for PR  M31 is the nearest and closest Milky Way like(?) Giant Spiral Galaxy.  Can study at high resolutions at all wavelengths.  Today describe some of our first results (Smith et al. in prep, Fritz et al in prep).

10.  Use 5 Herschel bands & 70µm MIPS as upper limit.  Images smoothed to 500µm resolution and re-gridded to 36" pixels (~500µm beam size)  Only taken pixels with all 6 fluxes > 5σ  Still have 4000 pixels!  Use 20% PACS error and 7% SPIRE error (correlated)

11.  Fit modified blackbody:  Find need for a variable β  Take into account filter profile and correlated uncertainties in SED fitter Flux(ν) = Mass dust × κ ν × B(ν,T) / Dist 2 Mass-Opacity Coefficient α ν β

12.  All pixels are fitted well by a modified blackbody.

13.  No evidence for a cold dust component (<13 K), that has been found in some Dwarf galaxies (Madden et al. SAG2) Dust Temperature ~ 10K Low metallicity dwarf galaxy (1/3 solar)

15.  Calculated using method Leroy et al. 2008  Uses linear combination of 24µm and FUV emission.  Foreground stars removed using NUV to FUV ratio  Emission due to old stellar population removed using 3.6µm map of M31. (using correction factors derived in ellipticals where SF is assumed to have ceased)

16.  Dust is correlated with SFR, not old stellar population.

17.  Gas-to-dust ratio fits exponential profile  Gradient = 0.05 dex kpc -1  Metallicity gradient -0.06 ± 0.03 dex kpc -1  Can trace metals with dust.

18.  Strong increase in the centre bulge  Fairly flat in ring/spiral structures.  Range of 15 to 35K

19.  Above threshold 3.6µm is correlated with Temperature.  Gradient consistent with Flux α T 6  What is heating rest of the dust?

20.  In contrast to new M83 results (Foyle et al. in prep) where T is correlated to SFR – using similar analysis.  Bendo et al. (In press) suggested emission >100µm is heated by old stars, while <70µm is heated by Star-Formation.  Many pixels show 70µm excess which could be a population heated by SF – need another data point to know.

21.  Change in β around 3.5kpc  β = ~1.8 in main ring is in good agreement with Planck early results.  >5kpc, β decreases while T is ~constant

22.  Possible correlation with β and 3.6µm, much more so than seen with Temperature, below threshold.

23.  Theoretical B/T inverse relationship in dust properties.  Also B/T fitting degeneracy  Simulation suggest if error in fitted parameter then correlated, but average accurate.  Cannot explain trends with other properties.

24.  Planck Result MW

25.  Re-create analysis from Planck early results  Still work in progress...  As Planck was only looking in the local environment of the MW we have to adjust for radial gas-to-dust change (equivalently metallicity gradient)

27.  Produce map of optical depth / N H corrected for radial enhancement.  Have regions of enhancement.

28.  Same analysis for Andromeda might not work as:  M31 has a very low CO fraction (ie vast majority pixels are > 95% dominated by HI mass  Looking through whole disk so getting an average result.  How can we get round these issues?  Compare average τ / N H result with those from IRAS.  Put in proposal to map areas of M31 in [CII] with Herschel – targeting most suggestive areas.

29.  HELGA gives a complete census of dust in our nearest Milky-Way like object.  β and T do vary within a galaxy.  Currently no indications of “dark-gas”, but the same Planck method may not be appropriate. Thank You for Listening