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									The Dust Properties
of Galactic HII Regions
as seen by Herschel




     Loren Anderson
     Laboratoire d'Astrophysique de Marseille

     Annie Zavagno, Javier Rodon, Lise Deharveng,
     and the “HOBYS” and “Evolution of Interstellar Dust” consortia
     Special thanks to Helene Roussel for help with data processing


Loren Anderson          Great Barriers in High Mass Star Formation   September 15, 2010
                              Motivation
Dust temperatures/emissivities:
→ Are necessary for accurate column density & mass calculations
→ Are much less well-known compared to the gas temperature
→ Tell us about the dust grain population

HII region are unique laboratories with star formation in various stages, all
at the same distance from the Sun

HII regions with a “bubble” morphology have a well-defined PDRs, simple
geometries
→ Roughly half of all Galactic HII regions have a bubble morphology
(Anderson et al. 2010, in prep., from the GBT HII Region Survey)




 Loren Anderson         Great Barriers in High Mass Star Formation   September 15, 2010
      IRAS Color Temperatures of HII Regions
Crowther & Conti 2003,
Conti & Crowther 2004

Aperture photometry of UC and “giant”
HII regions (those with log(Nly) > 50)




Chan & Fich 1995

Aperture photometry of UC and
compact HII regions




    Loren Anderson       Great Barriers in High Mass Star Formation   September 15, 2010
                     Dust Temperatures in M17
Povich et al., 2007

Study of M17 with
2MASS, MSX, IRAC,
and IRAS from 1 to
100 μm



→ Interior aperture (R1)
peaks near 20μm
   → Tdust ≈ 100 K

→ PDR apertures (R2 &
R3) peak near 60μm
    → Tdust ≈ 40 K

                               Spitzer IRAC 5.8 μm IRAC 4.5μm IRAC 3.6μm
    Loren Anderson         Great Barriers in High Mass Star Formation   September 15, 2010
                       HII Region Sample




RCW120: D=1.3 kpc     RCW82: D=2.9 kpc




                                                      W5: D=2.0 kpc


Sh104: D=4.0 kpc       RCW79: D=4.2 kpc
      Herschel SPIRE 500 μm Herschel SPIRE 250 μm Herschel PACS 100 μm
    Loren Anderson       Great Barriers in High Mass Star Formation   September 15, 2010
                     HII Region Sample - RCW120




Herschel SPIRE 500 μm                               Spitzer GLIMPSE 8.0 μm
Herschel SPIRE 250 μm
Herschel PACS 100 μm
                see Zavagno et al., 2007, Deharveng et al., 2009, Martins et al., 2010, Zavagno
                et al., 2010, Anderson et al. 2010
    Loren Anderson             Great Barriers in High Mass Star Formation    September 15, 2010
                  HII Region Sample - Sh104




Herschel SPIRE 500 μm Herschel SPIRE 250 μm Herschel PACS 100 μm
                                   see Deharveng et al., 2003, Rodon et al., 2010

 Loren Anderson            Great Barriers in High Mass Star Formation   September 15, 2010
                     HII Region Sample - RCW79




Herschel SPIRE 500 μm                               Spitzer GLIMPSE 8.0 μm
Herschel SPIRE 250 μm
Herschel PACS 100 μm

                     see Cohen et al., 2002, Zavagno et al., 2006, Martins et al., 2010

    Loren Anderson             Great Barriers in High Mass Star Formation     September 15, 2010
                     HII Region Sample - RCW82




Herschel SPIRE 500 μm                          Spitzer GLIMPSE 8.0 μm
Herschel SPIRE 250 μm
Herschel PACS 100 μm

                                        see Pomares et al., 2009, Martins et al., 2010
    Loren Anderson        Great Barriers in High Mass Star Formation       September 15, 2010
                        HII Region Sample - W5




Herschel SPIRE 500 μm                           Spitzer 8.0 μm composite
Herschel SPIRE 250 μm
Herschel PACS 100 μm



    Loren Anderson         Great Barriers in High Mass Star Formation      September 15, 2010
             Dust Temperature Determination




                                                           RCW120 Anderson et al., 2010


1) Aperture photometry                         2) Temperature Maps

→ Get temperature and dust beta                → Get spatial distribution of dust
values for select regions of interest          temperatures at high angular
                                               resolution
→ Derived temperatures are
averages within the aperture                   → The fit quality per aperture (one
                                               pixel) is poor compared to that of the
→ Large-scale distribution of dust             aperture photometry
temperature values is unknown                      → The determination of β from
                                               this method is questionable

   Loren Anderson          Great Barriers in High Mass Star Formation             September 15, 2010
                         The β-T Relation




   Dupac et al., 2003                                           Desert et al., 2008




    Anderson et al., 2010 (RCW120)                      Rodon et al., 2010 (Sh104)



Loren Anderson            Great Barriers in High Mass Star Formation           September 15, 2010
                 Aperture Photometry




                                                # Along PDRs : 35
                                                   (11 are mm-condensations)
                                                # Filaments : 26
                                                # UC HII Regions : 5



Loren Anderson     Great Barriers in High Mass Star Formation   September 15, 2010
                           The β-T Relation




RCW120 (Anderson              RCW82
        et al., 2010)



                                                                        W5




S104 (Rodon et al, 2010)      RCW79
    Loren Anderson         Great Barriers in High Mass Star Formation        September 15, 2010
                 The β-T Relation




Loren Anderson   Great Barriers in High Mass Star Formation   September 15, 2010
                       The β-T Relation




   Filaments                                        PDR




   PDR Condensations                                Entire Field


Loren Anderson         Great Barriers in High Mass Star Formation   September 15, 2010
                           Is it Real???




Derived T and β-values given input T from 10 to 40 K and β=2.5
→ For dust spanning a range of temperatures, we cannot derive a
  false β-T relationship
→ Derived values are evenly distributed about input β, T
                                                                    see also Shetty et al., 2009
  Loren Anderson       Great Barriers in High Mass Star Formation            September 15, 2010
                    Dust Temperature Maps




RCW120               RCW82




                                                     W5

Sh104                RCW79

   Loren Anderson      Great Barriers in High Mass Star Formation   September 15, 2010
   But, there is a hotter component too....
Herschel SPIRE 250 μm Herschel PACS 100 μm Spitzer MIPS 24 μm




    RCW120 Anderson et al., 2010                  NGC 7023-E PDR Abergel et al., 2010
Loren Anderson           Great Barriers in High Mass Star Formation       September 15, 2010
                          Conclusions
Dust properties:
 → PDRs: 20-25, β~2
  → Filaments: 15-20, β~2 (~10K, β~3 for IRDCs)

  → The “interior” of HII regions coincident with the ionized

   gas has warmer dust though

We find strong evidence for a β-T relation, both for individual
HII regions, and also for the entire sample of HII regions
  The β-T relation cannot be explained by the effects of noise

   or calibration uncertainty




  Loren Anderson     Great Barriers in High Mass Star Formation   September 15, 2010

								
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