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Anomalous Emission from Dust in HII Regions

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					Anomalous Emission from
   Dust in HII Regions
        Student : Nikta Amiri
     Supervisors: Prof. Rod Davies
                  Prof. Peter Wilkinson

               October 2007
            Overview
Galactic foregrounds
Anomalous emission from dust
CBI Instrument
Analysis and results
   Galactic Foregrounds
To understand the Cosmic Microwave Background
Radiation, Galactic Foregrounds must be accurately
known over a wide frequency range.


Galactic Emission
 consists of:
- Synchrotron
- Free-Free
- Dust




                              (Watson et al. 2005)
Anomalous Emission From Dust

A new component of Galactic Foregrounds in the
frequency range 10-60 GHz (Kogut et al.1996)

It was originally thought that this emission is due to
either Synchrotron or Free-Free emission (Leitch et
al.1997)


The most probable interpretation
is the Spinning Dust Paradigm
(Draine   & Lazarian 1998)
   What type of Dust is anomalous?
  Small Grains containing between 10-1000 atoms

  The Microwave Emission
  from these grains is
  related to the electric
  dipole moment

  Predicted Emission




(Draine & Lazarian 1998)
           Observational Evidence
- Davies et al.2006 used the WMAP (Wilkinson Microwave Anisotropy Probe) data to
work on the three galactic foregrounds .15 regions of the sky were selected. The
 selection of the fields was based on the fact that one of the three foregrounds is
 dominant in each field.

- Significant amounts of anomalous emission associated wit dust
were found in most of the 15 regions




 full-sky map showing the
 15 selected regions in red




                                                   Davies et al.2006
            Observational Evidence




        Region 6 among all other fields shows a close correlation between K
                              band and dust images




Davies et al.2006
              The Instrument
13 90-cm Cassegrain
antennas
 – 78 baselines

10 1 GHz channels 26-36
GHz

Field-of-view 44 arcmin

Resolution 4.5 – 10 arcmin
 Anomalous Emission from Dust
       in HII REGIONS
Free-free emission from hot electrons (7000 - 8000 K)
dominates these regions at radio frequencies

These regions contain significant amounts of dust with
the strongest far infrared (FIR) emission in the Galaxy.
Dust temperatures in HII Regions
are higher than the general ISM
        (Davies et al. 2006)
                      Map obtained from the
                    Cosmic Background Imager
                         Observations
-Observations of several bright
HII regions were made
with the CBI on 20 June 2005

- The peak flux density is 24.7
  Jy/beam
-The synthesized beam is
  5.67 * 5.65 arc min

-The astronomical data reduction
packages DS9 and AIPS are
being used to calibrate and edit
 the data from the CBI

          CLEANed CBI (31GHz)
         map of the G333-0.5 region
          which contains several      Supplied by Dr. Clive Dickinson
           discrete bright objects
IRAS 100 m grey scale map of G333-0.5
               Free-Free Spectrum of G333.6-0.2
-The expected value for the CBI is 66.1 ± 6.61 Jy
- The CBI measured value is 95.39 ± 2.57 Jy
- The excess emission is 33% of the total flux density




                                                                α = -0.12
G333.6-0.2


                                                         CBI
                                                          CBI
    Free-Free Spectrum of G333.3-0.4

-The expected value for the CBI is 27.00 ± 8.91 Jy
- The CBI measured value is Jy 30.10 ± 2.25
- The excess emission is 2.90 ± 9.10
- The upper limit of the excess emission is 18.2 Jy




                 G333.3-0.4


                                                      CBI
     Free-Free Spectrum of G333.1-0.4
- The CBI measured value is 74.66 ± 0.79 Jy
- The expected value for the CBI is 66.23 ± 6.60 Jy
-The excess emission is 8.43 ± 6.70 Jy
- The upper limit of the excess emission is 13.4 Jy




                G333.1-0.4                            CBI
Anomalous Dust Emissivity

				
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posted:7/29/2011
language:English
pages:16