Anomalous emission from HII regions

1. Anomalous emission from HII regions Clive Dickinson (IPAC/Caltech)

2. Introduction Anomalous emission appears to be �real� I.e. not regular synchrotron, free-free, thermal dust (see Rod Davies review talk) Could be �spinning dust� or other mechanism? (hot free-free, cold dust, magnetic dust, fullarenes�.) Detections from �compact� Galactic objects in �HII regions� Perseus G159.6-18.5, RCW175, others? HII regions often associated with lots of dust Stars form in molecular clouds Dust heated to T~30-50K typically

3. Spinning dust models Draine & Lazarian (1998a,b) spinning dust models are currently the best explanation but tweaking required! See Yacine Ali-Hamoud poster Grain with dipole moment ? at angular velocity ? radiates power:- -> Small grains spinning very fast! (a<10-7cm for >10GHz) Explains correlation with dust, and narrow spectrum between ~10-60GHz Remarkably, the emissivity does not change by more than a factor of a few!

4. Spinning dust cloud in Perseus

5. LPH[96]201.166+1.6 HII cloud observed to have rising spectrum between 5-10GHz (Finkbeiner et al. 2002,2004) Lower frequency Effelsberg data (1.4/2.7GHz) & CBI 31GHz data consistent with optically thin free-free (?~-2.1). ?=-2.12 (Dickinson et al. 2003) allows up to a maximum ~20% of anomalous emission at 31 GHz but is consistent with free-free alone. Very narrow frequency range for spinning dust. No significant polarization detected (<few %). Finkbeiner Green Bank data likely to be spurious (Finkbeiner, priv. comm.)

6. Southern HII regions CBI observations of 6 bright HII regions Tentative evidence for excess emission at 31GHz based on optically thin free-free model G284.3-0.3 (RCW49) most significant Average dust �emissivity� lower than high latitude values by factor of >3 No significant polarization (<1%)

7. More HII regions AMI observed sample of 16 HII regions at 14-17GHz (Scaife et al. 2008) No significant evidence for �excess� emission Radio �emissivity� w.r.t. 100?m <1?K/(MJy/sr) for many of the sample Small grain destruction? 3 objects possibly with ~10 ?K/(MJy/sr) See Keith Grainge�s talk

8. VSA Galactic surveys

9. RCW175 with CBI2 Re-observed RCW175 HII region with CBI2 see James Allison�s talk for more details 31GHz (26-36GHz) 4arcmin resolution Good u,v coverage 5-15arcmins scales are well sampled

10. RCW175 excess emission confirmed! WMAP 94GHz upper limit Not optically thick free-free (e.g. UCHII region) Not cold dust or flat dust emissivity No bright extragalacitc (GPS) sources -> Best explanation is spinning dust Emissivity consistent with Draine & Lazarian (1998) models high latitude values (e.g. Davies et al. 2006)

11. 3C396 �Dusty� supernova remnant Excess emission at 33GHz with VSA. RRLs suggest not free-free

12. Conclusions Significant evidence for anomalous dust emission at Galactic high latitudes and also in some dust/HII clouds. HII regions may be some of the best places to look for spinning dust Why some but not others? Physics of the dust and different environments? RCW175 is another example of probable spinning dust emission ~3Jy (50% of total) of spinning dust Emissivity consistent with Draine & Lazarian models and high-latitudes More data required in this area! 10-100GHz Low and high resolution (diffuse vs compact emission) Accurate calibration! Planck will do a lot for us! (But still need 5-25GHz & higher resolutions) See Richard Davis poster (anomalous emission with Planck) See Marta Alves poster (RRLs survey)