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Overview of CMB foreground observations
Clive DickinsonJodrell Bank Centre for Astrophysics (JBCA)
University of Manchester, U.K.
Understanding Galactic & extragalactic foregrounds, Zadar, Croatia, 23-27 May 2011
Tuesday, 24 May 2011
• Foregrounds = everything after redshift of 1100 (or ~6)!
• Foregrounds are interesting for precise CMB cosmology and in their own right!
CMB (and EoR) are behind a lot of stuff!
Planck
Tuesday, 24 May 2011
Foreground componentsName Description Frequencies (GHz) How do we study it/remove it?
Synchrotron Relativistic electrons in B-field <30 Radio surveys & γ-rays
Free-free Electrons accelerated in ionized gas <100 Radio surveys, recombination lines
Anomalous Probably electric dipole radiation from small spinning dust grains 10-100 Microwave surveys
Thermal dust Blackbody radiation from warm dust(T~10-30 K) >100 Sub-mm/IR surveys & UV/optical
Radio sources Synchrotron emission from AGN <150 High resolution radio surveys
Dusty galaxies Dust emission from dusty galaxies >150 High resolution sub-mm/IR surveys
CIB Integrated dust from high z galaxies >100 High resolution sub-mm/IR surveys
SZ (clusters) Inverse Compton scattering of CMB photons off hot electrons in IGM 10-300 High resolution CMB surveys
Zodiacal light Dust emission from solar system cloud >100 Sub-mm/IR surveys
Line contamination Atomic & molecular lines (e.g. CO) Various Spectroscopic surveys/split bands
RFI Man-made interference(e.g. GPS, radar, CCTV) Various! (esp. radio) Surveys, filtering, low sidelobes/go into space!
Atmosphere Blackbody radiation, H20, O2 broad line emission All Surveys, filtering, high altitude/go into space!
Ground Blackbody radiation spillover All Low sidelobes/go into space!
... ... ... ???
Tuesday, 24 May 2011
• CMB + ancillary data are required
• Wide range of frequencies
• ~1 GHz to ~5000 GHz
• Lots of frequency channels
• Total intensity & full polarization
• Spectroscopy (Hα, RRLs, CO, HI...)
• High resolution data: diffuse maps & source surveys
• (Local surveys for RFI, atmosphere etc. )
What observations are required?IRAS WHAM
e-VLAGBT
WMAP Parkes
Tuesday, 24 May 2011
CMB/foreground observations have improved a lot!
COBE-DMR(Bennett et al. 1994)
Planck HFI maps - CMB removed(Planck collaboration; arXiv:1101.2048)
100 GHz
857 GHz
353 GHz
143 GHz
545 GHz
217 GHz
Tuesday, 24 May 2011
Foregrounds are interesting!
• See this conference!
• 25 Planck early results papers submitted to A&A (special issue) on 11th Jan 2011
• Early release compact source catalogue (ERCSC) (see Chen talk)
• 7 product papers
• 5 SZ/cluster papers (see Aghanim talk)
• 6 Extragalactic papers (see Chen talk)
• 7 Galactic/solar system papers
Tuesday, 24 May 2011
Overview of Planck early papers in the Galaxy
• Cold clumps (arXiv:1101.2035 & arXiv:1101.2034)
• 915 of cold (T~7-17 K) cores/clumps/clouds!
• High latitude dust (arXiv:1101.2036)
• Comparing Planck dust with HI & IRAS: dust emissivity, temperature, CIB...
• Molecular clouds (arXiv:1101.2037)
• Temperature, spectral index (β=1.78), optical depth of nearby mol clouds.
• Dark gas (arXiv:1101.2039)
• All-sky temperature, optical depth: emission not correlated with HI/CO (probably H2)
• Significant discussion of Anomalous Microwave Emission (AME):-
• New Light on Anomalous Microwave Emission from Spinning Dust Grains (arXiv:1101.2031)
• Properties of the interstellar medium in the Galactic Plane (arXiv:1101.2032)
• Origin of the submm excess dust emission in the Magellanic Clouds (arXiv:1101.2046)
Tuesday, 24 May 2011
• Nature has been kind to CMB cosmologists!
• CMB window ~30-200 GHz
• TT not too bad, except at small scales
• Need deep source surveys for modelling (see Dunkley & Jarvis talks)
Intensity foregrounds
Dunkley et al. (2010)
WMAP Ka-band (33 GHz)
Bennett et al. (2003)
Tuesday, 24 May 2011
Full sky templates
Haslam et al. 408 MHz
Synchrotron: Low-frequency radio surveys
Hα all-sky compilations(Dickinson et al. 2003; Finkbeiner 2003)
Free-free: Recombination lines
IRAS/DIRBE extrapolation(Finkbeiner, Davis, Schlegel 1999)
Thermal dust and AME:Far Infrared
Tuesday, 24 May 2011
• The eye, and power spectra, not very sensitive to low-level residuals!
Modelling foreground components
Dickinson et al. (2009)
Tuesday, 24 May 2011
Radio surveys
de Oliveira-Costa et al. (2008)
Tuesday, 24 May 2011
• Spectral index required for extrapolation from radio
• Not known accurately above ~1 GHz
• β=~-2.0 to -4.0, typically -2.7 to -3.2 (<β>~-3.0)
• Curvature above 5 GHz?
• WMAP “haze”: β~-2.5
• Explain high-latitude AME? (Bennett et al. 2003)
• Need “high” frequency radio data (~5-20 GHz)
Synchrotron spectral index
WMAP Haze (courtesy Rajib Saha & JPL group (c. 2007)(see Finkbeiner 2003, 2004 etc.)
WMAP 7-yr synch spectral index (Gold et al. 2011)
Curvature of synchrotron in radio sources(courtesy Paddy Leahy)
Tuesday, 24 May 2011
• Synchrotron/free-free difficult to separate using spectrum alone
• β~-3.0 vs -2.1
• Hα has allowed free-free to be measured independently (if Te known)
• Both depend on EM
• Long-standing issue on scattered light - 5-10% or 50%?
Free-free templates via Hα surveysDickinson et al. (2003)
WHAM+VTSS (Finkbeiner 2003)Witt et al. (2010)
!
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2dl#
Tuesday, 24 May 2011
WHAM
Haffner et al. (2003)
Wisconsin H-Alpha Mapper (WHAM)Almost completed the Southern Survey
Tuesday, 24 May 2011
• ~Full-sky maps not easy to make! (see Reich/Haverkorn talks)
• Many problems (for all frequencies!)
• Sensitivity/spatial coverage
• Zero-levels/spatial coverage
• Calibration
• Contamination from “other” sources
• e.g. atmosphere
• e.g. stars, radio galaxies, Zodiacal light
• e.g. stray light
• e.g. RFI
• Often not in full polarisation
• New data are needed! (e.g. S-PASS, C-BASS etc.)
Maps not as good as they first appear!NCP at 408 MHz
(destriped/desourced Haslam et al. map)
ECP at Hα(WHAM)
Tuesday, 24 May 2011
• Hα not reliable near the plane
• RRLs can do this!
• e.g. re-analysis of HIPASS survey
• But signals are weak!
• Also measure Te, velocity etc.
RRL surveys
Alves et al. (2010)
Tuesday, 24 May 2011
• Thermal emission from dust grains at T~10-30 K
• Important above ~100 GHz
• Data mostly from IR/FIR
• IRAS (12, 25, 60, 100 um) & DIRBE (esp 100, 140, 240 um)
• Very complicated subject! (dust composition, sizes, temperatures)
• Spectrum approximated as a modified blackbody υβxB(υ, T) where β~2.0
• Finkbeiner, Davis, Schlegel (1999)
• 2-component dust model with β=+1.7 at low frequencies
• This will not do for Planck! (ok for WMAP)
Thermal dust emission
IRAS/DIRBE extrapolation(Finkbeiner, Davis, Schlegel 1999)
Original IRAS surveys
Tuesday, 24 May 2011
• AME has been seen almost everywhere!
• Correlated with FIR (dust)
• ~10-60 GHz
• Probably electric dipole radiation from small spinning dust grains (Draine & Lazarian 1998)
• Peaked spectrum
• Shape depends on dust properties & environment
• Lots of interest!
• See talks by Lazarian, Hoang, Tibbs, Todorivic...
Anomalous Microwave Emission
Draine & Lazarian (1998) models. See also Ali-Hamoud et al. (2009), Silsbee et al. (2010), Hoang et al. (2010,2011)
Adapted from Leitch et al. (1997)
Tuesday, 24 May 2011
A bit of history...
Tuesday, 24 May 2011
Observational evidence for AME
A lot of evidence over the last 14 years - very active area of research, but still little is known about it! (lack of data!)Many papers, instruments, techniques, frequency ranges. E.g.:-
OVRO: Leitch et al. (1997)COBE-DMR: Kogut et al. (1996), Banday et al. (2003)Saskatoon: de Oliveira-Costa (1997)Tenerife: Mukherjee et al. (2001), de Oliveira-Costa et al. (2002, 2004)Python V: Mukherjee et al. (2003)Green Bank: Finkbeiner (2002), Finkbeiner et al. (2004)Cosmosomas: Watson et al. (2005), Battistelli et al. (2006), Hildebrandt et al. (2007)VSA: Scaife et al. (2007), Tibbs et al. (2009), Todorovic et al. (2010)CBI: Casassus et al. (2004,2006,2007,2008), Dickinson et al. (2006,2007,2009a,2010), Castellanos et al. (2011), Vidal et al. (2011)AMI: Scaife et al. (2008), Scaife et al. (2009a,b), Scaife et al. (2010)WMAP: Bennett et al. (2003), Lagache et al. (2003), Davies et al. (2006), Bonaldi et al. (2007), Miville-Deschenes et al. (2008), Gold et al. (2009,2010), Dobler & Finkbeiner (2009), Ysard et al. (2009), Dickinson et al. (2009a), Lopez-Caraballo (2011)Planck: Planck collaboration (2011)& now extragalactic as well! (Murphy et al. 2010; Scaife et al. 2010)
Tuesday, 24 May 2011
• Need to understand AME better and test spinning dust model
• Diffuse high latitude foregrounds vs Galactic objects
AME observations are important!
CBI 31 GHz correlation with Spitzer IRAC/MIPS(Casassus et al. 2008)
AMI 15 GHz correlation with IRAC 8um(Scaife et al. 2010)
Tuesday, 24 May 2011
• Perseus cloud: most precise spectrum of AME to-date
• Looks very much like spinning dust!
• Physically-motivated spectrum can provide a very good fit
Planck AME spectrum
Planck collaboration (arXiv: 1101.2031)
Tuesday, 24 May 2011
But it is not quite so simple...
LDN1780: Expected clear difference between 12/25 (PAHs/small grains) & 60/100 (large grains) CBI 31 GHz contours most closely correlated with 60 micron data
(Vidal et al. 2011)
Tuesday, 24 May 2011
• Nature probably not so kind! (unless r~0.1 or bigger!)
• Very little data at relevant frequencies (above ~5 GHz)
• Polarized sources not so bad?
• Few % for radio sources (Battye et al. 2011)
• ~1% or below for IR dusty galaxies (Seiffert et al. 2007)
Polarized foregrounds
Page et al. (2007)
B-modes @ upper limit!(r<0.17)
Measured foregrounds!
Tuesday, 24 May 2011
• Free-free expected to be unpolarised
• AME appears to have low polarisation if any (Battistelli et al. 2006; Kogut et al. 2007; Dickinson et al. 2007; Mason et al. 2009; Lopez-Caraballo et al. 2011)
• Synchrotron up to ~75%
• Very few measurements at Faraday-free frequencies (above about 5 GHz)
• WMAP: 5-50% (Kogut et al. 2007)
• Thermal dust has been measured up to ~35% in some clouds
• Expect ~5-10% at high latitudes
• Agrees with Archeops (Ponthieu et al. 2005)
Polarized foregrounds - synchrotron & dust
BICEP @ 100, 150, 220 GHz(Bierman et al. 2011)
Tuesday, 24 May 2011
• Unprecedented sensitivity and frequency coverage coming online
• eVLA, ATCA, GBT, ALMA, SKA...
• Also S-PASS and others...(see Haverkorn talk)
• Planck!
• 30-857 GHz (available early 2013)
• Polarized dust (e.g. 353 GHz)
• Specialised telescopes look promising for large angular scales
• e.g. C-BASS (see Pearson talk and Stevenson poster)
• QUIJOTE, COFE, PILOT...
• Future CMB polarization satellite? (COrE, CMBpol...?)
What do we have to look forward to?
QUIJOTE (Tenerife): 11-19 GHz
C-BASS (California & South Africa): 5 GHz
Tuesday, 24 May 2011
• Foregrounds are important for CMB and EoR
• 1. Must understand & characterise them to be able to remove them accurately for cosmology
• Polarization more difficult!
• 2. They are interesting in their own right! (e.g. Galactic/extragalactic astrophysics)
• We need more data!
• Radio surveys, sub-mm/far-IR, optical data, CO etc.
• Special need for high frequency polarization data!
• Lots to learn in both cosmology and Galactic/extragalactic astrophysics!
Conclusions
Watch out for more Planck results in the near future!
Tuesday, 24 May 2011
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