new overview of cmb foreground observations · 2011. 6. 22. · overview of cmb foreground...

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


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!

... ... ... ???


• 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


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


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


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)


• 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)


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


• The eye, and power spectra, not very sensitive to low-level residuals!

Modelling foreground components

Dickinson et al. (2009)


Radio surveys

de Oliveira-Costa et al. (2008)


• 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)


• 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#


WHAM

Haffner et al. (2003)

Wisconsin H-Alpha Mapper (WHAM)Almost completed the Southern Survey


• ~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)


• 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)


• 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


• 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)


A bit of history...


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)


• 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)


• 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)


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)


• 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!


• 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)


• 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


• 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!


new overview of cmb foreground observations · 2011. 6. 22. · overview of cmb foreground...

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