continuum:continuum:flux integrated over a range flux integrated over a range in wavelengthin wavelength

line: spectral resolution (Petitpas et al.)

Whitmore et al

HST850μm

Continuum Observing in the Submm/mmTracy Webb (McGill)

how do we make continuum measurements?

some specific physics we can measure

examples of recent continuum science

Next 40 mins ...

what is the submm/mm?

generally defined as: 200m-1mm “submillimeter” 1mm - 10mm “millimeter”

shorter wavelengths mid-far-infraredlonger wavelengths cm and radio

sources of submm/mm radiation

thermal emission -- cold dust and CMB synchrotron -- relativistic electrons in SNR free-free (Bremstrahlung) -- ionized gas (inverse compton scattering -- SZ clusters)

these mechanisms are generally associated with structure formation physics, young objects, and optically obscured regions

why work in the submm/mm continuum?

technology just becoming mature ‘breakthrough’ science still possible JCMT-SCUBA citation rate rivals HST!

> 1/2 the total energy in the cosmic background

science areas for continuum work:

- debris/proto-planetary disks- Galactic star formation regions- ISM in local galaxies- high-redshift galaxy formation- high-redshift clusters - SZ effect- CMB cosmology

1996 UKT14 1 pixel2007 SCUBA2 104 pixels!

limited by the atmosphere:what wavelengths are possible from the ground?

350µm450µm

750µm850µm

facilities:single-dish &interferometers

JCMT

Submillimeter Array

Detectors and Receivers: Bolometer

Arrays

Transition Edge Sensorsfast, linear response, sensitive

Incoming photons drive change in T and therefore change in R. Signal is read as voltage or current.

used on single dish detectors provide wide bandwidth can be wide-field multi-pixel

SCUBA

SCUBA-2

(to scale)

(not to scale)

Detectors and Receivers: heterodynes

IF = RF - LO

IF = RF + LO

preserves phase and spectral information useful for line and continuum work

single dish and arrays small bandwidth 1-2 GHz single or very few pixels

RF amplifier

tunable local oscillator

mixer IF amplifier further

analysis/detectionelectronics

EMR

antenna

collapse over wavelengthto form image

Neri et al.

creating a continuum maptwo basic and almost universal problems (cf SCUBA2):

need to remove the sky: absorption, emission, noise H20 molecular transitions, thermal emission, changing temporally +spatially

arrays usually under sample the sky and heterodynes areoften only one pixel

A B C

measures differences in fluxthrows: 30-120 arcsecfrequency: many Hz

sky skysource

“chop and nod” mapping

scan mapsjiggle maps

throw

a comparison of some submm continuum facilities

ground based

JCMT 15m SCUBA2 450µm/850µm 104 pixels NorthernCSO 10m SHARC-II 350µm 384 pixels NorthernApex 12m LaBoca 870µm 295 pixels SouthernLMT 50m AzTec 1.1mm/2.1mm 144 pixels SouthernIRAM 30m MAMBO-2 1.2mm 117 pixels Northern

airborne observatories

BLAST 2m 250µm -500µm SOFIA 2.5m 0.3µm -1.3mmHerschel 3.5m 60µm-700µm

interferometersSMA 8x6m HawaiiIRAM PdB 5 x 15m FranceCARMA California (BIMA+OVRO) 6x10m + 10x6mALMA (not yet operational) see later talk

submm emission: thermal radiation from cold dust

T = 10-100K dust peaks at 30µm-300µm

peaks where the atmosphere isopaque but still substantial flux in the submm (especially when redshifted)

T=3K (CMB) peaks at 1mm

Wien’s displacement law:

never a simple single-temperature Black Body

small grains: < 0.1µm in sizenot in thermal equalibrium with the interstellar radiation field (ISRF) but are heated stochasticallymost of the time very cold, but spike to 100-1000K

large grains:>0.1 µm in sizein thermal equalibrium with ISRFgenerally 10-100K

dust temperature depends on heating mechanism and distribution:star formation, active galactic nucleus, old starscompact hot dust vs diffuse cold dust

emissivity (emission efficiency) where ~1-2thermal spectrum becomes S B(T)

hot dense cores in Orion

cold diffuse Galactic dust

‘secondary’ sources of emission

synchrotron

free-free

thermal

CO line contaminationfrom molecular gas

relativistic electrons in supernova remnants ionized gas

these processes are often found together!dust = gas = star formation = supernovae/hard radiation field

specific constraints provided by continuum measurements

dust temperature(Dunne et al. 2002)

Md = S850 D2/(d() B(T))

distance emissivityflux density

dust mass(Hildebrand 1983)assuming optically thin dust

star formation rate (Bell 2003)

(LTIR estimated from fitting SED to FIR/submm)

debris disks - extra-solar (proto) planetary systemscold disks of dust debris around stars

Holland et al.

star forming regions in the Galaxy: sites of obscured star formation in the Eagle nebula

HST image450µm with SCUBAWhite et al. 1999

the mass function of cold dusty clumps

consistent with aSalpeter initialmass function!

(Reid & Wilson)

continuum emission from supernova remnants

.

Dunne et al. 2004Dwek et al. 2004

evidence for dust in supernovae -- process of dust production at high redshift (ie z~6)?

Ultraluminous IR Galaxies (ULIRGs)

the most luminous systems are also the dustiest and the most IR/submm bright -- 90% of their energy is emitted in the FIR/submm

galaxy models of Silva et al.blue - no dust starburstred - dust added

Sanders & Mirabel review

850m contours over optical images

Whitmore et al

spatial correlation between optical/UVand FIR/submm?

multi-temperature components multi-dust components dust mass estimates ...

(Dunne et al. 2002; Wilson et al. 2004)

what can we learn about nearby galaxies?

high redshift galaxies: the advantage of the K-correction

850μmredshift 1-9

at long wavelengths FIR-bright galaxies do not getfainter as they get further away!

high-resolution submm imaging:Iono et al. 2006submm and UV emitting regions are different

filamentary structure on 400kpc scales around z=2 QSOStevens et al. 2005

submm source counts: Scott et al. 2002orders of magnitude evolution from z=0-3

no evolution

ALMA

SCUBA2

galaxy clusters and the Sunyaev-Zel’dovich effect: probes of cosmology

Carlstrom et al.

SZ facilities: Apex-SZ (Chile), ACBAR (South Pole)CBI (Chile), DASI (South Pole), ACT (Chile) ... SCUBA2?

hot electrons in intracluster gas inverse compton scatterbackground CMB photons tohigher energies

decrease in CMB intensity

increase in CMBintensity

and of course the CMB!

the future of continuum observing in the submm(i.e. is there anything left to learn?)

we have be limited by large beams, low sensitivity,slow mapping speed- no longer.

large scale structure and statistical astronomyGovernato et al. 1998

dusty starbursts with HST in the opticalALMA has similar resolution in the submm!

25 nights with SCUBA

2 nights 2ith SCUBA2

z~0 z~1

z > 2