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HST. 850 μ m. Whitmore et al. Continuum Observing in the Submm/mm Tracy Webb (McGill). continuum: flux integrated over a range in wavelength. line: spectral resolution (Petitpas et al.). Next 40 mins.  how do we make continuum measurements?  some specific physics we can measure

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Continuum flux integrated over a range in wavelength

HST

850μm

Whitmore et al

Continuum Observing in the Submm/mm

Tracy Webb (McGill)

continuum:

flux integrated over a range in wavelength

line: spectral resolution

(Petitpas et al.)


Continuum flux integrated over a range in wavelength

Next 40 mins ...

 how do we make continuum measurements?

 some specific physics we can measure

 examples of recent continuum science


Continuum flux integrated over a range in wavelength

what is the submm/mm?

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

1mm - 10mm “millimeter”

shorter wavelengths  mid-far-infrared

longer 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


Continuum flux integrated over a range in wavelength

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

1996 UKT14 1 pixel

2007 SCUBA2 104 pixels!

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


Continuum flux integrated over a range in wavelength

limited by the atmosphere:

what wavelengths are possible from the ground?

750µm

850µm

350µm

450µm


Continuum flux integrated over a range in wavelength

JCMT

facilities:

single-dish

&

interferometers

Submillimeter Array


Continuum flux integrated over a range in wavelength

Detectors and Receivers: Bolometer Arrays

(not to scale)

SCUBA

(to scale)

SCUBA-2

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

Transition Edge Sensors

fast, linear response, sensitive


Continuum flux integrated over a range in wavelength

EMR

antenna

IF

amplifier

RF

amplifier

further

analysis/detection

electronics

mixer

tunable

local

oscillator

Detectors and Receivers: heterodynes

collapse over wavelength

to form image

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

Neri et al.


Continuum flux integrated over a range in wavelength

jiggle maps

creating a continuum map

  • two 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 are

    often only one pixel

“chop and nod”

mapping

throw

A

B

C

source

sky

sky

measures differences in flux

throws: 30-120 arcsec

frequency: many Hz

scan maps


Continuum flux integrated over a range in wavelength

a comparison of some submm continuum facilities

ground based

JCMT 15m SCUBA2 450µm/850µm 104 pixels Northern

CSO 10m SHARC-II 350µm 384 pixels Northern

Apex 12m LaBoca 870µm 295 pixels Southern

LMT 50m AzTec 1.1mm/2.1mm 144 pixels Southern

IRAM 30m MAMBO-2 1.2mm 117 pixels Northern

airborne observatories

BLAST 2m 250µm -500µm

SOFIA 2.5m 0.3µm -1.3mm

Herschel 3.5m 60µm-700µm

interferometers

SMA 8x6m Hawaii

IRAM PdB 5 x 15m France

CARMA California (BIMA+OVRO) 6x10m + 10x6m

ALMA (not yet operational) see later talk


Continuum flux integrated over a range in wavelength

submm emission: thermal radiation from cold dust

T = 10-100K dust peaks at

30µm-300µm

peaks where the atmosphere is

opaque but still substantial flux

in the submm (especially when

redshifted)

T=3K (CMB) peaks at 1mm

Wien’s displacement law:


Continuum flux integrated over a range in wavelength

never a simple single-temperature Black Body

small grains:

< 0.1µm in size

not in thermal equalibrium with the interstellar radiation

field (ISRF) but are heated stochastically

most of the time very cold, but spike to 100-1000K

large grains:

>0.1 µm in size

in thermal equalibrium with ISRF

generally 10-100K

dust temperature depends on heating

mechanism and distribution:

star formation, active galactic nucleus, old stars

compact hot dust vs diffuse cold dust

emissivity (emission efficiency)   where ~1-2

thermal spectrum becomes S  B(T)

hot dense

cores in Orion

cold diffuse

Galactic dust


Continuum flux integrated over a range in wavelength

‘secondary’ sources of emission

thermal

synchrotron

free-free

 relativistic electrons in supernova remnants

 ionized gas

CO line contamination

from molecular gas

these processes are often found together!

dust = gas = star formation = supernovae/hard radiation field


Continuum flux integrated over a range in wavelength

specific constraints provided by continuum measurements

dust

temperature

(Dunne et al. 2002)

Md = S850 D2/(d() B(T))

dust mass

(Hildebrand 1983)

assuming optically thin dust

flux density

distance

emissivity

star formation

rate (Bell 2003)

(LTIR estimated from fitting SED to FIR/submm)


Continuum flux integrated over a range in wavelength

debris disks - extra-solar (proto) planetary systems

cold disks of dust debris around stars

Holland et al.


Continuum flux integrated over a range in wavelength

star forming regions in the Galaxy:

sites of obscured star formation in the Eagle nebula

450µm with SCUBA

White et al. 1999

HST image


Continuum flux integrated over a range in wavelength

the mass function of cold dusty clumps

consistent with a

Salpeter initial

mass function!

(Reid & Wilson)


Continuum flux integrated over a range in wavelength

continuum emission from supernova remnants

.

Dunne et al. 2004

Dwek et al. 2004

evidence for dust in supernovae

-- process of dust production at high redshift (ie z~6)?


Continuum flux integrated over a range in wavelength

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 starburst

red - dust added

Sanders & Mirabel review


Continuum flux integrated over a range in wavelength

Whitmore et al

what can we learn about nearby galaxies?

 spatial correlation between optical/UV

and FIR/submm?

 multi-temperature components

 multi-dust components

 dust mass estimates ...

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

850m contours over optical images


Continuum flux integrated over a range in wavelength

high redshift galaxies: the advantage of the K-correction

850μm

redshift 1-9

at long wavelengths FIR-bright galaxies do not get

fainter as they get further away!


Continuum flux integrated over a range in wavelength

ALMA

 high-resolution submm imaging:Iono et al. 2006

submm and UV emitting regions are different

no evolution

SCUBA2

 filamentary structure on 400kpc scales around z=2 QSO

Stevens et al. 2005

 submm source counts: Scott et al. 2002

orders of magnitude evolution from z=0-3


Continuum flux integrated over a range in wavelength

galaxy clusters and the Sunyaev-Zel’dovich effect:

probes of cosmology

decrease in CMB

intensity

increase in CMB

intensity

hot electrons in intracluster

gas inverse compton scatter

background CMB photons to

higher energies

Carlstrom et al.

SZ facilities: Apex-SZ (Chile), ACBAR (South Pole)

CBI (Chile), DASI (South Pole), ACT (Chile) ... SCUBA2?


Continuum flux integrated over a range in wavelength

and of course the CMB!


Continuum flux integrated over a range in wavelength

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.

25 nights with SCUBA

z~0

z~1

z > 2

2 nights 2ith SCUBA2

 dusty starbursts with HST in the optical

ALMA has similar resolution in the submm!

 large scale structure and statistical astronomy

Governato et al. 1998


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