The Science Case for Band 1

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The Science Case for Band 1

• James Di Francesco
• Herzberg Institute of Astrophysics
• Victoria, BC, Canada

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Band 1 - what is it?
Science Case for Band 1
350 mm
1
2
5
10
4
8
9 mm

• one of the 10 original bands intended for ALMA
• specs 31.3 - 45 GHz, TRx 17-28 K, USB, HEMT
  design
• removed in early 2000s during to save
  construction costs

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Can Band 1 be restored?
Science Case for Band 1

• ALMA post-construction development plan,
  involves community, new directions
• workshop held in Victoria, BC on 8-10 October
  2008 to revisit the Band 1 science case
• Band 1 enriches ALMA science at other bands,
  extends ALMA science to new regimes

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CO from High-Z galaxies
Science Case for Band 1

• molecular gas now detected at Z 6, eg., SDSS
  J11485251 at VLA, IRAM (Walter et al. 2003)
• CO data reveal excitation kinematics of early
  star and galaxy formation
• ALMA Band 1 receivers could detect CO (2-1) from
  galaxies at Z 4-6 and CO (3-2) from galaxies at
  Z 6-10

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CO from High-Z galaxies
Science Case for Band 1

• molecular gas now detected at Z 6, eg., SDSS
  J11485251 at VLA, IRAM (Walter et al. 2003)
• CO data reveal excitation kinematics of early
  star and galaxy formation
• ALMA Band 1 receivers could detect CO (2-1) from
  galaxies at Z 4-6 and CO (3-2) from galaxies at
  Z 6-10

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CO from High-Z galaxies
Science Case for Band 1
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Sunyaev-Zeldovich Effect
Science Case for Band 1

• hot electrons in galaxy clusters scatter CMB
  emission to higher energies, make holes in CMB
  at some frequencies
• SZE dependent on pressure, independent of
  redshift, used to derive Ho, baryon fraction,
  cluster morphology

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Sunyaev-Zeldovich Effect
Science Case for Band 1

• ALMA Band 1 will reveal substructure in
  clusters, eg., shocks from recent mergers,
  eliminate systematics from low-res obs.
• could also begin to probe SZE in individual
  galaxies (giant Es), explore AGN/SMBH feedback
  and galaxy density profiles (DM)

John Carlstrom
3 ?K rms in 22
15 ?K rms in 10
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Dust in Protoplanetary Disks
Science Case for Band 1
ISM

• protostars can be surrounded by accretion disks
  of gas and dust, the birthplaces of planets
• cool disk dust emits thermal radiation in
  proportion to its opacity, ???? ???
• opacity is related to grain size distribution
  and composition

30 ?m
??2
Adams et al. 1988, following Draine Lee 1984
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Dust in Protoplanetary Disks
Science Case for Band 1
ISM

• protostars can be surrounded by accretion disks
  of gas and dust, the birthplaces of planets
• cool disk dust emits thermal radiation in
  proportion to its opacity, ???? ???
• opacity is related to grain size distribution
  and composition

30 ?m
??2
Adams et al. 1988, following Draine Lee 1984
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Dust in Protoplanetary Disks
Science Case for Band 1
?0.7?0.1
Calvet et al. 2002

• spectral energy distributions of young stars can
  reveal grain growth from ISM dust, towards planet
  formation?
• since Band 1 samples longer wavelengths, it
  samples larger grains and provides longer lever
  arm to SEDs (departures?)
• free-free emission may be a problem, need lower
  ? too

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Radio Supernovae
Science Case for Band 1

• SNe radio lightcurves reveal density profiles of
  ejecta and circumstellar medium (CSM)
• SNe images show structure and size of shell,
  deceleration, geometric distance from expanding
  shock front method
• Can also search for stellar remnant of
  explosion, ie., the pulsar wind nebula (PWN)

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Radio Supernovae
Science Case for Band 1

• SNe radio lightcurves reveal density profiles of
  ejecta and circumstellar medium (CSM)
• SNe images show structure and size of shell,
  deceleration, geometric distance from expanding
  shock front method
• Can also search for stellar remnant of
  explosion, ie., the pulsar wind nebula (PWN)

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Radio Supernovae
Science Case for Band 1

• Band 1 radio SNe lightcurves, study galactic
  factories, rates, search for stellar remnants
• SN1987A 0.12 FWHM, expect 300 beams across
  shell in 2014, get 1001 dynamic range in 12 h
• VLBI at 43 GHz with ALMA and VLA/VLBA/GBT, good
  uv coverage for low-dec sources, Sgr A, lots of
  AGN, SNe?

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Radio Supernovae
Science Case for Band 1

• Band 1 radio SNe lightcurves, study galactic
  factories, rates, search for stellar remnants
• SN1987A 0.12 FWHM, expect 300 beams across
  shell in 2014, get 1001 dynamic range in 12 h
• VLBI at 43 GHz with ALMA and VLA/VLBA/GBT, good
  uv coverage for low-dec sources, Sgr A, lots of
  AGN, SNe?

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and more!
Science Case for Band 1

• debris disks
• chemistry of heavy organic species,
  carbon-chains, anions
• free-free emission from jets/outflows
• measuring B-field using Zeeman effect (CCS)
• spinning dust grains
• dust chemistry in AGB envelopes
• masers

We are working on a detailed Band 1 Science Case
document to distribute online to the community.
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ALMA band 1 vs. EVLA Q-band
Science Case for Band 1
EVLA
ALMA
Band 1 FIGHT!!!
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ALMA band 1 vs. EVLA Q-band
Science Case for Band 1

• ALMA and EVLA have, to first order, the same
  sensitivity at 31-45 GHz 1 ??rms 1 ?Jy in 12
  hours
• ALMA advantages few weather restrictions,
  greater no. of baselines (imaging quality), wider
  FOV (SZE/debris disks), southern hemisphere
• EVLA advantages finer spectral resolution
  (correlator), longer baselines, already in VLBA,
  northern hemisphere
• A careful comparison between EVLA and ALMA is
  needed to determine how often Band 1/Q-band can
  be observed!

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Summary and Final Points
Science Case for Band 1

• Band 1 would add 31-45 GHz capability to ALMA,
  perhaps extend to 50 GHz?
• Strong science cases exist for Band 1, that
  enhance or extend ALMA capabilities
• Band 1 is relatively inexpensive, 10-20M,
  depending on design
• relationship with EVLA needs to be carefully
  addressed
• input from community needed, please contact me
  if you wish to contribute!

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Science Case for Band 1
james.difrancesco_at_nrc-cnrc.gc.ca