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The Science Case for Band 1

The Science Case for Band 1. James Di Francesco Herzberg Institute of Astrophysics Victoria, BC, Canada. Science Case for Band 1. Band 1 - what is it?. 350 m m. 1. 2. 5. 10. 4. 8. 9 mm. one of the 10 original bands intended for ALMA

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The Science Case for Band 1

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  1. The Science Case for Band 1 James Di Francesco Herzberg Institute of Astrophysics Victoria, BC, Canada

  2. Science Case for Band 1 Band 1 - what is it? 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 2000’s during to save construction costs

  3. 1 3 2 8 5 7 10 9 6 1 4 ALMA receiver optics Science Case for Band 1 Can Band 1 be restored? • 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

  4. 1” J1148 CO (3-2) VLA Walter et al. 2004 Science Case for Band 1 CO from High-Z galaxies • molecular gas now detected at Z ~ 6, eg., SDSS J1148+5251 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

  5. Science Case for Band 1 CO from High-Z galaxies • molecular gas now detected at Z ~ 6, eg., SDSS J1148+5251 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

  6. Science Case for Band 1 CO from High-Z galaxies

  7. Science Case for Band 1 Sunyaev-Zel’dovich Effect • 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

  8. Science Case for Band 1 Sunyaev-Zel’dovich Effect • 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 ~15 K rms in 10” ~3 K rms in 22”

  9. T. Greene Science Case for Band 1 Dust in Protoplanetary Disks 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

  10. Science Case for Band 1 Dust in Protoplanetary Disks 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

  11. Science Case for Band 1 Dust in Protoplanetary Disks =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

  12. SN 1987A (epoch 2006.9) ATCA at 9 GHz (0.4” FWHM) Gaensler et al. (2007) Science Case for Band 1 Radio Supernovae • 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)

  13. SN 1986J Red: 5 GHz VLBI Blue/White: 15 GHz VLBI Bietenholz, Bartel & Rupen (2004) Science Case for Band 1 Radio Supernovae • 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)

  14. SN remnants in M82 McDonald et al. (2001) Science Case for Band 1 Radio Supernovae • 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 100:1 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?

  15. VLBI network with ALMA Science Case for Band 1 Radio Supernovae • 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 100:1 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?

  16. Science Case for Band 1 …and more! • 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.

  17. Science Case for Band 1 ALMA band 1 vs. EVLA Q-band EVLA ALMA Band 1 FIGHT!!!

  18. Science Case for Band 1 ALMA band 1 vs. EVLA Q-band • 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!

  19. Science Case for Band 1 Summary and Final Points • 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!

  20. Science Case for Band 1 james.difrancesco@nrc-cnrc.gc.ca

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