Submillimeter ( < 1 mm) Continuum Imaging at CSO: a Retrospective

C. Darren Dowell (Caltech),on behalf of all students, postdocs, and staff inspired and supported by Tom to build an instrument and then wait for low water vapor

symposium honoring T. G. Phillips, Pasadena, CA, February 2009

Acknowledgments/BibliographyContact the author at:

cdd@submm.caltech.edu

I thank the following people for supplying photos for this poster:

Dominic BenfordEd BufilSunil GolwalaJohn Vaillancourt

< 1 mm Continuum Detectors at CSO Case Study: The Galactic Center

Sagittarius A region

Sagittarius B2 region

SHARC II Photo Gallery

Correlated Photon Noise in SHARC II ArraySince the SHARC II detectors are closely spaced (0.6 /D), and the photon mode occupation number is high, adjacent detectors show correlated noise, as can be seen in these normalized detector-detector covariances:

CSO bolometer: Lis, Carlstrom, & Keene, 1991, ApJSHARC I: N. Wang et al., 1996, ApOptSHARC II: Dowell et al., 2003, SPIE, 4855Hertz: Schleuning et al., 1997, PASP Dowell et al., 1998, ApJMKIDcam: Glenn et al., 2008, SPIE, 7020

To Chop or Not To ChopThe single-bolometer instrument and SHARC Isuccessfully used:• chopping mirror,• NOD2 image reconstruction.A known disadvantage of chopping with only oneamplitude and direction is the poor sensitivity to spatialfrequencies which are multiples of the chop, and ringingaround bright sources.

For most observing, SHARC II does not use thechopper, but instead uses crossing scans:• Lissajous patterns,• “billiards” patterns.To overcome 1/f noise from the sky and instrument, Isometimes set zero-signal reference regions in the map,kind of like chopping/nodding in all directions.

1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

single bolometer350,800 m

SHARC I350,450 m

Hertz350 m pol.

SHARC II350,450 m

MKIDcam750,850 m

Lis & Carlstrom (1994, ApJ) Dowell et al. (1999, ASP Conf. Ser.)

Serabyn et al. (1997, ApJL): detection of Sgr A* at 350 m with SHARC I

Bally et al. (2009, in prep.)

Chuss et al. (2003, ApJ): magnetic fields mapped with Hertz (and also KAO), superposed on radio image

Yusef-Zadeh et al. (2006,2008,2009, ApJ): detection of Sgr A* variability at 350,450,850 m with SHARC II

Bally et al. (2009, in prep.)Dowell et al. (1999, ASP Conf. Ser.)Lis & Carlstrom (1994, ApJ)

core in Orion (Li et al. 2007, ApJ)

Moon at 850 m (high-pass filtered on right)

submm galaxies at z = 0.8-3.4(Kovacs et al. 2006, ApJ)

CSO 350 m beam(mapped using Mars)

Fomalhaut, Vega, Eri debris disks at 350 m(Marsh et al. 2005, 2006; Backman et al. 2009; ApJ)

A851 cluster survey, 5 mJy rms(Marshall, Dowell, et al., in prep.)

elliptical galaxy NGC 807(Leeuw et al. 2006, ApJ)

disturbed galaxy NGC 3627(Murphy, in prep.)

blank field survey(Khan et al. 2007, ApJ)

grayscale shows: d1d2 / sqrt(d12 d2

2)

pixels separated by one row

(9% correlation)

pixels separated by one column

(9% correlation)

chopped dual-beam response in sky plane (left) and fourier plane (right)

(Emerson, Klein, & Haslam 1979, A&A)