Submillimeter Data for SINGS

George J. Bendo & Robert D. Joseph

(A ''George's Adventures in Learning OpenOffice'' Presentation)

Outline

● Overview of JCMT and SCUBA

● Basic data processing

● Current archival data

● Future observations

James Clerck Maxwell Telescope

● 15 m submillimeter telescope

● Located on Mauna Kea (elevation 4,090 m)

● Began operating in 1987

● Operated by Joint Astronomy Center

● UK controls most observing time; Canada, Netherlands, Hawaii also get shares

● Instruments include bolometer array (SCUBA) and heterodyne receivers

More Views of the JCMT

SCUBA (Submillimeter Common-User Bolometer Array)

● Two sets of bolometers that can observe the same field simultaneously

– 91 element short wavelength (450 m) array

– 37 element long wavelength (850 m) array● 3 longer wavelength (1.1, 1.35, 2.0 mm) bolometers flank the long

wavelength array but are rarely used

● Arrays can be used in three basic observing modes

– Stare photometry

– Jiggle map

– Scan map

SCUBA bolometer arrays

SCUBA Processing Software

Because the data comes in terms of bolometer signal measurements over time, special software is needed to process the data into intensity maps .

The JAC has created the SURF package, which works with other Starlink packages and data in the NDF (N-dimensional Data File) format.

Basic SCUBA Processing(Steps for all observing modes)

● reduce_switch Split data into individual bolometer signals

● flatfield Flatfields the data

● extinction Corrects the data for atmospheric extinction; also splits the data into short and long wavelength components

● change_quality Remove ''bad'' bolometers (i.e. bolometers producing noisy data)

● despike2, scuclip Remove data spikes

Example of JCMT Data before Rebinning

Jiggle Map / Stare PhotometryData Processing

● remsky Remove background as well as systematic variations across image from sky noise

● rebin Combines multiple data files and rebins the data in RA and declination

Scan Map Data Processing

● scan_rlb Remove variations in offset from bolometer to bolometer

● calcsky, remsky Remove background as well as systematic variations across image from sky

noise

● rebin Rebins the data in RA and declination for each individual scan

● remdbm Combines all individual scans into a final image

Calibration

● Planets (especially Uranus and Mars) favored

● Secondary calibrators (mostly planetary nebulae) also used

● JCMT documentation treats source calibration as though sources are similar to point sources but these instructions will be disregarded when calibrating SINGS data

● Calibrator counts will be measured in 2' aperture to create calibration factor to apply to maps after processing

Final Maps

● Images will be in fits format

● Data will be calibrated in Jy

● Beam sizes are approximately ~8” at 450m and ~15” at 850m

● Image scales will be 1” / pixel (but scale can be adjusted)

● Image artifacts may be present

– Hexagonal image edges

– Hot pixels (particularly around edges of pointings

– Holes in images (where bolometers masked out)

– Grainy sky-noise

– Large scale background fluctuations in scan maps

Examples of SCUBA PSFs

SINGS data in SCUBA archive

24 SINGS galaxies found in SCUBA archives

– 8 galaxies are non-detections

– 8 galaxies are detections but contain no significant signal outside the nucleus

– 8 galaxies contain detections of extended structure (although these structures are sometimes small)

Non-Detection (Jiggle Map of NGC 855)

Non-Detection (Scan Map of NGC 628)

Central Detection (Jiggle Map of NGC 2798)

Central Detection (Scan Map of NGC 4579)

Extended Source Detection (Jiggle Map of NGC 4826)

Extended Source Detection (Jiggle Map of NGC 7552)

Extended Source Detection (Jiggle Map of NGC 7331)

Extended Source Detection (Jiggle Map of NGC 4631)

Planned JCMT Observations

● Proposed observations through R. D. Joseph at University of Hawaii

● 9 shifts awarded as part of flexible observing

– Proposal ranked 8 out of 16

– Requested conditions for observing 850 m (450 m possible but unlikely)

– 5 shifts given high priority (observations likely)

– 4 shifts given low priority (observations made only if weather is good)

● Estimate that at least 12 - 13 galaxies can be observed

● Data will consist of jiggle maps covering central 2.6' x 2.3'

Future Submillimeter Observations

● JCMT

– Most sensitive telescope at both 450 & 850 m

– Best at resolving and mapping moderately extended objects

– Multiple wavelength observations possible

– Difficult to apply directly; must apply through collaborators at institutions with access to telescope (but we will probably have future access through Hawaii)

Future Submillimeter Observations (continued)

● HHST (Heinrich Hertz Submillimeter Telescope)

– Scan mapping capabilities at 850 m (but mapping mode is inefficient)

– Easily accessible to Steward Observatory staff

– Lower sensitivity (~5x)● CSO (Caltech Submillimeter Observatory)

– Scan and stare mapping modes at 350, 450, & 850 m

– Easily accessible to Caltech staff

– Optomized for 350 m, which is exceedingly difficult; longer wavelength observations inferior to JCMT

Timeline

Jan 2003 Finish processing archival data; check archives for new data

Feb - Jul 2003Observe targets with JCMT

Mar 2003 Submit JCMT proposal for additional targets

Sep 2003 Finish processing new JCMT data; submit JCMT proposal for additional targets