Transcript Document

CADC
JCMT Legacy Surveys,
the JCMT Data Management System,
and Science with Archival Data
(Sub)Millimetre Observing Techniques
Russell O. Redman
JCMT Legacy Surveys
• Legacy Projects with HARP/ACSIS & SCUBA2
– Too big for PATT Proposals
– Too valuable to omit
– Too obvious to award to one small group
• Seven projects authorized
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Debris Disks Survey
Gould's Belt Survey
Spectral Scan Survey
Galactic Plane Survey
Local Universe Survey
Cosmology Survey
SCUBA-2 All Sky Survey (SASSy)
JCMT Legacy Surveys
• Debris Disk Survey
Many main-sequence stars are surrounded by dusty
“debris” disks which are fed by colliding asteroids
and comets orbiting the stars, and thus trace the
extrasolar equivalents of the Kuiper and asteroid belts
in the Solar System. This survey will use SCUBA-2
to search 500 nearby main-sequence stars for submm
radiation from the dust. At submm wavelengths the
stellar photospheric signal is irrelevant, and cold
disks are more easily detected than at shorter IR
wavelengths.
JCMT Legacy Surveys
• Gould’s Belt Survey
We will map with SCUBA-2 almost all star-forming regions within
0.5 kpc that are accessible by the JCMT. Most of these are
associated with Gould’s Belt and include many well-known regions.
Towards the regions surveyed by SCUBA-2, the survey will be
sensitive to every Class 0 & I protostar and every L1544-like prestellar core within 0.5 kpc and will take the number of such known
sources from tens to thousands. We will obtain HARP maps, in
three CO isotopomers, of the thousand brightest sources in order to
distinguish between protostellar and pre-stellar cores, determine
outflow characteristics, and probe the kinematic and density
properties of the sources in a uniform manner. We will also map the
brightest hundred sources with the SCUBA-2 polarimeter,
producing the first statistically significant set of polarization maps
in the submillimetre.
JCMT Legacy Surveys
• Spectral Scan Survey
Stars form in the densest, coldest, most quiescent regions of
molecular clouds. Molecules provide the only probes which
can reveal the dynamics, physics, chemistry and evolution of
these regions. The Spectral Legacy Survey (SLS) proposes to
use the unique spectral imaging capabilities of HARP/ACSIS
to study the molecular inventory and the physical structure of a
sample of objects spanning different evolutionary stages and
different physical environments in molecular clouds and to
probe their evolution during the star formation process. It is
proposed to obtain fully sampled single-footprint spectral scans
complete from 325 GHz to 375 GHz of 3 low mass protostars,
one outflow and 5 young high mass sources, plus scans over 16
GHz of the band towards one PDR and one prestellar core.
JCMT Legacy Surveys
• Galactic Plane Survey
This survey will map two thirds of the Galactic
Plane in the submillimetre continuum with
SCUBA-2. The survey will provide the means to
answer key questions in massive star formation by
examining all stages of the process and all the
significant mechanisms operating on scales from
dense cores to that of the whole Galaxy. The
sample size and vast range of environments will
place massive star formation research onto a firm
statistical basis for the first time. This will allow
the most exhaustive investigation into the physics
that determines the upper IMF that can be
undertaken in a spiral galaxy from our unique
close-up vantage point.
JCMT Legacy Surveys
• Local Universe Survey
We propose a survey with the JCMT using
SCUBA-2 and HARP of a sample of 331
nearby galaxies. With a large, well-selected
sample, we will be able to search for
variations in the physical processes in the
ISM as a function of galaxy type,
metallicity, star formation rate, mass, and
environment. Specific science goals include:
searching for evidence of cold dust and
measuring its mass fraction in galaxies of
different types; measuring the amount of
warm, dense molecular gas associated with
star formation using the CO J=3-2 line; etc.
NGC 2903 (Stevens et al. 2005)
JCMT Legacy Surveys
• Cosmology Survey
The survey will obtain an image as deep as that obtained
for the HDF, but over an area comparable to a sky-survey
Schmidt plate. It will yield a sufficiently robust sample of
sources with redshift information to allow the clustering
strength of submm galaxies to be accurately measured, and
the link between sub-mm galaxies and dark-matter halos to
be established as a function of redshift. It will allow the
detailed study of the high-redshift progenitors of the richest
structures seen in the present-day universe. The proposed
observations will provide enough information to calculate
bolometric luminosities, which in turn will allow us to
refine the ‘Lilly/Madau’ diagram, and establish the link
between obscured and visible star formation over cosmic
history.
JCMT Legacy Surveys
• SCUBA-2 All Sky Survey
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The aims of this survey of the sub-mm sky using the SCUBA-2 are:
– to provide an unbiased volume-limited census of local star formation within 1 kpc;
– to complete the census of massive Infrared Dark Clouds (IRDCs) within our Galaxy;
– to carry out a census of star-formation at high galactic latitude & solve the distributed TTauri problem;
– to identify extreme members of the population of sub-mm galaxies and constrain the
number count models for bright objects;
– to probe foregrounds relevant for Planck but at high angular resolution;
– to leave a lasting legacy for ALMA by completely surveying the sky visible to both JCMT
and ALMA.
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The “All Sky” referred to is a declination band in the range (–30, +70) degrees,
encompassing 18,000 square degrees.
JCMT Legacy Surveys
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Survey membership is still open
– Members must be from partner countries
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– Be prepared to put in some work
• Observing, data reduction, analysis…
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Student thesis projects will be protected
Observations will start
– HARP in 07A
– SCUBA-2 in 07B (?)
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Public pages at http://www.jach.hawaii.edu/JCMT/surveys/
Wiki pages at http://wiki.jach.hawaii.edu/jssg_wiki-bin/wiki/SiteMap
– username survey; password legacy
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See wiki pages for membership
– Survey coordinators
– Data Archive Coordinators (DAC)
JCMT-Archive
• Canadian Astronomy Data Centre
– Maintains JCMT Archive
• Raw data files
• Reduced data
– Various formats
– Primarily to aid selection of raw data
– UNTIL NOW!!!
JCMT-DMS
Data Management System
CADC
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HARP-B/ACSIS & SCUBA2 are mapping instruments
– > 200 TB of raw data!
– Limited storage at JCMT
– Solution: data streams daily from JCMT -> CADC -> Users
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 NEW  Proprietary data will be distributed to users through the CADC
– Every raw data file comes flagged with a release date
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PROPRIETARY before the release date
PUBLIC after the release date
CADC users (i.e. with accounts) will be gathered into groups
Each PATT project & legacy survey constitutes a group
Only group members have access to proprietary data
CADC users can be members of multiple groups (projects)
JCMT-DMS
Access Control
CADC
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JAC set initial group administrators
Five levels of access
– General public
• Public data products & metadata
• Public outreach
– Public users
• + public raw data
• Requires CADC account
– Group members
• + proprietary data & metadata
• Requires group membership
– Group administrator
• + add/remove group members
• Assigned by JAC
– OMP
JCMT-DMS
Data Reduction
• New CADC Services for Data Reduction
– Reduction of raw data to basic data products
– Processing into advanced data products
– Acceptance of externally generated data products
JCMT-DMS
Basic Data Products
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Reduced data
– SCUBA-2
• Stokes I images (jiggle & scan maps)
– Separate images for 850 and 450 m
• Stokes IQU (or QU ?) cubes with polarimeter
– HARP / ACSIS
• Spectral datacubes (jiggle and scan maps)
– Separate datacubes for each sub-band
• Spectra (single points, 2&3 receptor chopping, etc.)
• Spectro-polarimetric hypercubes
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Standard ORAC-DR data reduction
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Sky subtraction
De-spiking
Calibration
Mosaicing
Etc…
Intended to be publication quality!
JCMT-DMS
Product Groupings
• Products produced for different kinds of grouping
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Observation
Night
Project
Public
(chiefly for quality checking)
(if observed > 1 time during night)
(if observed on > 1 night)
(if observed in > 1 project)
• Release date for products = latest release date of raw data
– observation, night, and project products are initially proprietary
– Public products generated after raw data becomes public
• Multiple versions will be generated for project & public products
JCMT–DMS
Advanced Data Products
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Supported Products
– Source & Line Catalogs
• Clump-finding in 2D and 3D
– Spectral Index Maps (SCUBA2)
– Polarization Catalogs
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Advanced products defined by Legacy Survey requirements
– Algorithms still under development
• send advice & suggestions to your survey Data Archive Coordinator (DAC)
– Probably run under ORAC-DR (but does not have to be)
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Does NOT include
– Visualization
– Modeling
– Analysis
CADC
JCMT-DMS
External Products
• Raw data and basic products can also be processed externally
– e.g. cross-correlate SCUBA2 clumps list with other CO maps
– Improved/custom data reduction algorithms
– (Custom reduction by user request at CADC???)
• Check-in of externally generated advanced data products
– Products need to be vetted for format, content and suitability
– Compatibility and standards
• Images and data cubes must have WCS meeting FITS I, II and III
– Spitzer, MSX, etc. (GLON-CAR, GLAT-CAR)
– JCMT-OT (JSky - J2000.0 only; may need conversion routine)
• Check FITS files with fitsverify + + +
• PLEASE - no public announcements until products have been
checked into the CADC and are at least accessible to group members!
JCMT-DMS
Versions
• Versions are required for
– Project products
• Over-written regularly
– Published results
• Saved indefinitely
• There is a journal-sponsored movement to store published data
(not just papers) with permanent URLs
– CADC wants to join this effort
– CADC is willing to create permanent URLs to hold product
descriptions (provenance)
Science with Archives
Proposal Preparation
• Has the source already been observed?
• Have similar sources been observed?
– Brightness, integration times, observing modes…
• Has the source been observed at other transitions
– CO, HCO+, H2CO, …
– Line or continuum
• Has the source been observed at other observatories?
– Simultaneous proposals to multiple telescopes often fail
– Representative sources might already have been observed
Science with Archives
Data Mining
• Large data sets are rarely analyzed completely
– One man’s meat is another man’s poison (and vice versa)
• Time variability
• Moving sources
• Exotic objects?
• Cross-correlation of datasets
– Objects prominent at multiple wavelengths
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Pulsars
Quasars
Star-forming regions
H II regions
Etc…
Science with Archives
Virtual Observatory
• Major, international effort to make available electronically every
public astronomical observation
– Many things to many people
– STANDARDS!!!!
• (Start with FITS and generalize to everything…)
• Octet
– Early example of VO tool
– Finds associations amongst observations
– Launch from http://test.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/cvo/
Science with Archives
Octet
• Associations found using multiple, simultaneous queries
– Associations must overlap in RA, Dec
• Queries built of several conditions
– Usually only one position condition
– Energy/wavelength/frequency condition, not instrument/observatory
QuickTime™ and a
TIFF (LZW) decompressor
Science with Archives
Octet
• Displays association list
– List observations by query
– Select observations for display in Aladin
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Science with Archives
Octet / Aladin
• Image 21cm continuum
• Contours
– Red - 21cm continuum
– Blue - 850 micron continuum
• Items to note
– DR15
• Dust belt (850 m)
– IRDC (850 m)
– Ring from LBV
• Beware of coincidences!
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.