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Documentation

Find information, examples, FAQs and extensive descriptions of the data, curated by the survey teams.

Docs ref

Reference

A complete guide to using Data Central
Feb. 1, 2018 by L. Mannering
Feb. 9, 2018, 5:38 p.m. L. Mannering

Cutout Service

A multi-band image cutout routine for all imaging data (GAMA PDR) hosted at Data Central. Generate single band or rgb images, overplot contours, customize plotting options and download pngs/fits for multiple sources/positions.

Syntax

Position

Source List source_list

Enter a source name or list of names (separated by a comma). Source names must be prepended by the survey_datarelease prefix. Sources are addressed in the form:

SURVEY_DATARELEASE_SOURCENAME

with an underscore (_) as the delimiter.

For example, GAMA source 202627 as catalogued in the second data release is addressed as: 

gama_dr2_202627 

not any of the following

G202627  g202627  202627

The cutout uses the following catalogues to look up identifiers for a particular survey_datarelease.

Survey + Data Release Prefix Table
GAMA DR2 gama_dr2 gama_dr2.InputCatA
SAMI DR1 sami_dr1 sami_dr1.InputCat
GALAH DR1 galah_dr1 galah_dr1.InputCatalog

An example source list might look like:

gama_dr2_202627, sami_dr1_278855

Note: if you submit an ID without the data release prefix (e.g., gama_65406), the cutout will use the most-recent input catalogue as provided by the team (ie., the most recent data release) to try and find the source position.

RA/Dec ra, dec

The cutout supports wide variety of input formats for coordinates:

  • degrees (10.2345d)
  • sexagesimal degrees (1:2:30.43d)
  • sexagesimal hours (1 2 0 hours)
  • degree, arcmin, and arcsec (1d2m3.4s)
  • hour, minute, second (-1h2m3s)

Don't forget to include the string format identifier, e.g., for coordinates in degrees, append 'd'. See astropy's angle documentation for a list of all possible formats.

Upload file upload_file

Upload a file containing one [survey_datarelease_sourcename] or two [RA, Dec] columns (comma separated), as per the format in the RA/Dec fields. You cannot mix source names and positions, upload either a one-column or two-column file.

Accepted file formats: .ascii, .txt, .text (MIME type text/plain). Max file length: 2000 rows. Lines beginning with '#' are ignored. Duplicate entries are ignored.

An example file containing source names might look like:

    # source ids (including survey_dr prefix)
    gama_dr2_202627
    gama_dr2_202628
    gama_dr2_673010
    gama_dr2_202647
    sami_dr1_278855
    gama_dr2_797782
    gama_dr2_202691
    gama_dr2_2026000
        

Similarly, a file containing Ra, Dec:

    # RA, Dec
    12:28:8.96234693960d, -11:14:15.35367885116d

Radius radius (arcseconds)

The radius to cutout. Note that the service will cut out a square region, so radius here is equivalent to half the box width. Maximum value 600".

Greyscale Images

Greyscale greyscale

Select the greyscale checkbox to generate single-band cutouts.

Bands bands

Choose bands from the multiple selection box. To select multiple bands, hold down cmd ⌘ or ctrl and click. The available bands are listed below, though coverage may not be complete across all GAMA regions.

Available Bands
GAMA PDR
Facility Bands
Chandra

0520 0570 2070

GALEX

FUV NUV

HST

F606W F814W F125W F160W F435W F475W F475X F775W F850LP F098M F225W F275W F336W

SDSS

u g r i z

VSTKIDS

u g r i

Subaru

B V g r i z

CFHT

u g r i z H K

VIKING

Z Y J H K

UltraVISTA

Y J H K

WISE

1 2 3 4

Spitzer

I1 I2 I3 I4 M24 M24d M70 M160

Herschel

P70 P100 P160 S250 S350 S500

Region Coverage (for reference only)
GAMA PDR
Region Available Bands
G09, G12, G15

GALEX (FUV,NUV)
SDSS (ugriz)
VIKING (ZYJHK)
WISE (w1,w2,w3,w4)
PACS (70,160)
SPIRE (250,350,500)

G23

GALEX (FUV,NUV)
VIKING (ZYJHK)
PACS (70,160)
SPIRE (250,350,500)

Three colour images

RGB rgb

Select the rgb checkbox to generate a three-band RGB composite image from single-band cutout images. The scaling is taken from the input_scaling field (default = log)

Red rgb_red

Band to use for the red channel.

Green rgb_green

Band to use for the green channel. 

Blue rgb_blue

Band to use for the blue channel.

Image Scaling

For visualization purposes only, the cutout data values are re-mapped. Firstly, values are are normalized to the range (0, 1) and bad values are rejected. The resultant array can be mapped using the input_scaling field. If input_scaling is 'atan' or 'asinh', the user can also supply a stretch_scale, which controls what parts of the data is in the linear or logarithmic regime of the stretch procedure. If set to 'auto' it uses 1/median(abs(data)) to find a useful scale. Lastly, if provided, data are clipped between the locut and hicut values default. This can help enhance features in the data that are otherwise difficult to see.

Input Scaling input_scaling

Linear, logarithmic, atan, asinh and sqrt scalings are supported. 

Stretch Scale stretch_scale

A number to multiply the data by before applying the scaling (affects only asinh and atanh scaling).

Locut locut

Lower clipping quantile (default 0.4) 

Hicut hicut

Upper clipping quantile (default 0.995)

Plot Options

Axis Style axis_style

Choose 'basic' = x/y axes drawn or 'none' = no axes drawn.

Colour Map cmap

Choose a colourmap to represent the cutout data values.

Matplotlib color maps reference

 

Invert Colour invert_color

If possible, invert the selected colour map.

Contour Band contour_band

Overlay the contoured data of a specified band. The choices are given above in the single band section.

Contour Levels contour_levels

Specify the contour levels to overlay (separated by a comma). Contour levels are calculated in terms of standard deviations above the median of pixels in a clipped cutout. The current cutout pixels are clipped at 1.5*standard deviations above and below the median, and contour levels are assigned at X times standard deviations above the median of the remaining pixels. Required if contour_band is given.

Plot Title plot_title

Include an automatically-generated plot title displaying source name and band(s).

Central cutout position plot_center_position

Overplot the central cutout position (symbol: +).

Coordinate grid plot_grid

Overplot the coordinate grid.

Source positions plot_source_positions

Overplot source positions from selected survey_datareleases.

Survey Data Release Marker
GAMA DR2
SAMI DR1
GALAH DR1

Survey source identifiers plot_source_ids

If plot_source_positions has a value, also plot the source ids.

Plot Legend plot_legend

If checked, and plot source positions has a value, overplot the legend identifying the source position in the upper-right corner of the plot window.

Additional Options

Fits fits

If checked, generate .fits files from the cutout regions for download.

Add to the queue run_async

Checking the Add to the queue checkbox above will submit your request to the queue. Typically, quick-look requests (several sources and bands) should be run instantly, but for complicated requests we recommend sending it to the queue!

Submit (unchecked) The request will run immediately, but if it contains many components (sources, contours, lots of bands selected), it could take some time, and you will not be able to close this window whilst it processes.

Queue (checked) Add this request to the queue. Data Central will process your request in the background, and you will receive an email when it completes.

 

Cutout history

If you are logged in to Data Central, your cutout history will be saved. You can revisit your history at any time by clicking on the Cutout History tab.

 

Coming soon

Overplot AAT fiber positions, GAMA apertures, multiple RGBs, colour picker for contour band.

Feb. 1, 2018 by L. Mannering
Feb. 9, 2018, 5:38 p.m. L. Mannering