High Redshift Starburst Galaxies

Data reduction and analysis

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Data reduction

The raw FITS files were retrieved from the HST archive and converted to GEIS format (using the strfits task) for further processing with IRAF/STSDAS. The working directory is /data/milan5/max/beckwith/. There was no need to recalibrate the images, because the pipeline-calibrated images were processed with the best reference files. Two images were taken with each filter, so cosmic rays were removed by combining the two images with the crrej task. Some cosmic ray residue remains, which will affect object detection and photometry. The Q1623 (PC1 and WF3) and Q2038 (WF4) fields suffer from some severe saturation and scattered light effects, due to bright stars in the field. Only one of the high priority absorbers (Q2038-012D) is affected by this. Mosaic images were then produced using wmosaic:

Analysis

After plugging the actual ORIENT angles (above) into the Excel spreadsheet, I was able to locate all of the high priority absorber galaxies and most of the lower priority ones. I used the images in Mannucci et al. as a guide, and also compared your coordinates with those measured by SExtractor as another check.

Steve -- you might want to verify my identifications, and/or try to identify the absorbers I haven't been able to (but which should be in the field of view).

To prepare the images for SExtractor, each chip had to be split into it's own FITS file. I masked the chip edges to prevent spurious detections there. The chip edges will eventually have to be properly flagged, rather than masked, otherwise photometry of objects near the edges would be adversely affected.

The strategy is to use the F814W images for object detection, and then to do photometry at those locations in both the F814W and corresponding F450W images (which may or may not have any flux for every object). SExtractor identifies all the high-priority absorbers (and hundreds of others) with a detection sigma=1.5. Once we are done tweaking the SExtractor parameters, I will run it on every chip of every object, and get B-I colors for every object. Will probably also use GIM2D for further parameter extraction.

There are still many detections of hot pixels and cosmic ray residue. I am still working to improve the detection parameters (especially the filter), but we could also simply manually reject spurious detections from our catalog, or manually build up a catalog of absorbers and absorber-candidates.

These are the corresponding SExtractor coordinates for the high priority absorbers I have identified in the images The complete set of catalogs and check images are below. Also see the corresponding thumbnail images: : 


absorber  chip    ID    x pixel    y pixel     RA          DEC
--------  ----   ---    -------    ------- ----------- -----------

Q0100A?   WF2     71    629.218    233.116  15.7724386 +13.2902375

Q0201     WF3    103    717.011    338.065  31.2317161 +36.8215468
Q0201A    WF3     94    654.586    398.225  31.2345154 +36.8206964
Q0201C    WF2    146    738.770    172.120  31.2091606 +36.7964213
Q0201D    WF4    112    615.318    356.562  31.2550830 +36.7998592

Q1623     WF2     91    486.523    392.403 246.4567941 +26.7855569
Q1623A    WF2     72    497.492    482.890 246.4559435 +26.7879615
Q1623A    WF2     79    485.246    454.891 246.4564761 +26.7872626
Q1623B    WF2     76    210.405    479.400 246.4646999 +26.7893288
Q1623E?   WF4     82    527.744    394.334 246.4886834 +26.7706458
Q1623F?   WF4     67    427.855    445.041 246.4859004 +26.7687956
Q1623F?   WF4     89    486.981    348.387 246.4871983 +26.7717086

Q2038B    WF2     70    746.866    533.219 310.1985099  -1.1211316
Q2038C    PC1     87    416.853    352.771 310.2223765  -1.1253023
Q2038D    WF4     61    698.159    353.970 310.2415361  -1.1142128
Q2038D    WF4     62    688.615    353.612 310.2413268  -1.1143739

Q2348     PC1     16    306.498    632.453 357.7410094  -0.8693663
Q2348A    PC1     48    438.915    432.347 357.7388056  -0.8672814
Q2348B    WF3     82    509.272    371.234 357.7221755  -0.8828517

Object catalogs*:

Check images**:

*The catalogs contain only detection coordinates for now, photometry coming soon...

**The check images are all rotated with respect to the mosaic images, such that the occultation regions are always on the left and bottom of the image.

Maintained by Max Mutchler, mutchler@stsci.edu