The Incidence of Highly-Obscured Star-Forming Regions in SINGS Galaxies

Using the new capabilities of the Spitzer Space Telescope and extensive multiwavelength data from the Spitzer Infrared Nearby Galaxies Survey (SINGS), it is now possible to study the infrared properties of star formation in nearby galaxies down to scales equivalent to large HII regions. We are therefore able to determine what fraction of large, infrared-selected star-forming regions in normal galaxies are highly obscured and address how much of the star formation we miss by relying solely on the optical portion of the spectrum. Employing a new empirical method for deriving attenuations of infrared-selected star-forming regions we investigate the statistics of obscured star formation on 500pc scales in a sample of 38 nearby galaxies. We find that the median attenuation is 1.4 magnitudes in H-alpha and that there is no evidence for a substantial sub-population of uniformly highly-obscured star-forming regions. The regions in the highly-obscured tail of the attenuation distribution (A_H-alpha > 3) make up only ~4% of the sample of nearly 1800 regions, though very embedded infrared sources on the much smaller scales and lower luminosities of compact and ultracompact HII regions are almost certainly present in greater numbers. The highly-obscured cases in our sample are generally the bright, central regions of galaxies with high overall attenuation but are not otherwise remarkable. We also find that a majority of the galaxies show decreasing radial trends in H-alpha attenuation. The small fraction of highly-obscured regions seen in this sample of normal, star-forming galaxies suggests that on 500pc scales the timescale for significant dispersal or break up of nearby, optically-thick dust clouds is short relative to the lifetime of a typical star-forming region.Comment: Accepted for publication in ApJ; emulateapj style, 30 pages, 18 figures (compressed versions), 3 table

spacetelescope/drizzlepac: Drizzlepac v3.6.2 release candidate 1

<h2>High-level Summary</h2> <p>Follow on to Release Candidate 0.</p> <h2>What's Changed</h2> <ul> <li>Update code to update WPFC2 chip gaps by @stsci-hack in https://github.com/spacetelescope/drizzlepac/pull/1551</li> <li>HlA-1059: Reference catalog weights corrected by @s-goldman in https://github.com/spacetelescope/drizzlepac/pull/1616</li> <li>HLA-1052: Updated WFPC2 drizzle parameters for HAP by @s-goldman in https://github.com/spacetelescope/drizzlepac/pull/1617</li> <li>Fixed bug in calculation of the measurements for each detected source by @mdlpstsci in https://github.com/spacetelescope/drizzlepac/pull/1614</li> <li>HLA-1048: Redesign of readthedocs documentation by @s-goldman in https://github.com/spacetelescope/drizzlepac/pull/1620</li> <li>Drizzlepac: Ensure the "best" WCS solution is found when using a set by @mdlpstsci in https://github.com/spacetelescope/drizzlepac/pull/1638</li> <li>Correctly fix the wcs preferential order REL > IMG, GAIA*3 > GAIA[2|1] by @mdlpstsci in https://github.com/spacetelescope/drizzlepac/pull/1645</li> <li>drop support for Python 3.8 by @zacharyburnett in https://github.com/spacetelescope/drizzlepac/pull/1541</li> <li>Removed version restriction on Matplotlib by @mdlpstsci in https://github.com/spacetelescope/drizzlepac/pull/1649</li> <li>Allow group specifications as integers or tuples by @mcara in https://github.com/spacetelescope/drizzlepac/pull/1612</li> </ul> <p><strong>Full Changelog</strong>: https://github.com/spacetelescope/drizzlepac/compare/3.6.1...3.6.2rc1</p&gt

spacetelescope/drizzlepac: Drizzlepac v3.6.2 release candidate 2

<h2>High-level Summary</h2> <p>Follow on to Release Candidate 0.</p> <h2>What's Changed</h2> <ul> <li>Pin Astrocut to avoid urllib3 version conflict by @mdlpstsci in https://github.com/spacetelescop/drizzlepac/pull/1689</li> </ul&gt

spacetelescope/drizzlepac: Drizzlepac v3.6.2 release candidate 3

<h2>High-level Summary</h2> <p>Follow on to Release Candidate 0, 1, and 2.</p> <h2>What's Changed</h2> <ul> <li>HLA-1150: MVM failure due to HAPProduct constructor mismatch by @s-goldman in https://github.com/spacetelescope/drizzlepac/pull/1693</li> </ul&gt

ejeschke/ginga: Ginga v2.6.6

Fix for broken sorting in Contents plugin in gtk backends Fix for resize bug in switching in and out of grid view in gtk backends Updated to have efficient support for gtk3 please install compatible pycairo from github.com/pygobject/pycairo if you get a "Not implemented yet" exception bubbling up from a method called cairo.ImageSurface.create_for_data() Addition of a "Quick Mode" to the Pick plugin--see documentation More consistent font handing between widgets and Ginga canvases Bug fix for importing some types of matplotlib color maps Add antialiasing for Qt back end Bug fixes and enhancements for Qt gestures holding shift with pinch now keeps position under cursor New Jupyter notebooks back end based on ipywidgets requirements: "pip install ipyevents" see examples/jupyter-notebook/Jupyter Widget Ideas.ipynb Fixes to various reference viewer plugin