An Ionizing Photon Rate Map of NGC 6946

0 Assigned ID: 465 ----- Attempting Submission 1 (Fri Apr 10 13:45:48 GMT 2015) ----- HST Phase I Proposal 465 (ngc6946file.apt) successfully submitted. Receipt: # 465-1 PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE PATTERN POSITION OUTSIDE APERTURE Be very careful mixing POS TARG and Center_Pattern = Yes Be very careful mixing POS TARG and Center_Pattern = Yes Be very careful mixing POS TARG and Center_Pattern = Yes Be very careful mixing POS TARG and Center_Pattern = Yes Be very careful mixing POS TARG and Center_Pattern = Yes Be very careful mixing POS TARG and Center_Pattern = Yes Be very careful mixing POS TARG and Center_Pattern = Yes Be very careful mixing POS TARG and Center_Pattern = Yes Be very careful mixing POS TARG and Center_Pattern = Yes 9 point mosaic designed to be observed in a single block with arbitrary orientation - the offsets are handled via POS TARG offsets in the exposures. 110W (the broad band off) and 128N (Paschen beta) are interleaved. Revisions to dither pattern and order of observations following consultation with contact scientist S. Baggett. 1899997995 ----- Attempting Submission 1 (Thu Jul 23 16:15:28 GMT 2015) ----- ----- Attempting Submission 2 (Thu Nov 05 16:42:01 GMT 2015) ----- The postiion offsets are designed to execute a mosaic pointing pattern - I copied them from the offsets (in POS_TARG) generated by the mosaic tool. They overlap by 10% and are a 3x3 spacing. An Ionizing Photon Rate Map of NGC 6946 Significant progress in our understanding of star formation and galaxy evolution depends on ability to obtain precise measurements of the star formation rate on scales from individual regions to large samples of galaxies. In order to do so we need to benchmark star formation rate estimators available for large samples and over wide areas (e.g., Halpha+IR, UV+IR) against high quality, spatially resolved "ground-truth" measurements. This has been done in groundbreaking studies for indivdiual regions, but has yet to be done carefully using maps covering whole area of nearby galaxies. The Paschen beta line is ideal for this purpose: it tracks star formation by tracing ionizing photons the can be cleanly associated with young stars and it is 3x less affected by extinction than the commonly used Halpha line. Most important WFC3 has the demonstrate ability to map Paschen beta at high resolution and excellent sensitivity over the whole area of nearby galaxies. We propose to use this capability to map the active area of active star formation in NGC6946, making only the second deeply sensitive map of Paschen beta across a whole nearby star-forming galaxy. We will use this to (1) inter-compare proposed ground-truth tracers (free-free, optical Balmer decrement, Paschen beta + Halpha) and (2) to improve the calibration of empirical star formation rate estimators by measuring them for individual regions, across large parts of galaxies, and comparing galaxies. Only HST can provide this new and important measurement of an extinction robust tracer of ionizing photon rates at high sensitivity and resolution across a whole galaxy. We aim for a 3 x 3 mosaic in the 128N (Paschen Beta) and 110W (broad band off) filters. The orientation is allowed to be anything as long as it is fixed - that is, we are happy with a circle being our guaranteed coverage and then the square can be pointed any direction around this. UNRESOLVED STAR FORMATION 12 false false false false SUPPORTED GALAXY DISK SPIRAL YES This object was generated by the targetselector and retrieved from the NED database. This is the central position in the galaxy. The flux is the total V (Johnson) magnitude from NED. J2000 J2000 WFC3/IR Imaging No No F128N WFC3/IR Imaging No No F110W POS-TARG DITHER DITHER 4 5.183 WFC3-IR-DITHER-BOX-MIN false 74.653 false 0.365 0.572 2 41.859 POS-TARG WFC3-IR-DITHER-BLOB 18.528 1

false

POS-TARG DITHER DITHER 2 5.183 WFC3-IR-DITHER-LINE false true 0.636 2 41.859 POS-TARG WFC3-IR-DITHER-BLOB 41.788 2

true

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