Assigned ID: 459 ----- Attempting Submission 1 (Fri Feb 25 18:03:12 GMT 2011) ----- HST Phase I Proposal 459 (m101_uv_bump.apt) successfully submitted. ----- Attempting Submission 2 (Fri Feb 25 23:36:44 GMT 2011) ----- The only warnings about a lack of target acquistions for our observations. Target acquistions are not needed as our goal is to measure the total spectrum of each region within a 10" diameter. ----- Attempting Submission 1 (Thu Jul 07 17:15:51 GMT 2011) ----- HST Phase II Proposal 12556 (12556.apt) successfully submitted. ----- Attempting Submission 2 (Thu Jul 07 23:55:17 GMT 2011) ----- HST Phase II Proposal 12556 (12556.apt) successfully submitted. ----- Attempting Submission 3 (Fri Jul 08 14:29:00 GMT 2011) ----- The only warnings about a lack of target acquistions for our observations. Target acquistions are not needed as our goal is to measure the total spectrum of each region within a 10" diameter. Investigating the Enigmatic Ultraviolet 2175 A Extinction Feature and Correlation with Infrared Aromatic/PAH emission in M101 The 2175 Angstrom ultraviolet dust extinction feature has been known for more than 45 years, but the source of the extinction has yet to be positively identified. One of the leading contenders in dust grain models is small aromatic/PAHs grains. Through IR observations of HII regions in the spiral galaxy M101, PAHs have measured emission strengths that dramatically weaken at large radii and ionizations. The parameter space of these HII regions in terms of metallicity, ionization, and PAH emission strengths is the largest of any known galaxy. To explore the connection between the 2175 A extinction feature and IR aromatic/PAH emission strengths, we propose to observe the six regions in M101 (5 HII and the nucleus) using near-UV and far-UV gratings (G230L/G140L) with the MAMA detectors on STIS. The STIS instrument provides the opportunity to obtain high S/N UV spectra integrated over the same large spatial scales of the previous IR observations (~78 square arcsec) in minimal time (2 orbits per region). From the measured spectra, we will employ stellar evolutionary synthesis and radiative transfer models to extract the intrinsic strength of the 2175 A extinction feature. The 2175 A features strengths will be compared with the published emission strengths of five different aromatic/PAH features in all six regions. If the 2175 A feature is associated with aromatic/PAHs grains, we will see a strong correlation. The lack of a strong correlation will imply the need for significant modification of leading dust models.
We are planning on observing six regions in M101 (5 HII regions and the nucleus) with the MAMA far-UV G140L and near-UV G230L gratings of STIS. Both the far-UV and near-UV data are required because of the broadness of the 2175 A feature, and the strength of the 2175 A bump is known to anti-correlate with the strength of the far-UV rise. To meet the objectives of this proposal, we require the 52"X2" slit. Two of the HII regions (nucleus and Hodge 602) are observable using the same slit but require the orientation of the slit to be 95-100 degrees east of north. For the 52"x2" STIS aperture, this requires the ORIENT parameter to be between 140.35-145.35 degrees or 320-325 degrees. The remaining HII regions do not require a specific slit orientation. To cover the same full 10" diameter of each HII region as observed in the IR, a total of five minimal slews of 1.8" each is required in the dispersion direction for a total of six observations per grating. The slightly smaller than 2" slews (1.8") for 6 slit positions is to ensure that the full 10" region is covered with some margin for pointing uncertainties (no target aquisition). Our goal is to achieve at least a S/N of 50 at 1400 A and 2175 A in the far-UV and near-UV, respectively. This is the S/N required to get a 5-sigma detection of the weakest 2175 AA extinction feature seen in the previous HST FOS sample (i.e., Searle 5) at the flux level of our faintest target (nucleus). The near-UV and far-UV HII region fluxes are from archival M101 GALEX data of the Nearby Galaxies Survey. The fluxes are measured in 10" diameter apertures and converted to surface brightnesses. We estimate the gain in S/N we will achieve using STIS by summing up the 400 pixels in the spatial direction, binning the pixels in wavelength space (we only require a R = 10 to resolve the 2175 A feature), and summing up over the five exposures. The final S/N is ~50 when these calculations are done. The minimium input S/N per resolution element using the online STIS exposure time calculator is 0.16 for the G230L near-UV grating, and 0.12 for the G140L far-UV grating. The calculations done for far-UV are identical to near-UV, and we assume a final R = 10 for both. As an exception, we do not require a S/N of 50 for Hodge 602, which is significantly fainter than the other HII regions in our sample. The spectra of Hodge 602 is acquired at the same time as the nucleus and we require the final S/N of the nucleus to be 50. The final S/N of Hodge 602 will be ~20. Both the nucleus and Hodge 602 are at the center of M101 and share similar parameter spaces in PAH strengths, ionizations, and metallicities. We will be able to detect a moderately strong 2175 A extinction feature in Hodge 602. Target acquistions are not needed as we are targeting large extended regions (10" diameter) and our sources are not point sources. An error of 1" in the center of the STIS maps will comprimise the comparision of the STIS versus Spitzer fluxes. ISM IN EXTERNAL GALAXIES 12 false 0.0 0.0 false false false false SUPPORTED ISM HII REGION J2000 J2000 Fluxes (ergs/s*cm^2*A*arcsec^2) for circular apertures of 10" diameter: GALEX near-uv=5.76e-17, GALEX far-uv=8.60e-17 ISM HII REGION J2000 J2000 Fluxes (ergs/s*cm^2*A*arcsec^2) for circular apertures of 10" diameter: GALEX near-uv=1.19e-16, GALEX far-uv=2.36e-17 ISM HII REGION J2000 J2000 Fluxes (ergs/s*cm^2*A*arcsec^2) for circular apertures of 10" diameter: GALEX near-uv=1.11e-16, GALEX far-uv=2.76e-16 ISM HII REGION J2000 J2000 Fluxes (ergs/s*cm^2*A*arcsec^2) for circular apertures of 10" diameter: GALEX near-uv=6.66e-17, GALEX far-uv=1.69e-16 ISM HII REGION J2000 J2000 Fluxes (ergs/s*cm^2*A*arcsec^2) for circular apertures of 10" diameter: GALEX near-uv=2.12e-16, GALEX far-uv=4.07e-16 STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/FUV-MAMA Spectroscopic No No G140L 1425 POS-TARG MOSAIC DITHER 1.8 STIS-ALONG-SLIT false true 6 0.0 POS-TARG STIS-PERP-TO-SLIT 90.0 1 false POS-TARG MOSAIC DITHER 2 1.8 STIS-ALONG-SLIT true true 20 6 0.0 POS-TARG STIS-PERP-TO-SLIT 90.0 3 true /home/kgordon/Papers/Proposals/HST/c19/M101_UV/phaseII/OP-cache/12556-v01.xml The scheduling data was generated by CASM 19.3. CASM was run in Phase II mode. No target acq. needed given that the observation is to measure the total spectrum in a 10" diameter region. Small errors in the centering (within ~1") are ok. 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The final S/N will be the sum along the slit as well as a coadd of all 5 positions. All the ETC runs in the progam are for a single slit. The final S/N will be the sum along the slit as well as a coadd of all 5 positions. /home/kgordon/Papers/Proposals/HST/c19/M101_UV/phaseII/OP-cache/12556-v02.xml The scheduling data was generated by CASM 19.3. CASM was run in Phase II mode. No target acq. needed given that the observation is to measure the total spectrum in a 10" diameter region. Small errors in the centering (within ~1") are ok. 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CASM was run in Phase II mode. No target acq. needed given that the observation is to measure the total spectrum in a 10" diameter region. Small errors in the centering (within ~1") are ok. 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CASM was run in Phase II mode. No target acq. needed given that the observation is to measure the total spectrum in a 10" diameter region. Small errors in the centering (within ~1") are ok. 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