0 Assigned ID: 214 ----- Attempting Submission 1 (Thu Apr 06 12:44:07 GMT 2017) ----- HST Phase I Proposal 214 (m31_stis.apt) successfully submitted. Receipt: # 214-1 ----- Attempting Submission 2 (Thu Apr 06 22:28:18 GMT 2017) ----- HST Phase I Proposal 214 (m31_stis.apt) successfully submitted. Receipt: # 214-4 ----- Attempting Submission 5 (Fri Apr 07 19:52:56 GMT 2017) ----- HST Phase I Proposal 214 (m31_stis.apt) successfully submitted. Receipt: # 214-5 ----- Attempting Submission 6 (Fri Apr 07 20:06:08 GMT 2017) ----- 0 ----- Attempting Submission 1 (Tue Jul 18 21:35:55 GMT 2017) ----- ----- Attempting Submission 2 (Thu Dec 06 18:47:28 GMT 2018) ----- ----- Attempting Submission 3 (Tue Jan 08 05:56:23 GMT 2019) ----- Ultraviolet spectroscopy of the dust extinction in the M31 inner bulge The extinction curve in the central 250 pc region of the M31 bulge is substantially steeper than that in the Milky Way. In addition, there is also clear evidence for a strong 2175 Angstrom extinction bump, the strength of which shows variation among different dusty clumps in the region. To better understand these important characteristics of the extinction properties and their spatial variation, we propose to use the HST/STIS, the only long-slit ultraviolet spectroscopic detector available, to observe two prominent dusty clumps. Combining with the existing photometric data, we will contrast these dusty clumps with neighboring extinction-free regions to construct their extinction curves, which will allow us to precisely measure the slope in the UV wavelength range and to tightly quantify the width and strength of the 2175 Angstrom bump. The results compared with the existing multi-wavelength data will enable us to address such questions as: 1) What causes the steep slope of the extinction curve in the M31 bulge? 2) How does the variation of the extinction curve, especially the 2175 Angstrom bump, depend on the properties and environments of the clumps? The results of this investigation should have strong implications for the dust extinction corrections for stellar light from other similar galactic spheroids. We use the HST/STIS long-slit (52"x2") spectroscopy with the NUV-MAMA camera and G230L grating to observe two dusty clumps in the M31 bulge. From the photometric observations taken by the HST ACS/WFC3 and SWIFT/UVOT camera, Dong et al. 2014, ApJ, 785, 136 found that these two dusty clumps seem to have a steep extinction curve (Rv=2.4-2.5) and strong 2175 A extinction bumps, but with different strengths. Therefore, the main purpose of this program is to use the HST/STIS spectra to characterise the extinction curves of the two dusty clumps, such as Rv and the strength of the 2175 A bump. We use a nearby (~ 1 arcminute away) bright globular cluster, M31GC J004248+411537 (B=16.13, V=15.32 mag) to be the reference target. After the telescope locks the cluster through the acquisition observation, we will shift the telescope to our targets. Limited by the size of the NUV-MAMA camera, the length of the long-slit is accurately 25". Therefore, we use two pointing to cover the two dusty clumps, respectively. In order to make sure that we observe the same lint-of-sight, we use a continuous observations with 5 orbits for each dusty clump. 'STIS-ALONG-SLIT' pattern is used to correct the hot pixels and remove the cosmic rays. Because we extract the spectrum from 100 pixels (0.024608"/pixel in AXIS2), we shift along the grid with 2.46" for three times. Galaxies and the IGM 6 false false true false false false false SUPPORTED ISM BULGE MOLECULAR CLOUD It is a bright globular cluster in the M31 bulge near our targets. (B=16.13, V=15.32 mag) J2000 J2000 ISM MOLECULAR CLOUD ISM MOLECULAR CLOUD STIS/NUV-MAMA Spectroscopic No No G230L 2376 POS-TARG DITHER 2.4608 LINE false true 3 90.0 STIS-ALONG-SLIT 1 false /private/var/folders/56/c_jk44c970v8fj73rtx427cm0006v6/T/OPVisit11562841956904906465.xml The scheduling data was generated by CASM 27.0. CASM was run in Phase II mode. 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CASM was run in Phase II mode. 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