Cannot find file /Users/dokkum/RUNS/Prop/hst_cyc27/cos/prop/vandokkum_cos.pdf 0 Assigned ID: 996 ----- Attempting Submission 1 (Fri Apr 05 23:52:07 GMT 2019) ----- COS FUV PSA science exposures with extended targets have special calibration limitations. See "Errors and Warnings" for more details. COS FUV PSA science exposures with extended targets have special calibration limitations. See "Errors and Warnings" for more details. INEFFICIENT ORDERING OF FP-POS POSITIONS COS FUV PSA science exposures with extended targets have special calibration limitations. See "Errors and Warnings" for more details. COS FUV PSA science exposures with extended targets have special calibration limitations. See "Errors and Warnings" for more details. COS FUV PSA science exposures with extended targets have special calibration limitations. See "Errors and Warnings" for more details. COS FUV PSA science exposures with extended targets have special calibration limitations. See "Errors and Warnings" for more details. INEFFICIENT ORDERING OF FP-POS POSITIONS COS FUV PSA science exposures with extended targets have special calibration limitations. See "Errors and Warnings" for more details. COS FUV PSA science exposures with extended targets have special calibration limitations. See "Errors and Warnings" for more details. I have added a direct image to each of the visits, to verify that the target is in the aperture after the blind offset. This change was approved by the TTRB. I think everything is OK. There is one thing I am slightly concerned about, and that is the pointing move that shows up in the Orbit Planner after the direct image. There should be only one pointing move, after the acquistion of the star, to slew to the target. However, the software also indicates a pointing change in between the direct image and the first spectrum, even though the aperture (PSA) and target are unchanged. I suppose this is normal (e.g. because a spectral element slightly changes things) but I wanted to flag it just in case. -632679301 ----- Attempting Submission 1 (Mon Jul 29 08:08:52 GMT 2019) ----- HST Phase II Proposal 15852 (phase2_15852.apt) successfully submitted. Receipt: # 15852-1 ----- Attempting Submission 2 (Tue Aug 20 19:44:40 GMT 2019) ----- HST Phase II Proposal 15852 (phase2_15852.apt) successfully submitted. Receipt: # 15852-2 ----- Attempting Submission 3 (Tue Aug 20 19:58:12 GMT 2019) ----- HST Phase II Proposal 15852 (phase2_15852.apt) successfully submitted. Receipt: # 15852-3 ----- Attempting Submission 4 (Thu Sep 05 21:44:58 GMT 2019) ----- We are aware of the limitations in the wavelength calibration; an exact calibration is not needed for our program. Testing IMF variation in elliptical galaxies using chromospheric activity of M dwarfs The question whether the stellar initial mass function (IMF) is universal is still unresolved. Perhaps the most persistent claims for IMF variation have come from studies of the centers of elliptical galaxies: several lines of evidence suggest that the IMF is bottom-heavy in those regions compared to the IMF of the Milky Way. Here we propose to test this by searching for the far UV emission lines associated with chromospheric activity on the surfaces of stars. By observing two galaxies with very similar properties but different claimed IMFs we will do a differential experiment: we expect to see UV lines in NGC1407, which has been claimed to have an excess of M dwarfs of a factor of 10, but not in the control galaxy NGC2695. An analysis of the H+K line region of the two galaxies is consistent with this hypothesis but not conclusive. This proposal has risk: the strengths of UV features in M dwarfs in elliptical galaxies have never been measured, and we may detect nothing in both galaxies. However, a detection of the UV lines could provide very strong evidence for IMF variation (if the lines are seen in NGC1407 but not in NGC2695) or against it (if the lines are equally strong in both galaxies). The goal of the program is to search for UV emission lines in two early-type galaxies: NGC1407 and NGC2695. The program is split into 4 visits of 2 orbits each: visit 1: NGC1407 orbit 1: acquisition on offset star + blind offset + direct image on target + G130M exposure at 1291 Ang at FP-POS 3 orbit 2: G130M exposure at 1291 Ang at FP-POS 4 visit 2: NGC1407 orbit 1: acquisition on offset star + blind offset + direct image on target + G160M exposure at 1533 Ang at FP-POS 1-4 (4 splits) orbit 2: G160M exposure at 1533 Ang at FP-POS 1-4 (4 splits) visit 3: like visit 1, but for NGC 2695 visit 4: like visit 2, but for NGC 2695 Brightness of the galaxies --------------------- The program aims to measure faint UV lines, but for the direct imaging and also for the expected continuum emission in the spectra it is important to have an approximate estimate of the magnitudes. These were determined from GALEX FUV and NUV data. The total AB magnitude in the central 2.5'' diameter aperture is AB~21.1 for NGC1407 and AB~21.9 for NGC2695. The FUV-NUV color is ~0 for both galaxies (i.e. the spectrum is roughly flat in Fnu). The average brightness per square arcsec, which is needed in the ETC, is 22.8 for NGC1407 and 23.6 for NGC2695. We are not near bright source limits (even if it is assumed that the galaxies are point sources within the 2.5'' aperture). Brightness of the lines ------------------ These were estimated to be ~1e-15; this is discussed in the Phase 1 proposal. We are not near bright limits. Acquisition --------- Offset stars are used for both targets, as they are too faint for a direct acquisition. The magnitudes of the stars were measured from GALEX NUV images; the AB magnitudes at 2300 Angstrom are 20.46 for the NGC1407 star and 17.16 for the NGC2695 star. For NGC1407 MIRRORA is used. For NGC2695 the star is too bright for MIRRORA, and MIRRORB is used. Exposure times were determined with the ETC, using a S/N=50 criterion. This gave exposure times of ~1.5 minutes for both. The coordinates of the offset stars were obtained from Gaia DR2 and are extremely accurate. The offsets to the galaxies were determined from DECALS imaging and, as a cross-check, 2MASS imaging. They are accurate to ~0.2''. Direct images on target ------------------- After slewing to the science targets a short (300s) imaging exposure will be obtained to verify the location of the galaxy. As we do not know the exact brightness distribution of the galaxies on sub-arcsec scales it is difficult to estimate what, exactly, the S/N ratio will be. We assume that the AB magnitude within a 0.4'' radius aperture is about ~22.5 mag. In 300s this gives a S/N ratio within this aperture of 20, sufficient to determine whether it is properly centered (and whether it is there!). If the light is more spread out, the S/N ratio will be lower, and if it is more peaked, the S/N ratio will be higher, but in either case we should be able to see both galaxies quite clearly if we are in the right place. Following section 6.1 in the Instrument Handbook, FLASH=YES was selected to track the drift of the OSMs. This additional 300s image in each visit was approved by the TTRB. Wavelength settings ---------------- We use only a single setting for G130M (1291) and a single setting for G160M (1533). With these settings all important UV lines are away from gaps. If we added a wavelength setting to cover the gaps one or more lines would get half the exposure time, and we would not gain anything from the added wavelength coverage (as there are no lines in the gaps). FP-POS settings ------------- In the context of COS2025 we can only use FP-POS 3 and FP-POS 4 with the G130M/1291 setting. I simply used position 3 for the first exposure, and position 4 for the second. If there is any reason to do finer splits (that is, subexposures within each exposure, going back and forth between 3 and 4) then we can do that. However, it does not seem anything would be gained, and it would lead to some added overhead. With the G160M/1533 setting we can use all FP-POS settings, and we do. Each exposure is split into 4 subexposures with all 4 settings. The PI and co-I are both experienced users of HST, and experts on the IMF. The key papers that were the motivation for this proposal were written by the two co-Is. Although neither of us has used COS, van Dokkum has extensive experience with the ACS and WFC3 grisms on HST. Stellar Populations Galaxies and the IGM 6 false false true false false false false SUPPORTED STAR UNDESIGNATED NO This is the position of the offset star. Position from Gaia DR2 database. The offset from this star to NGC1407 is 65.6 arcsec West, and 2.7 arcsec South. J2000 J2000 20.46 (GALEX NUV) GALAXY ELLIPTICAL YES This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 STAR UNDESIGNATED NO This is the position of the offset star. Position from Gaia DR2 database. The offset from this star to NGC2695 is 24.0 arcsec West, and 0.4 arcsec North. J2000 J2000 17.16 (GALEX NUV) GALAXY ELLIPTICAL YES The target is 24.0 arcsec West and 0.4 arcsec North of NGC-2695-STAR J2000 COS/FUV Spectroscopic No No G130M 1300 COS/FUV Spectroscopic No No G160M 1600 COS/FUV Spectroscopic No No G130M 1300 COS/FUV Spectroscopic No No G160M 1600 /private/var/folders/nd/frlb74jn1z53gqkzq40hptrm0000gr/T/OPVisit6492837587382601394.xml The scheduling data was generated by CASM 27.2. CASM was run in Phase II mode. 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CASM was run in Phase II mode. 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