! $Id: 26,v 4.1 1994/07/26 20:54:39 pepsa Exp $ coverpage: title_1: PAGB STARS IN ELLIPTICAL AND BULGE-DOMINATED NEARBY GALAXIES sci_cat: STELLAR POPULATIONS sci_subcat: OLD FIELD STARS proposal_for: GO pi_title: DR. pi_fname: JOE pi_lname: ASTRONOMER pi_inst: STSCI pi_country: USA pi_phone: (301) 338-4700 keywords_1: PAGB STARS, POPULATION II, ELLIPTICAL GALAXIES, keywords_2: UV IMAGING hours_pri: 7.05 num_pri: 3 foc: Y pi_position: PROF. OF ASTRONOMY ! end of coverpage abstract: line_1: We propose to search for the stellar population which line_2: produces the far ultraviolet rising branch from 1200-1800 A line_3: in the spectral energy distributions of early-type galaxies. line_4: One of the most likely sources of this hot emission are line_5: evolved post-asymptotic giant branch (PAGB) stars. We line_6: estimate that the brightest PAGB stars at the distance of M31 line_7: can be unambiguously detected using the far-UV imaging line_8: capabilities of HST+FOC. The possible presence of other kinds line_9: of hot stellar components that could contribute flux to the line_10: rising branch (e.g. young stars, accreting white dwarf stars line_11: in binaries) can also be detected in these images, as they line_12: will be intrinsically brighter than PAGB stars, but less line_13: numerous. If the source of this far -UV flux is PAGB stars, line_14: their absolute magnitudes in galaxies of different mean line_15: metallicities are critical tests of current theories of line_16: PAGB evolution. ! ! end of abstract general_form_proposers: lname: ASTRONOMER fname: JOE title: DR. inst: SPACE TELESCOPE SCIENCE INSTITUTE country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: We propose to image the central regions of M31, M32 and NGC line_2: 205 by using the FOC in the F/48 configuration. We need to line_3: image each target using the far-UV filter F150W. To avoid line_4: problems related to the disuniformity in the response and line_5: defect in the photocatode, we are requesting that two images line_6: (about one hour each) be obtained for each galaxy, in order line_7: to provide reliable number counts of faint UV-bright stars line_8: (a critical test of the new PAGB models). The F150W filter line_9: isolates the spectral region where PAGB stars are relatively line_10: the brightest, and where the galaxy background is very low. line_11: The bulge of M31 is an object of high metallicity for which line_12: we expect about 200 bright PAGB stars within the F/48 line_13: aperture. Fewer bright PAGB stars are expected in M32 (about line_14: 20), both from the known lower UV flux in that galaxy, and line_15: from the lower metallicity. The fewest PAGB stars are line_16: expected to be found in NGC 205, but blue horizontal branch stars line_17: could be present if there is a wide mix of metallicity in line_18: this galaxy. In addition, the presence of known, ongoing star line_19: formation in NGC 205 could contribute significant numbers of line_20: main sequence, stars even in regions without obvious star line_21: formation. In all cases we expect to detect individual stars line_22: in these galaxies, of which both the luminosities and the line_23: number will be important to this study. ! question: 4 section: 1 line_1: To detect bright PAGB stars (Mv about +1) in external line_2: galaxies it is necessary to operate in the far-UV (both where line_3: they emit their largest flux, and at which they are more line_4: easily discriminated against redder stars) with a large line_5: telescope, since they are faint (mv > 25). High angular line_6: resolution is necessary to isolate crowded objects against a line_7: non negligible background. The observations here proposed line_8: represent a one of the final goals of a long term project line_9: carried out by the proposers both from space (IUE) and from line_10: the ground, as well through theoretical modelling of the late line_11: stages of stellar evolution. ! question: 5 section: 1 line_1: Our estimate of the exposure times with the aberrated HST is line_2: based on the following ingredients: 1. We require a 10% line_3: photometric accuracy (S/N=10) for a PAGB star at the knee of line_4: the slowest of the Schoenberner evolutionary tracks line_5: (M_core=0.546M_o, log L/L_o=2.95, log T_e=4.93, hereafter our line_6: reference PAGB star) and a clear detection (S/N=5) for a PAGB line_7: star which is one magnitude fainter. 2. We concentrate on the line_8: F/48 + F150W combination, which gives the best contrast line_9: between the hot stellar population and the underlying cold line_10: stars. 3. We use the measured FOC PSF in the UV and in line_11: particular the fact that 15% of the PSF flux is contained in line_12: the central 13 pixels (radius of 0.09 arcsec). This core is line_13: the important part of the PSF for the detection and line_14: measurement of faint point sources. 4. We consider the line_15: following components of the background: the detector line_16: background as measured in orbit (0.0019 cnt/s/pix), the sky line_17: background, which is dominated by the diffuse galactic light line_18: as given in Fig. 42 of the FOC Instrument Handbook, and the line_19: contribution due to unresolved sources and to the wings of line_20: the PSF of the resolved sources. In order to estimate this line_21: third background component we take all the flux measured by line_22: Burstein et al. (1988, Ap.J. 328, 440) in the large IUE line_23: aperture and we assume it is distributed with a radial ! question: 5 section: 2 line_1: profile like the B-band one given by Kent (1987, A.J. 94, line_2: 306) for M32. In a 2 hour exposure with the F150W filter, line_3: subdivided into two single exposures slightly shifted by 1 line_4: arcsec, we foresee a S/N varying between 8 at the nucleus and line_5: 14 at the edge of the field for our reference PAGB star, line_6: while S/N will be 5 at 2 arcsec from the nucleus and 7 at line_7: the edge for a PAGB one magnitude fainter. ! question: 6 section: 1 line_1: Justification for any special calibrations, use of dark line_2: time, or uninterupted exposures goes here. ! question: 7 section: 1 line_1: We plan to use the data from the pipeline calibration (RSDP) line_2: at STScI. ! question: 8 section: 1 line_1: Any additional comments go here. ! question: 9 section: 1 line_1: A description of any previous HST data goes here. ! question: 10 section: 1 line_1: Resources provided by your home institution goes here. ! !end of general form text general_form_address: lname: ASTRONOMER fname: JOE title: DR. category: PI inst: STSCI addr_1: 3700 SAN MARTIN DRIVE city: BALTIMORE state: MD zip: 21218 country: USA phone: (301) 338-4700 ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: NGC221-UV-STARS name_2: M32 descr_1: B,131 pos_1: PLATE-ID = 01JV, pos_2: RA = 0H 42M 41.71S +/- 0.05S, pos_3: DEC = +40D 51' 54.1" +/- 0.5" equinox: 2000 rv_or_z: V = -217 comment_1: FLUXVAL_2 IS FOR THE REFERENCE comment_2: PAGB STAR AT 4" FROM THE NUCLEUS. fluxnum_1: 1 fluxval_1: V=18.7+/-0.5, TYPE=O5 V, E(B-V)=0.08 fluxnum_2: 2 fluxval_2: F(1500)=11+/-4E-18 ! targnum: 2 name_1: NGC224-UV-STARS name_2: M31 descr_1: B,131 pos_1: PLATE-ID = 01JV, pos_2: RA = 0H 42M 44.9S +/- 0.1S, pos_3: DEC = +41D 16' 08" +/- 1" equinox: 2000 rv_or_z: V = -299 comment_1: FLUXVAL_2 IS FOR THE REFERENCE comment_2: PAGB STAR AT 4" FROM THE NUCLEUS. fluxnum_1: 1 fluxval_1: V=18.7+/-0.5, TYPE=O5 V, E(B-V)=0.08 fluxnum_2: 2 fluxval_2: F(1500)=11+/-4E-18 ! targnum: 3 name_1: NGC205-UV-STARS-POS1 descr_1: B,131 pos_1: PLATE-ID = 01JV, pos_2: RA = 0H 40M 22.57S +/- 0.05S, pos_3: DEC = +41D 41' 1.4" +/- 0.5" equinox: 2000 rv_or_z: V = -239 comment_1: FLUXVAL_2 IS FOR THE REFERENCE comment_2: PAGB STAR AT 4" FROM THE NUCLEUS. fluxnum_1: 1 fluxval_1: V=18.7+/-0.5, TYPE=O5 V, E(B-V)=0.03 fluxnum_2: 2 fluxval_2: F(1500)=11+/-4E-18 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.000 targname: NGC221-UV-STARS config: FOC/48 opmode: IMAGE aperture: 512X512 sp_element: F150W,F130LP num_exp: 1 time_per_exp: 70.5M s_to_n: 10 fluxnum_1: 2 priority: 1 req_1: GUIDE TOL 0.010" / 1-6; req_2: CYCLE 1 / 1-6 ! linenum: 2.000 targname: NGC221-UV-STARS config: FOC/48 opmode: IMAGE aperture: 512X512 sp_element: F150W,F130LP num_exp: 1 time_per_exp: 70.5M s_to_n: 10 fluxnum_1: 2 priority: 1 req_1: POS TARG 0.0,1.0; req_2: SAME ORIENT FOR 2 AS 1 ! linenum: 3.000 targname: NGC224-UV-STARS config: FOC/48 opmode: IMAGE aperture: 512X512 sp_element: F150W,F130LP num_exp: 1 time_per_exp: 70.5M s_to_n: 10 fluxnum_1: 2 priority: 2 ! linenum: 4.000 targname: NGC224-UV-STARS config: FOC/48 opmode: IMAGE aperture: 512X512 sp_element: F150W,F130LP num_exp: 1 time_per_exp: 70.5M s_to_n: 10 fluxnum_1: 2 priority: 2 req_1: POS TARG 0.0,1.0; req_2: SAME ORIENT FOR 4 AS 3 ! linenum: 5.000 targname: NGC205-UV-STARS-POS1 config: FOC/48 opmode: IMAGE aperture: 512X512 sp_element: F150W,F130LP num_exp: 1 time_per_exp: 70.5M s_to_n: 10 fluxnum_1: 2 priority: 3 ! linenum: 6.000 targname: NGC205-UV-STARS-POS1 config: FOC/48 opmode: IMAGE aperture: 512X512 sp_element: F150W,F130LP num_exp: 1 time_per_exp: 70.5M s_to_n: 10 fluxnum_1: 2 priority: 3 req_1: POS TARG 0.0,1.0; req_2: SAME ORIENT FOR 6 AS 5 ! ! end of exposure logsheet ! No scan data records found