0 Assigned ID: 2530 ----- Attempting Submission 1 (Sun Sep 14 00:44:50 GMT 2014) ----- 0 ----- Attempting Submission 1 (Tue Sep 30 19:21:06 GMT 2014) ----- We propose a 100ksec Chandra observation of NGC7457. The primary goal of this observation is to test for variations in the initial mass function (IMF). Many recent studies have proposed that the IMF varies systematically as a function of early-type galaxy mass. This has potentially dramatic consequences and must to be confirmed. The number of LMXBs in a galaxy (per stellar luminosity) can be used to provide an independent test of this hypothesis (see Peacock et al. 2014). Unfortunately, only galaxies with intermediate to high masses currently have the data needed to perform this test. The proposed observation of the elliptical galaxy NGC7457 will detect an order of magnitude more LMXBs in a low mass galaxy - hence providing the crucial constraint needed to significantly test for a variable IMF. As part of this proposal, we require two HST orbits to obtain high spatial resolution photometry that covers the D_25 ellipse of this galaxy. This will enable us to identify optical counterparts to the X-ray sources detected and thereby classify them in to field LMXBs, globular cluster LMXBs and background AGN. We will observe 2 ACS/WFC fields along the major axis of NGC7457. Each field will be observed for 1 orbit - producing a small 1*2 mosaic. Due to the high ellipticity of the galaxy, we require that the observations are taken at an angle of 52.5 degrees. This will align the images with the major axis of the galaxy, allowing us to cover its entire D_25 ellipse. A range of 50-55 degrees acceptable, as is a 180 degree rotation (230-235). Both fields will be observed with the ACS-WFC-DITHER-LINE dither pattern, with two points and the default separation. This will cover the chip gap and can be used to remove cosmic rays and hot pixels (we therefore set CR-SPLIT=0). Both fields will be observed through the F475W and F850LP filters with total exposure times of: F475W = 1100s (2*550s) F850LP = 1050s (2*525s) The ACS/WFC ETC predicts that these exposure times will give 3 sigma detection limits of F475W(AB)=27.6 and F850LP(AB)=25.9. This will be sufficient to achieve our scientific objective of identifying the optical counterparts to X-ray sources in these fields. UNRESOLVED STELLAR POPULATIONS AND GALAXY STRUCTURE Default false false false false false SUPPORTED GALAXY LENTICULAR This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 ACS/WFC Imaging No No F475W ACS/WFC Imaging No No F850LP POS-TARG DITHER 3.011 LINE false false 2 85.28 ACS-WFC-DITHER-LINE 1 false 1412105630137 /private/var/folders/ny/y2rfgxpn4k37g754z2ph3gd00001bc/T/OPVisit3627625131617325037.xml The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13942 :visit-id "01" :proposal-version -1 :trans-version "20140605" :date "30-Sep-2014 15:33:49.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13942 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13942 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2923 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) true 1 0 1412105631423 /private/var/folders/ny/y2rfgxpn4k37g754z2ph3gd00001bc/T/OPVisit6865029130431267252.xml The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13942 :visit-id "02" :proposal-version -1 :trans-version "20140605" :date "30-Sep-2014 15:33:51.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13942 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13942 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2923 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) true 1 0