13942( 3) - 07-Oct-2014 18:10:45 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13942 Version: 3 Check-in Time: 07-Oct-2014 18:10:45 STScI Edit Number: 1 Title Does the IMF vary with galaxy mass? The X-ray binary population of a key galaxy, NGC7457 ------------------------------------------------------------------------------------ Type Cycle GO 22 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Mark B. Peacock Michigan State University Y CoI: Prof. Stephen E. Zepf Michigan State University N CoI: Dr. Thomas J. Maccarone Texas Tech University N CoI: Dr. Arunav Kundu Eureka Scientific Inc. N CoI: Prof. Anthony H. Gonzalez University of Florida N CoI: Dr. Bret Lehmer The Johns Hopkins University N CoI: Prof. Claudia Maraston University of Portsmouth N ------------------------------------------------------------------------------------ Abstract 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. ------------------------------------------------------------------------------------ Observations Description ------------------------ 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) 13942( 3) - 07-Oct-2014 18:10:45 - [ 2] 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. ------------------------------------------------------------------------------------ 13942( 3) - 07-Oct-2014 18:10:45 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC7457 GALAXY, LENTICULAR RA=23H00M59.9340S, J2000 V = 11.87 DEC=+30D08'41.61" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 13942( 3) - 07-Oct-2014 18:10:45 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 3.011 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 85.28 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 13942( 3) - 07-Oct-2014 18:10:45 - [ 5] Visit: 01 Visit Requirements: ORIENT 50D TO 55 D; ORIENT 230D TO 235 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC7457 ACS/WFC ACCUM WFCENTER F475W CR-SPLIT=NO 1 551 S POS TARG (1102 S) -91.90090701096506, -6.426337441993791; PATTERN 1 1-2 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC7457 ACS/WFC ACCUM WFCENTER F850LP CR-SPLIT=NO 1 525 S POS TARG (1050 S) -91.90090701096506, -6.426337441993791 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ NGC7457 1 ACS/WFC ACCUM WFCENTER F475W 1 none none none 1 N/A NGC7457 1 ACS/WFC ACCUM WFCENTER F475W 2 none none none 1 N/A NGC7457 2 ACS/WFC ACCUM WFCENTER F850LP 1 none none none 1 N/A NGC7457 2 ACS/WFC ACCUM WFCENTER F850LP 2 none none none 1 N/A 13942( 3) - 07-Oct-2014 18:10:45 - [ 6] Visit: 02 Visit Requirements: SAME ORIENT AS 01 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC7457 ACS/WFC ACCUM WFCENTER F475W CR-SPLIT=NO 1 551 S POS TARG (1102 S) 91.90090701096506, 6.426337441993791; PATTERN 1 1-2 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC7457 ACS/WFC ACCUM WFCENTER F850LP CR-SPLIT=NO 1 525 S POS TARG (1050 S) 91.90090701096506, 6.426337441993791 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ NGC7457 1 ACS/WFC ACCUM WFCENTER F475W 1 none none none 1 N/A NGC7457 1 ACS/WFC ACCUM WFCENTER F475W 2 none none none 1 N/A NGC7457 2 ACS/WFC ACCUM WFCENTER F850LP 1 none none none 1 N/A NGC7457 2 ACS/WFC ACCUM WFCENTER F850LP 2 none none none 1 N/A 13942( 3) - 07-Oct-2014 18:10:45 - [ 7] Summary Form for Proposal 13942 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFCENTER ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 230D TO 235 D, ORIENT 50D TO 55 D, PATTERN 1 1-2, POS TARG -91.90090701096506, -6.426337441993791, POS TARG 91.90090701096506, 6.426337441993791, SAME ORIENT AS 01 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F475W, F850LP ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC7457 ------------------------------------------------------------------------------------------------------------------------------------