12523( 6) - 25-Jan-2013 12:13:55 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12523 Version: 6 Check-in Time: 25-Jan-2013 12:13:55 STScI Edit Number: 2 Title Dissecting the integrated light of a massive elliptical galaxy with pixel-to-pixel fluctuations: is the IMF bottom-heavy? ------------------------------------------------------------------------------------ Type Cycle GO 19 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Charlie Conroy University of California - Santa Cruz Y CoI: Prof. Pieter van Dokkum Yale University N ------------------------------------------------------------------------------------ Abstract The stellar initial mass function (IMF) is a critical ingredient in the interpretation of extragalactic observations and provides important clues to the physics of star formation. Unfortunately, the low-mass IMF (M<0.3 Msun) is very difficult to measure beyond the Galaxy because low mass dwarf stars contribute only a few percent to the integrated light of old stellar populations. Using high quality Keck spectra we recently found that massive elliptical galaxies in the Virgo and Coma clusters have enhanced dwarf-sensitive absorption features, indicating a very "bottom-heavy" IMF with many more low-mass stars than the IMF in our Galaxy. The main uncertainty in this result is that the subtle absorption features that we ascribe to dwarf stars may actually be due to unusual abundance patterns in giant stars. Here we propose to directly determine whether three key IMF sensitive spectral features in massive elliptical galaxies are caused by giants or by dwarfs. We will exploit the high angular resolution of ACS, in combination with its unique ramp filters, to measure pixel-to-pixel fluctuations in the light of these spectral features for one of the massive Virgo elliptical galaxies that we previously observed with Keck (NGC 4649). Pixel-to-pixel fluctuations are caused by Poisson variations in the number of giants, and by correlating the behavior of a spectral feature with the number of giants in each pixel we directly measure whether that feature comes from giants or dwarfs. ------------------------------------------------------------------------------------ Observations Description ------------------------ We are observing a single target, the elliptical galaxy M60, in 6 ramp filters and in the broad F814W filter. The aim is that the "on" and "off" exposures for a given feature (Na I, CaT, FeH) fall approximately on the same area of the detector. The four bluest settings will fall on the WFC-1 chip; the two reddest settings (FeH "on" and FeH "off") will fall on the WFC-2 chip. In order to have broad band data for all of the filters, we split the F814W observations in two visits: one for the WFC1 ramp aperture and one for the WFC2 ramp aperture. A standard dither pattern of 4 exposures is used to improve the sampling and identify hot pixels. The data can be taken at any ORIENT but it is crucial that all 8 visits are taken at the same ORIENT. 12523( 6) - 25-Jan-2013 12:13:55 - [ 2] Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 12523( 6) - 25-Jan-2013 12:13:55 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 3 M-49 GALAXY, ELLIPTICAL RA=12H29M46.7980S, J2000 V = 12.17 DEC=+08D00'1.48" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 12523( 6) - 25-Jan-2013 12:13:55 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.265 Line_Spacing 0.187 Coordinate_Frame POS-TARG Pattern_Orient 20.67 Angle_Between_Sides 69.05 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 12523( 6) - 25-Jan-2013 12:13:55 - [ 5] Visit: 01 Visit Requirements: 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M-49 ACS/WFC ACCUM WFC1-IRAM FR853N 8230 1 1000 S GS ACQ SCENARIO BASE1B3; P see below PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8230 1 none none none 1 1267.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8230 2 none none none 1 1255.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8230 3 none none none 2 1363.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8230 4 none none none 2 1352.0 S MP 12523( 6) - 25-Jan-2013 12:13:55 - [ 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M-49 ACS/WFC ACCUM WFC1-IRAM FR853N 8365 1 1000 S GS ACQ SCENARIO BASE1B3; P see below PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8365 1 none none none 1 1267.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8365 2 none none none 1 1255.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8365 3 none none none 2 1363.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8365 4 none none none 2 1352.0 S MP 12523( 6) - 25-Jan-2013 12:13:55 - [ 7] Visit: 03 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M-49 ACS/WFC ACCUM WFC1-IRAM FR853N 8560 1 500 S GS ACQ SCENARIO BASE1B3; P see below PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8560 1 none none none 1 554.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8560 2 none none none 1 554.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8560 3 none none none 1 554.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8560 4 none none none 1 544.0 S MP 12523( 6) - 25-Jan-2013 12:13:55 - [ 8] Visit: 04 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M-49 ACS/WFC ACCUM WFC1-IRAM FR853N 8800 1 500 S GS ACQ SCENARIO BASE1B3; P see below PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8800 1 none none none 1 554.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8800 2 none none none 1 554.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8800 3 none none none 1 554.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA FR853N 8800 4 none none none 1 544.0 S MP 12523( 6) - 25-Jan-2013 12:13:55 - [ 9] Visit: 05 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M-49 ACS/WFC ACCUM WFC2-ORAM FR1016N 9960 1 1000 S GS ACQ SCENARIO BASE1B3; P see below PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 M-49 ACS/WFC ACCUM WFC2-ORAM FR1016N 9960 1 500 S PATTERN 1 2 P see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ M-49 1 ACS/WFC ACCUM WFC2-ORA FR1016N 9960 1 none none none 1 1267.0 S MP M-49 1 ACS/WFC ACCUM WFC2-ORA FR1016N 9960 2 none none none 1 1255.0 S MP M-49 1 ACS/WFC ACCUM WFC2-ORA FR1016N 9960 3 none none none 2 1363.0 S MP M-49 1 ACS/WFC ACCUM WFC2-ORA FR1016N 9960 4 none none none 2 1352.0 S MP M-49 2 ACS/WFC ACCUM WFC2-ORA FR1016N 9960 1 none none none 3 602.0 S MP M-49 2 ACS/WFC ACCUM WFC2-ORA FR1016N 9960 2 none none none 3 602.0 S MP M-49 2 ACS/WFC ACCUM WFC2-ORA FR1016N 9960 3 none none none 3 602.0 S MP M-49 2 ACS/WFC ACCUM WFC2-ORA FR1016N 9960 4 none none none 3 593.0 S MP 12523( 6) - 25-Jan-2013 12:13:55 - [ 10] Visit: 06 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M-49 ACS/WFC ACCUM WFC2-ORAM FR1016N 9810 1 1000 S GS ACQ SCENARIO BASE1B3; P see below PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ M-49 1 ACS/WFC ACCUM WFC2-ORA FR1016N 9810 1 none none none 1 1267.0 S MP M-49 1 ACS/WFC ACCUM WFC2-ORA FR1016N 9810 2 none none none 1 1255.0 S MP M-49 1 ACS/WFC ACCUM WFC2-ORA FR1016N 9810 3 none none none 2 1363.0 S MP M-49 1 ACS/WFC ACCUM WFC2-ORA FR1016N 9810 4 none none none 2 1352.0 S MP 12523( 6) - 25-Jan-2013 12:13:55 - [ 11] Visit: 07 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M-49 ACS/WFC ACCUM WFC1-IRAM F814W 1 1000 S GS ACQ SCENARIO BASE1B3; P see below PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ M-49 1 ACS/WFC ACCUM WFC1-IRA F814W 1 none none none 1 1267.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA F814W 2 none none none 1 1255.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA F814W 3 none none none 2 1363.0 S MP M-49 1 ACS/WFC ACCUM WFC1-IRA F814W 4 none none none 2 1352.0 S MP 12523( 6) - 25-Jan-2013 12:13:55 - [ 12] Visit: 08 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M-49 ACS/WFC ACCUM WFC2-ORAM F814W 1 1000 S GS ACQ SCENARIO BASE1B3; P see below PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ M-49 1 ACS/WFC ACCUM WFC2-ORA F814W 1 none none none 1 1267.0 S MP M-49 1 ACS/WFC ACCUM WFC2-ORA F814W 2 none none none 1 1255.0 S MP M-49 1 ACS/WFC ACCUM WFC2-ORA F814W 3 none none none 2 1363.0 S MP M-49 1 ACS/WFC ACCUM WFC2-ORA F814W 4 none none none 2 1352.0 S MP 12523( 6) - 25-Jan-2013 12:13:55 - [ 13] Summary Form for Proposal 12523 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC1-IRAMP, WFC2-ORAMP ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GS ACQ SCENARIO BASE1B3, PATTERN 1 1, PATTERN 1 2, SAME ORIENT AS 01 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W, FR1016N, FR853N ------------------------------------------------------------------------------------------------------------------------------------ Target Names M-49 ------------------------------------------------------------------------------------------------------------------------------------