! Proposal 6820, submission 1 ! PI: Alvio Renzini ! Received Fri Feb 16 02:17:46 EST 1996 ! From: rmr@figaro.phys.columbia.edu ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6820,v 6.1 1997/02/05 19:28:46 pepsa Exp $ ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6820,v 6.1 1997/02/05 19:28:46 pepsa Exp $ ! ! Refer to the HST Phase II Proposal Instructions to fill this out ! ! Anything after a "!" is ignored, and may be deleted ! ! All keywords with multiple entries are comma delimited except the ! Visit_Requirements and Special_Requirements keywords which can be ! delimited with carriage returns or semi-colons, but not commas ! ! For help call your Program Coordinator: Bremmer ! Phone: 410-338-4458 , E-mail: bremmer@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Name of Phase I Proposal: archive-1115.renzini.prop ! Date generated: Fri Dec 22 15:47:54 EST 1995 ! Proposal_Information ! Section 4 Title: A Very Deep Luminosity Function for the Galactic Bulge Proposal_Category: GO Scientific_Category: STELLAR POPULATIONS Cycle: 6 Investigators PI_name: Alvio Renzini PI_Institution: ESO CoI_Name: R. Michael Rich CoI_Institution: Columbia University Contact: ! Y or N (designate at most one contact) CoI_Name: Sergio Ortolani CoI_Institution: Universita di Padova Contact: ! Y or N (designate at most one contact) CoI_Name: Laura Greggio CoI_Institution: Universita di Bologna Contact: ! Y or N (designate at most one contact) CoI_Name: Kenneth J. Mighell CoI_Institution: Columbia University Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) We propose to obtain the deepest possible luminosity function in the Galactic bulge. This is the only old, metal rich stellar population that we can study down to M_I~eq +12, unaffected by the dynamical processes that are known to occur in globular clusters. The initial mass function (IMF) of a metal rich stellar population is of fundamental importance in modelling the formation, evolution, and integrated light of galaxies. The discovery of large numbers of microlensing events toward the bulge has greatly increased the need to define the bulge luminosity function to as faint a limit as possible, in order to constrain whether the high microlensing rate can be attributed to normal stars, instead of dark matter or brown dwarfs. Questions ! Free format text (please update) Observing_Description: We will image our bulge field for 5 orbits in both the R and I passband. Our goal is to solidly reach I=27. Care will be taken to do the observations in an optimal fashion (i.e. changing the pointing by a few pixels in between exposures). The WFPC2 exposure time calculator on WWW indicates that for a 13,000s exposure (about what one gets in 5 orbits) we reach I=27 at S/N = 5.1. The faint red end of the main sequence is 1.5 mag fainter in R; at R=28.5 we reach S/N=3.2. Expected color errors of 0.3 mag are large, but we should be able to clearly distinguish the main sequence at the faint end. For A_I=1 mag and (m-M)_0=14.5 (8kpc), then M_I=+12 at I=26.5; this gives us a good chance of reaching 0.1 M\odot, depending on the adopted mass-luminosity relation (e.g. Burrows et al. 1993, ApJ, 406, 158). Extragalactic sources must be carefully considered; we will use color and shape criteria to remove suspicious objects, and also rely on faint galaxy counts (e.g. the Keck counts of Smail et al. 1995 ApJ 449, L105) as a check on possible galaxy contamination. With careful modelling, we should be able to get the last bin of the LF to within a factor of two. The encouraging point is that at I=26, S/N=13.9; errors will be less than the intrinsic width of the bulge main sequence. Given the width of features such as a slope or faint-end downturn, we expect this result to be quite unaffected by such factors as the 0.5 mag depth dispersion of the bulge, or the abundance spread (which is an intrinsic property of the population anyway). Contamination of the sample from the foreground disk main sequence will be addressed using 2 approaches. First, the ridgeline of the bulge main sequence should be well defined, and we will make every effort to purify the sample on the basis of color. But this may be difficult at the faint end. Our second approach is to take advantage of the rapidly growing knowledge of the faint end of the disk luminosity function from other HST observations. (e.g. Bahcall et al. 1994, ApJ 435, L51; Medium Deep Survey team project) and to statistically correct for the presence of the faint foreground main sequence. Note that our solid angle subtends a much larger physical volume (and samples a population of much higher density) in the bulge than it does in the disk, so we do not expect this correction to affect our measurements. Further, since the sight line rapidly drops out of the disk, we are confident that the Solar neighborhood disk lumninosity function will be useful for this correction. We will also reduce archival WFPC2 images of other bulge fields, which can give us additional insight on the bright end of the disk luminosity function. To summarize, we feel that this difficulty can be overcome in a very straightforward way and that its effect can be well quantified. Note that two teams (Westphal and Trauger) have obtained deep 2000s exposures in V and I of two Galactic bulge fields, Baade's Window and Sgr I. These fields are not only more crowded but also suffer more extinction, as they lie closer to the Galactic center than our proposed field. Since the fields are more reddened and they are imaged in V and I, the red colors of the faintest stars will truncate the detected faint end further. Parallel FOC Observations: while not absolutely required for the science, we believe that deep parallel observations should be obtained if it does not adversely affect the primary WFPC2 program. U,B,V exposures with FOC/96 will further constrain the reddening and will provide an alternate measurement of the brighter IMF with a different instrument. Real_Time_Justification: We have obtained the deepest possible ground-based frames of bulge fields at b=-6 and -8 using the ESO NTT. These CCD images are in U, B, V, and I. We will use these to (1) improve the calibration and (2) as input for simulated fields. At b=-6 in 0.4 arcsec seeing, one can reach only 1 mag below the turnoff in the bulge fields. Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number:1 Target_Name:NGC6558-FLD1 Alternate_Names: Description:STELLAR CLUSTER, GLOBULAR CLUSTER Position: RA=18H 11M 05.0S +/- 0.2S, !10 arcmin E DEC=-31D 45' 49.0" +/- 0.5" ! RA=18H 10M 18.40S +/- 0S, center ! DEC=-31D 45' 49.0" +/- 0", ! PLATE-ID=0000 Equinox:2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch:2000 Annual_Parallax: Flux:V=28.0 B-V=2.0 ! faintest end of main sequ. SURF(V)=19.0 E(B-V)=0.3 +/- 0.1 Comments:Galactic Bulge Field ! This is a template for a single visit containing a single exposure ! Repeat exposure and visit blocks as needed Visits ! Section 6 Visit_Number:01 Visit_Requirements:ORIENTation 83D TO 83D ! Section 7.1 Visit_Comments: Exposure_Number:10 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:WFPC2 Opmode:IMAGE Aperture:PC1-FIX Sp_Element:F606W Wavelength: Optional_Parameters:CLOCKS=NO, ATD-GAIN=7 !, CR-SPLIT=0.5 Number_of_Iterations:1 Time_Per_Exposure:2000S Special_Requirements:LOW-SKY ! Section 7.2 Exposure_Number:12 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:FOC/96 Opmode:IMAGE Aperture:512x512 Sp_Element:F342W Wavelength: Optional_Parameters: Number_of_Iterations:1 Time_Per_Exposure:2400S Special_Requirements:PAR WITH 10 ! Section 7.2 Exposure_Number:20 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:WFPC2 Opmode:IMAGE Aperture:PC1-FIX Sp_Element:F814W Wavelength: Optional_Parameters:CLOCKS=NO, ATD-GAIN=7 !, CR-SPLIT=0.5 Number_of_Iterations:1 Time_Per_Exposure:2200S Special_Requirements:LOW-SKY ! Section 7.2 Exposure_Number:22 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:FOC/96 Opmode:IMAGE Aperture:512x512 Sp_Element:F430W Wavelength: Optional_Parameters: Number_of_Iterations:1 Time_Per_Exposure:2500S Special_Requirements:PAR WITH 20 ! Section 7.2 Exposure_Number:30 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:WFPC2 Opmode:IMAGE Aperture:PC1-FIX Sp_Element:F606W Wavelength: Optional_Parameters:CLOCKS=NO, ATD-GAIN=7 !, CR-SPLIT=0.5 Number_of_Iterations:1 Time_Per_Exposure:2200S Special_Requirements:LOW-SKY ! Section 7.2 Exposure_Number:32 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:FOC/96 Opmode:IMAGE Aperture:512x512 Sp_Element:F480LP Wavelength: Optional_Parameters: Number_of_Iterations:1 Time_Per_Exposure:2500S Special_Requirements:PAR WITH 30 ! Section 7.2 Exposure_Number:40 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:WFPC2 Opmode:IMAGE Aperture:PC1-FIX Sp_Element:F814W Wavelength: Optional_Parameters:CLOCKS=NO, ATD-GAIN=7 !, CR-SPLIT=0.5 Number_of_Iterations:1 Time_Per_Exposure:2200S Special_Requirements:LOW-SKY ! Section 7.2 Exposure_Number:42 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:FOC/96 Opmode:IMAGE Aperture:512x512 Sp_Element:F342W Wavelength: Optional_Parameters: Number_of_Iterations:1 Time_Per_Exposure:2500S Special_Requirements:PAR WITH 40 ! Section 7.2 Exposure_Number:50 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:WFPC2 Opmode:IMAGE Aperture:PC1-FIX Sp_Element:F606W Wavelength: Optional_Parameters:CLOCKS=NO, ATD-GAIN=7 !, CR-SPLIT=0.5 Number_of_Iterations:1 Time_Per_Exposure:2200S Special_Requirements:LOW-SKY ! Section 7.2 Exposure_Number:52 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:FOC/96 Opmode:IMAGE Aperture:512x512 Sp_Element:F430W Wavelength: Optional_Parameters: Number_of_Iterations:1 Time_Per_Exposure:2500S Special_Requirements:PAR WITH 50 ! Section 7.2 Exposure_Number:60 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:WFPC2 Opmode:IMAGE Aperture:PC1-FIX Sp_Element:F814W Wavelength: Optional_Parameters:CLOCKS=NO, ATD-GAIN=7 !, CR-SPLIT=0.5 Number_of_Iterations:1 Time_Per_Exposure:2200S Special_Requirements:LOW-SKY ! Section 7.2 Exposure_Number:62 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:FOC/96 Opmode:IMAGE Aperture:512x512 Sp_Element:F480LP Wavelength: Optional_Parameters: Number_of_Iterations:1 Time_Per_Exposure:2500S Special_Requirements:PAR WITH 60 ! Section 7.2 Visits ! Section 6 Visit_Number:02 Visit_Requirements:ORIENTation 83D TO 83D Visit_Comments:All exposures with same orientation, both visits. Second visit due to SAA. Exposure_Number:70 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:WFPC2 Opmode:IMAGE Aperture:PC1-FIX Sp_Element:F814W Wavelength: Optional_Parameters:CLOCKS=NO, ATD-GAIN=7, CR-SPLIT=0.5 Number_of_Iterations:1 Time_Per_Exposure:2000S Special_Requirements:LOW-SKY ! Section 7.2 Exposure_Number:72 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:FOC/96 Opmode:IMAGE Aperture:512x512 Sp_Element:F342W Wavelength: Optional_Parameters: Number_of_Iterations:1 Time_Per_Exposure:2400S Special_Requirements:PAR WITH 70 ! Section 7.2 Exposure_Number:80 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:WFPC2 Opmode:IMAGE Aperture:PC1-FIX Sp_Element:F606W Wavelength: Optional_Parameters:CLOCKS=NO, ATD-GAIN=7, CR-SPLIT=0.5 Number_of_Iterations:1 Time_Per_Exposure:2200S Special_Requirements:LOW-SKY ! Section 7.2 Exposure_Number:82 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:FOC/96 Opmode:IMAGE Aperture:512x512 Sp_Element:F430W Wavelength: Optional_Parameters: Number_of_Iterations:1 Time_Per_Exposure:2500S Special_Requirements:PAR WITH 80 ! Section 7.2 Exposure_Number:90 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:WFPC2 Opmode:IMAGE Aperture:PC1-FIX Sp_Element:F606W Wavelength: Optional_Parameters:CLOCKS=NO, ATD-GAIN=7, CR-SPLIT=0.5 Number_of_Iterations:1 Time_Per_Exposure:2200S Special_Requirements:LOW-SKY ! Section 7.2 Exposure_Number:92 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:FOC/96 Opmode:IMAGE Aperture:512x512 Sp_Element:F480LP Wavelength: Optional_Parameters: Number_of_Iterations:1 Time_Per_Exposure:2500S Special_Requirements:PAR WITH 90 ! Section 7.2 Exposure_Number:100 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:WFPC2 Opmode:IMAGE Aperture:PC1-FIX Sp_Element:F814W Wavelength: Optional_Parameters:CLOCKS=NO, ATD-GAIN=7, CR-SPLIT=0.5 Number_of_Iterations:1 Time_Per_Exposure:2200S Special_Requirements:LOW-SKY ! Section 7.2 Exposure_Number:102 ! Section 6.5 Target_Name:NGC6558-FLD1 Config:FOC/96 Opmode:IMAGE Aperture:512x512 Sp_Element:F480LP Wavelength: Optional_Parameters: Number_of_Iterations:1 Time_Per_Exposure:2500S Special_Requirements:PAR WITH 100 ! Section 7.2 ! Uncomment or copy exposure level special requirements needed ! INTeractive ACQuisition FOR ! ONBOARD ACQuisition FOR ! SAVE OFFSET ! USE OFFSET ! POSition TARGet , ! SAME POSition AS ! DO FOR TARGets ! FGS only ! PARallel WITH ! GROUP-FGS WITHIN