! +====================+ ! | PED OUTPUT PRODUCT | ! +====================+ ! ! /yon/data1/nkede/proposals/6105.prop ! Generated by PREPROCESSOR, version 7.0.1e ! Date: Mon Mar 03 12:44:41 EST 1997 Proposal_Information Title: Primary distance measurement to the Virgo Cluster Proposal_Category: GO Scientific_Category: Galaxies & Clusters Cycle: 5 Investigators PI_Name: William E. Harris PI_Institution: Department of Physics and Astronomy, McMaster University CoI_Name: Patrick R. Durrell CoI_Institution: Department of Physics and Astronomy, McMaster University Contact: N CoI_Name: Michael J. Pierce CoI_Institution: Department of Astronomy, Indiana University Contact: N CoI_Name: Jeff Secker CoI_Institution: Department of Physics and Astronomy, McMaster University Contact: N Abstract: The I-band luminosity of the brightest red giant stars in old, metal-poor, halo populations, M_I(tip), is a primary standard candle accurate to +/-0.1 mag, and offers several distinct advantages over other Population II distance indicators. A critical feature of M_I(tip) is that the metallicity of the galaxy's underlying halo population must be less than Fe/H ~ -0.7 dex. However, giant elliptical galaxies like those at the core of the Virgo Cluster possess a metal-rich stellar halo; as a result, any M_I(tip) distance to the Virgo core which is based upon these giant galaxies will suffer an intrinsic bias towards larger distance if compared to local, metal-poor calibrators. We will use WFPC2 in I to resolve the brightest RGB stars in two metal-poor nucleated dwarf ellipticals near M87 (the cD galaxy at the center of the main Virgo Cluster core). Because of its high intrinsic precision, reliance on basic stellar physics, and independence from the current collection of secondary distance estimators, the resulting M_I(tip) Virgo distance will be the most nearly definitive to date, providing a stepping stone to more remote clusters and (eventually) H_0. Questions Observing_Description: We will use WFPC2 with the F814W (``wide I'') filter, which will maximize throughput while preserving a well defined photometric bandpass. The absolute magnitude of the metal- poor RGB tip is at M_I = -4.0 +/- 0.1. If (m-M)(Virgo) = 31.0, we expect the brightest red giants to resolve at I=27.0, corresponding to V=29.0. We will center the PC1 CCD field at a nominal radius from the center of the dE,N galaxy which is equivalent to a V surface brightness of ~26.8 mag per sq arcsec, which simulations show will yield several hundred resolved RGB stars across the frame with no severe crowding problems. We will carry out the CCD photometry with DAOPHOT III (ALLFRAME), by far the best code for crowded field photometry. A sophisticated maximum-likelihood code has been developed to fit a model luminosity function to the data, simultaneously incorporating photometric incompleteness, photometric error, and background contamination: This will be used to fit the steep upturn in the LF at the giant branch tip and to deduce the tip magnitude. Real_Time_Justification: Calibration_Justification: Additional_Comments: Fixed_Targets Target_Number: 1 Target_Name: VCC1104 Alternate_Names: Description: GALAXY, DWARF ELLIPTICAL Position: RA=12H 28M 31.4S +/- 2",DEC=12D 49' 38" +/- 2",PLATE-ID=00IY Equinox: J2000 RV_or_Z: V = +1704 RA_PM: Dec_PM: Epoch: Annual_Parallax: Flux: V = 29.0 B-V = 1.6 Comments: TARGET V MAGNITUDE CORRESPONDS TO BRIGHTEST RED GIANTS IN GALAXY Target_Number: 2 Target_Name: VCC1407 Alternate_Names: Description: GALAXY,DWARF ELLIPTICAL Position: RA=12H 32M 4.33S +/- 2",DEC=11D 52' 45" +/- 2",PLATE-ID=00IY Equinox: J2000 RV_or_Z: V = +941 RA_PM: Dec_PM: Epoch: Annual_Parallax: Flux: V = 29.0 B-V = 1.6 Comments: TARGET V MAGNITUDE CORRESPONDS TO BRIGHTEST RED GIANTS IN GALAXY Solar_System_Targets Generic_Targets Scan_Data Visits Visit_Number: 01 Visit_Requirements: ORIENT 105D TO 105D On_Hold_Comments: Visit_Comments: ORIENT 45D TO 105D NUCLEUS OF GALAXY SHOULD FALL WITHIN WF3. Exposure_Number: 12 Target_Name: VCC1104 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 2400 S Special_Requirements: END ORBIT EXPAND Comments: EXPOSURES 12-17 ARE A 6 STEP SEQUENCE AROUND A HEXAGONAL PATTERN WITH 2.5 PX STEPS Exposure_Number: 13 Target_Name: VCC1104 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 2600 S Special_Requirements: POS TARG 0.115,0.115 END ORBIT EXPAND Comments: Exposure_Number: 14 Target_Name: VCC1104 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 2600 S Special_Requirements: POS TARG 0.115,0.230 END ORBIT EXPAND Comments: Exposure_Number: 15 Target_Name: VCC1104 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 2600 S Special_Requirements: POS TARG 0.0,0.345 END ORBIT EXPAND Comments: Exposure_Number: 16 Target_Name: VCC1104 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 2600 S Special_Requirements: POS TARG -0.115,0.230 END ORBIT EXPAND Comments: Exposure_Number: 17 Target_Name: VCC1104 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 2600 S Special_Requirements: POS TARG -0.115,0.115 END ORBIT EXPAND Comments: Visit_Number: 02 Visit_Requirements: ORIENT 105D TO 105D On_Hold_Comments: Visit_Comments: SAME ORIENT AS 01 NUCLEUS OF GALAXY SHOULD FALL WITHIN WF3. Exposure_Number: 22 Target_Name: VCC1104 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 2400 S Special_Requirements: END ORBIT EXPAND Comments: EXPOSURES 22-27 ARE A 6 STEP SEQUENCE AROUND A HEXAGONAL PATTERN WITH 2.5 PX STEPS Exposure_Number: 23 Target_Name: VCC1104 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 2600 S Special_Requirements: POS TARG 0.115,0.115 END ORBIT EXPAND Comments: Exposure_Number: 24 Target_Name: VCC1104 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 2600 S Special_Requirements: POS TARG 0.115,0.230 END ORBIT EXPAND Comments: Exposure_Number: 25 Target_Name: VCC1104 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 2600 S Special_Requirements: POS TARG 0.0,0.345 END ORBIT EXPAND Comments: Exposure_Number: 26 Target_Name: VCC1104 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 2600 S Special_Requirements: POS TARG -0.115,0.230 END ORBIT EXPAND Comments: Exposure_Number: 27 Target_Name: VCC1104 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 2600 S Special_Requirements: POS TARG -0.115,0.115 END ORBIT EXPAND Comments: Data_Distribution ! 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