! 6653.prop - Version edited by Ron Downes with changes as recommended ! in CS review by Downes and Keyes. - 3 December, 1996 ! - Corrected by Ray Lucas to fix database problems since ! updates to coords of targets already observed are not ! allowed by the system. A new target had to be defined for ! the spectroscopy part. ! ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6653,v 14.1 1996/12/03 23:01:12 pepsa Exp $ ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6653,v 14.1 1996/12/03 23:01:12 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: Lucas ! Phone: 410-338-4716 , E-mail: lucas@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Name of Phase I Proposal: archive-0688.ford.prop ! Date generated: Fri Dec 22 16:37:12 EST 1995 ! Proposal_Information ! Section 4 Title: Kinematics of Ionized Gas in the Dusty Nuclear Disk in NGC 6251; An Excellent Candidate for a Massive Black Hole Proposal_Category: GO Scientific_Category: GALAXIES & CLUSTERS Cycle: 6 Investigators PI_name: Holland Ford PI_Institution: Johns Hopkins University CoI_Name: Laura Ferrarese CoI_Institution: Space Telescope Science Institute Contact: ! Y or N (designate at most one contact) CoI_Name: Walter Jaffe CoI_Institution: Leiden Observatory Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) We propose to use narrow-band WFPC2 images and FOS spectra to study the morphology and dynamics of the ionized gas in the nuclear disk of the elliptical galaxy NGC 6251. Our aim is to study the disk around the active nucleus, and to establish the presence and mass of a central, massive black hole, following the same procedure that led to a successful detection of black holes in M87 and NGC 4261 (Ford et al. 1994, Harmes et al. 1994, Ferrarese et al. 1996). NGC 6251 is ideal for this type of study; as in M87 and NGC 4261 (Ford et al. 1994, Jaffe et al. 1994), NGC 6251 harbors a small nuclear dust disk (O'Neil and Lynds, 1994), and is a very powerful radio galaxy. The minor axis of the dust disk is aligned with the spectacular 100 kpc radio jet and the axis of the Mpc scale radio lobes (Waggett, Warner, and Baldwin, 1977), an alignment also found in M87 and NGC 4261, suggesting that the NGC 6251 disk is causally related to the nuclear activity. Nuclear disks of ionized gas and dust provide a powerful way to measure the central potential. Indeed, HST/FOS spectra of M87 and NGC 4261 (Harms et al. 1994, Ferrarese et al. 1996) allowed us to study the orbital motion of the ionized gas in the nuclear disks, and enabled measurement of central masses of 2.4X10^9 solar masses and 1.2X10^9 solar masses in the two galaxies. Questions ! Free format text (please update) Observing_Description: WFPC2 Observations. In order to obtain the highest possible spatial resolution, NGC 6251 will be centered in the PC1. At a radial velocity of 6900 km/s, the redshifted Halpha emission is expected at 6713 Angstrom, wavelength region which is covered by the F673N narrow band filter. The filter transmission is highest at the wavelength at which the Halpha emission is expected. It is vital that two off-band images will be taken in regions not contaminated by line emission and on either side of the Halpha emission. There are two compelling reasons for having two off-band images: first, it will allow us to estimate color corrections between the off-band and the on-band images, allowing a more accurate subtraction of the stellar continuum than would be possible with the use of only one off-band image; second, we will use the off-band images to obtain a color map of the nuclear region and to identify dust structures. We will use the F547M and F814W filters to obtain an off-band image on the blue and red sides of the H alpha emission respectively. In order to facilitate cosmic ray removal, the images in each filter will be split into two exposures. Keeping into account the time needed for Guide Star acquisition and the overhead associated with each observation, three full orbits are necessary to complete the proposed WFPC2 observations. FOS Observations. In planning the FOS observations of NGC 6251, we followed closely the procedure adopted for our observations of NGC 4261, which proved successful in the detection of a ~ 10^9 solar masses black hole. Our models of the light and mass distribution show that the definitive signature of a massive black hole will be a transition to a rising Keplerian rotation curve for r < 0."3. We propose to use the FOS 0."09 aperture with the G780H grating, covering the redshifted Halpha+[NII] spectral region, to map the rotation curve in the disk in the crucial region r < 0."3. The final position of the FOS apertures will be defined after the exact morphology of the Halpha emission is determined using the WFPC2 images proposed here. If the emission is uniformly distributed, the pattern adopted will include a 3X3 grid centered on the nucleus and with axes aligned with the major and minor axes of the disk, plus 4 additional positions along the major and minor axes of the disk, on either side of the nucleus, placed just outside the 3X3 grid. The same pattern was used successfully for the FOS observations of NGC 4261. Since no optical spectra or emission line images of NGC 6251 are available, an accurate calculation of the exposure time needed for the spectroscopy will have to wait until the WFPC2 images proposed here will be taken and properly analyzed. Until then, we are forced to base our calculations on our past experience with M87 and NGC 4261. The most optimistic assumption we can make is that the H Alpha flux in the NGC 6251 disk is the same as observed in NGC 4261. This is likely to be an upper limit to the flux, since NGC 6251 is at least 3 times further than NGC 4261; however, the radio emission and the radio jet in NGC 6251 are stronger than in NGC 4261, leading us to expect an intrinsically higher Halpha luminosity. Our experience with NGC 4261 shows that a S/N of 10 at the peak of the [NII]6584+Halpha emission line, is necessary to resolve a Keplerian rise in the rotation curve due to a nuclear black hole with mass larger than 5X10^8 solar masses in the nucleus of NGC 6251. NGC 4261 was mapped with the FOS/G570H at 13 different aperture position, using an exposure time of 2100 seconds for each exposure. We conclude that this is the minimum amount of time that should be spent at each aperture position for NGC 6251. If the analysis of the WFPC2 images shows that the flux in Halpha is lower than for NGC 4261, we will reduce the number of aperture positions in order to achieve the desired S/N ratio. In the most pessimistic case in which the Halpha flux is too low or the Halpha emission is not resolved, we will use all the time allocated to the FOS part of this program to obtain only one spectrum at the nuclear position. Taking into account a 6 minutes overhead associated with each exposure and the time needed for Guide Star acquisition, each of the 13 aperture positions will fill about 80% of one orbit. The ensamble of 13 spectra will therefore require 11 orbits. The nucleus of NGC 6251 is unresolved (O'Neil and Lynds 1995) and sits on a fairly homogeneous background (the dust disk), therefore the acquisition procedure will consist of a binary acquisition in the 1."0 aperture (the color of the nucleus will be derived from the WFPC2 images proposed as the first stage of this program), followed by a standard two stage peak up in the 0."3 and 0."1 apertures. The entire procedure will take two orbits (giving the overhead times tabulated at pages 30 and 31 of the FOS Instrument Handbook). A very similar procedure was executed successfully for the target acquisition of the NGC 4261's nucleus. Therefore, a total of 11 + 2 = 13 orbits are required for the spectroscopy. Real_Time_Justification: None Calibration_Justification: ! Move appropriate text from Real_Time_Justification None Additional_Comments: None Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: NGC6251-NUC Alternate_Names: Description: GALAXY,ELLIPTICAL,RADIO GALAXY Position: RA=16H 32M 31.85S +/- 0.04S, DEC=82D 32' 16.3" +/- 0.5", Plate-ID=01JN Equinox: J2000 RV_or_Z: V=+6900 RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: SURF(R)=19.5+/-0.5 V-R=0.6 Comments: Plate-ID is the one from which the GASP finder charts are made and from which the guide stars should be taken since the only other calibrated GS plate on which the target appears is one on which the target is at an extreme edge of the plate. It is much more centrally located on 01JN which corresponds to region N009. Target_Number: 2 Target_Name: NGC6251-FOS-NUC Alternate_Names: Description: GALAXY,ELLIPTICAL,RADIO GALAXY Position: RA=16H 32M 32.16S +/- 0.006S, DEC=82D 32' 16.59" +/- 0.1" Equinox: J2000 RV_or_Z: V=+6900 RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=18.72+/-0.14 V-I=1.17+/-0.23 F(6725)=2.6+/-0.3E-16 Comments: Updated coords based on WFPC2 EARLY ACQ in Visit 1. Target_Number: 3 Target_Name: NGC6251-OFF1 Description: GALAXY,ELLIPTICAL,RADIO GALAXY Position: XI-OFF=0.0897"+/-0.01", ETA-OFF=-0.0078"+/-0.01", FROM 2 Equinox: J2000 RV_or_Z: V=+6900 Flux: V-I=1.17+/-0.23 F(6725)=6.2+/-0.6E-17 Comments: Target_Number: 4 Target_Name: NGC6251-OFF2 Description: GALAXY,ELLIPTICAL,RADIO GALAXY Position: XI-OFF=0.1793"+/-0.01", ETA-OFF=-0.0157"+/-0.01", FROM 2 Equinox: J2000 RV_or_Z: V=+6900 Flux: V-I=1.17+/-0.23 F(6725)=7.5+/-0.8E-18 Comments: Target_Number: 5 Target_Name: NGC6251-OFF3 Description: GALAXY,ELLIPTICAL,RADIO GALAXY Position: XI-OFF=-0.0897"+/-0.01", ETA-OFF=0.0078"+/-0.01", FROM 2 Equinox: J2000 RV_or_Z: V=+6900 Flux: V-I=1.17+/-0.23 F(6725)=6.2+/-0.6E-17 Comments: Target_Number: 6 Target_Name: NGC6251-OFF4 Description: GALAXY,ELLIPTICAL,RADIO GALAXY Position: XI-OFF=-0.1793"+/-0.01", ETA-OFF=0.0157"+/-0.01", FROM 2 Equinox: J2000 RV_or_Z: V=+6900 Flux: V-I=1.17+/-0.23 F(6725)=7.5+/-0.8E-18 Comments: Target_Number: 7 Target_Name: NGC6251-OFF5 Description: GALAXY,ELLIPTICAL,RADIO GALAXY Position: XI-OFF=0.0078"+/-0.01", ETA-OFF=0.0897"+/-0.01", FROM 2 Equinox: J2000 RV_or_Z: V=+6900 Flux: V-I=1.17+/-0.23 F(6725)=6.2+/-0.6E-17 Comments: Target_Number: 8 Target_Name: NGC6251-OFF6 Description: GALAXY,ELLIPTICAL,RADIO GALAXY Position: XI-OFF=0.0157"+/-0.01", ETA-OFF=0.1793"+/-0.01", FROM 2 Equinox: J2000 RV_or_Z: V=+6900 Flux: V-I=1.17+/-0.23 F(6725)=7.5+/-0.8E-18 Comments: Target_Number: 9 Target_Name: NGC6251-OFF7 Description: GALAXY,ELLIPTICAL,RADIO GALAXY Position: XI-OFF=-0.0078"+/-0.01", ETA-OFF=-0.0897"+/-0.01", FROM 2 Equinox: J2000 RV_or_Z: V=+6900 Flux: V-I=1.17+/-0.23 F(6725)=6.2+/-0.6E-17 Comments: Target_Number: 10 Target_Name: NGC6251-OFF8 Description: GALAXY,ELLIPTICAL,RADIO GALAXY Position: XI-OFF=-0.0157"+/-0.01", ETA-OFF=-0.1793"+/-0.01", FROM 2 Equinox: J2000 RV_or_Z: V=+6900 Flux: V-I=1.17+/-0.23 F(6725)=7.5+/-0.8E-18 Comments: Target_Number: 11 Target_Name: NGC6251-OFF9 Description: GALAXY,ELLIPTICAL,RADIO GALAXY Position: XI-OFF=0.0975"+/-0.01", ETA-OFF=0.0818"+/-0.01", FROM 2 Equinox: J2000 RV_or_Z: V=+6900 Flux: V-I=1.17+/-0.23 F(6725)=1.0+/-0.1E-17 Comments: Target_Number: 12 Target_Name: NGC6251-OFF10 Description: GALAXY,ELLIPTICAL,RADIO GALAXY Position: XI-OFF=-0.0818"+/-0.01", ETA-OFF=0.0975"+/-0.01", FROM 2 Equinox: J2000 RV_or_Z: V=+6900 Flux: V-I=1.17+/-0.23 F(6725)=1.0+/-0.1E-17 Comments: Target_Number: 13 Target_Name: NGC6251-OFF11 Description: GALAXY,ELLIPTICAL,RADIO GALAXY Position: XI-OFF=-0.0975"+/-0.01", ETA-OFF=-0.0818"+/-0.01", FROM 2 Equinox: J2000 RV_or_Z: V=+6900 Flux: V-I=1.17+/-0.23 F(6725)=1.0+/-0.1E-17 Comments: Target_Number: 14 Target_Name: NGC6251-OFF12 Description: GALAXY,ELLIPTICAL,RADIO GALAXY Position: XI-OFF=0.0818"+/-0.01", ETA-OFF=-0.0975"+/-0.01", FROM 2 Equinox: J2000 RV_or_Z: V=+6900 Flux: V-I=1.17+/-0.23 F(6725)=1.0+/-0.1E-17 Comments: ! This is a template for a single visit containing a single exposure ! Repeat exposure and visit blocks as needed Visits ! Section 6 Visit_Number: 1 Visit_Requirements: ! Section 7.1 ! Uncomment or copy visit level special requirements needed ! Most of these requirements (including ORIENT) will limit scheduling ! PCS MODE [Fine | Gyro] ! GUIDing TOLerance ! DROP TO GYRO IF NECESSARY [NO REACQuisition] ! ORIENTation TO ! ORIENTation TO FROM ! ORIENTation TO FROM NOMINAL ! SAME ORIENTation AS ! CVZ ! PARallel ! SCHEDulability ! AFTER [BY [TO ]] ! AFTER ! BEFORE ! BETWEEN AND ! GROUP WITHIN