8106( 3) - 10/18/99 15:37 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8106 Version: 3 Check-in Date: 16-Feb-1999 15:28:05 1.Proposal Title: The mass of the black hole in Cygnus A ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Clive Tadhunter University of Sheffield CoI: Dr David Axon University of Manchester N CoI: Dr Neal Jackson University of Manchester N CoI: Dr Chris Packham La Palma Observatory N ------------------------------------------------------------------------------------ 5. Abstract Although supermassive black holes are thought to be the main power source for the jets and active components of radio galaxies, the relationship between the masses of the black holes, the bulges of the host galaxies, and the radio activity are not understood with any certainty. Part of the problem has been the lack of suitable dynamical tracers in the nuclei of the radio source host galaxies. However, using HST imaging observations we have recently detected a high surface brightness disk structure at the centre of the archetypal powerful radio galaxy Cygnus A. We now propose to use STIS measurements of the emission line kinematics in the disk to measure the mass of the core of the galaxy, and thereby test the idea that powerful radio sources are only associated with the most massive black holes (M_bh > 10^9 M_\odot) in the host galaxies with the most massive galaxy bulges. Requiring only 5 orbits of HST time, this project is fundamental to our general understanding of the en er gy generation mechanisms in powerful radio galaxies. These observations will represent the first attempt to map the kinematics of the ionized gas in detail on a sub-kpc scale in a powerful FRII radio galaxy. Given the requirement for high spatial resolution long-slit spectroscopy across the core of the galaxy, this project can only be done with STIS on the HST. ------------------------------------------------------------------------------------ 8106( 3) - 10/18/99 15:37 - [ 2] Observations Description ------------------------ As mentioned in the scientific case, we will cover the entire high surface brightness core structure with five parallel slit positions, and with the slit oriented perpendicular to the radio axis. Moving from south east to north west along the radio axis (PA105), the slit centres will be placed -0.2,-0.1, 0.0, 0.1, 0.2 arcseconds relative to the continuum core source. We have accurate astrometry for both the core source and offset stars from our previous WFPC2 imaging campaign. Use of the 52*0.1 arcsec slit and the G430L grating will provide adequate spectral resolution and the spatial resolution (perpendicular to the slit). The spectral resolution resulting from this configuration will be ~7Angstrom (300 km s^-1 at redshifted OIIILambda5007), and we will be able to cover [OIII]5007, 4959 and HBeta and [OII]3727 in the same spectrum. We choose [OIII]5007 because it is the brightest line emitted by the high surface brightness core structure and it does not suffer from contam in ation by scattered quasar broad lines, which is a potential problem for HAlpha (Ogle et al. 1997). At each slit position we will perform a sub-pixel offset (dither) along the slit to improve the spatial sampling and resolution. Thus, with two exposures per dither position (to facilitate cosmic ray removal) we will require 4 exposures per orbit at each slit position. We aim for a S/N>5 per 2.7 Angstrom spectral and 0.05 arcsec spatial pixel across the OIIILambda5007 profile. The mean OIII surface brightness in the central V structure estimated from our WFPC2 images is SB_OIII = 5times10^-14 erg s^-1 cm^- 2 sq.arcsec^-1. Using the sensitivity and slit throughput values from version 2 of the STIS manual, and assuming that the line flux is spread over 3 spectral pixels, we find that we achieve a S/N of more than 10 per pixel in 2400 seconds integration (1 orbit allowing for overheads).The equivalent S/N in the integrated line flux per spatial pixel is 20 for the same exposure t im e. Allowing 0.5 orbits for initial offset star acquisition, peaku p, and offsetting to the target, we will require a total of 5 orbits to complete observations at 5 slit positions (note that the exposure time is only 1200 for the lowest priority slit position used in the first orbit). Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: NO Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8106( 3) - 10/18/99 15:37 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 3C405-OFFSET STAR RA=19H 59M 27.6083S +/- 0.009S, J2000 V = 19.4+/-0.2 DEC=40D 43' 55.744" +/- 0.1", TYPE=K PLATE-ID=003S Comments: This is the offset star. Accurate positional offsets to the core region of Cygnus A (for 3C405-POS1, 3C405- POS2 rtc...) have been determined from previous WFPC2 images using the metric task (with headers of the WFPC2 images updated using the uchcoord task). The V- band magnitude and spectral type of the star have been estimated on the basis of WFPC2 and NICMOS photometry. The F555 WFPC2 image u2cn0104t was use to determine the slit offsets. The plate name has been determined using the dominant guide star ID from the header of this image (DGESTAR 0314101562), following the procedure outlined in Appendix A of the guide to target aquisition. 2 3C405-POS1 GALAXY, RADIO GALAXY RA-OFF=0.7511S+/- 0.01S, DEC- J2000 V = 16.0+/-0.5 OFF=6.548"+/- 0.07", FROM 1, PLATE-ID=003S Comments: This is the first (most easterly) slit position. Accurate positional offsets to the core region of Cygnus A for this and other offset positions (3C405- POS1, 3C405-POS2 etc...) have been determined from previous WFPC2 images using the metric task in SDSDAS (with headers of the WFPC2 images updated using the uchcoord task). The adjacent slits are offset by 0.1 arcseconds in RA (0.088 seconds of time for the celestial latitude of Cygnus A), this corresponds to an offset of 0.096 arcseconds perpendicular to the slit for a slit at PA15 (optimal slit position), and an offset of 0.087 arcseconds perpendicular to the slit for PA30. 3 3C405-POS2 GALAXY, RADIO GALAXY RA-OFF=0.7423S+/- 0.01S, DEC- J2000 V = 16.0+/-0.5 OFF=6.548"+/- 0.07", FROM 1, PLATE-ID=003S Comments: This is the second slit position. 4 3C405-POS3 GALAXY, RADIO GALAXY RA-OFF=0.7335S+/- 0.01S, DEC- J2000 V = 16.0+/-0.5 OFF=6.548"+/- 0.07", FROM 1, PLATE-ID=003S Comments: This is the third (central) slit position. 5 3C405-POS4 GALAXY, RADIO GALAXY RA-OFF=0.7247S+/- 0.01S, DEC- J2000 V = 16.0+/-0.5 OFF=6.548"+/- 0.07", FROM 1, PLATE-ID=003S Comments: This is the fourth slit position. 6 3C405-POS5 GALAXY, RADIO GALAXY RA-OFF=0.7168S+/- 0.01S, DEC- J2000 V = 16.0+/-0.5 OFF=6.548"+/- 0.07", FROM 1, PLATE-ID=003S Comments: This is the fifth (most westerly) slit position. 8106( 3) - 10/18/99 15:37 - [ 4] Visit: 01 Visit Priority: Visit Requirements: ORIENT 230D TO 250D ORIENT 50D TO 70D On Hold Comments: Additional Comments: Following initial aquisition and peakup on an offset star (exposures 10, 20), the slit is offset in turn to 5 parallel slit positions which cover the whole core region of Cygnus A (exposures 30, 40, 50, 60, 70). For the four last slit positions (1 orbit each), the telescope will be dithered by 10.5 pixels along the slit (2 point dither), in order to attempt to improve the spatial resolution. The optimal orientation is PA15 or PA195 --- perpendicular to the radio axis. The requested ORIENTs will cover a range of +/-10 degrees around the optimal position. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 3C405-OFFSE STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 20 S ONBOARD ACQ FOR 20 T CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 3C405-OFFSE STIS/C ACQ/PEA 52X0.1 MIRROR 1 60 S ONBOARD ACQ FOR 30, 40, T CD K 50, 60, 70 ------------------------------------------------------------------------------------------------------------------------------------ 30 3C405-POS1 STIS/C ACCUM 52X0.1 G430L 4300 CR-SPLIT=2 1 1350 S CD ------------------------------------------------------------------------------------------------------------------------------------ 40 3C405-POS2 STIS/C ACCUM 52X0.1 G430L 4300 PATTERN=ALONG-SLIT,NUM-POS=2, 1 1350 S CD STEP-SIZE=0.525, PATTERN-DIRECTION=PLUS,CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ 50 3C405-POS3 STIS/C ACCUM 52X0.1 G430L 4300 PATTERN=ALONG-SLIT,NUM-POS=2, 1 1350 S CD STEP-SIZE=0.525, PATTERN-DIRECTION=PLUS,CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ 60 3C405-POS4 STIS/C ACCUM 52X0.1 G430L 4300 PATTERN=ALONG-SLIT,NUM-POS=2, 1 1350 S CD STEP-SIZE=0.525, PATTERN-DIRECTION=PLUS,CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ 70 3C405-POS5 STIS/C ACCUM 52X0.1 G430L 4300 PATTERN=ALONG-SLIT,NUM-POS=2, 1 1350 S CD STEP-SIZE=0.525, PATTERN-DIRECTION=PLUS,CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ 8106( 3) - 10/18/99 15:37 - [ 5] Summary Form for Proposal 8106 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT CR-SPLIT=2 PATTERN-DIRECTION=PLUS STEP-SIZE=0.525 NUM-POS=2 PATTERN=ALONG-SLIT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 230D TO 250D ORIENT 50D TO 70D ONBOARD ACQ FOR 20 ONBOARD ACQ FOR 30, 40, 50, 60, 70 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430L ------------------------------------------------------------------------------------------------------------------------------------ Target Names 3C405-OFFSET 3C405-POS1 3C405-POS2 3C405-POS3 3C405-POS4 3C405-POS5 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 4300 ------------------------------------------------------------------------------------------------------------------------------------