7457( 5) - 04/30/98 15:14 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7457 Version: 5 Check-in Date: 30-Apr-1998 15:12:06 1.Proposal Title: Warm Molecular Hydrogen in Cluster Cooling Flow Nebulae ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Megan Donahue Space Telescope Science Institute CoI: Richard Elston University of Florida N CoI: Mark Voit Space Telescope Science Institute N CoI: Phillip Maloney University of Colorado N CoI: William Sparks Space Telescope Science Institute N ------------------------------------------------------------------------------------ 5. Abstract We propose to obtain narrow-band NICMOS images of H_2 gas associated with the emission-line nebulae in cluster cooling flows. The intracluster gas at the centers of many clusters of galaxies can cool within a Hubble time, prompting the suggestion that the ICM in these clusters cools and flows towards the center, where it subsequently condenses. The central galaxies of clusters suspected to harbor such ``cooling flows'' frequently display luminous, extended emission line nebulae, apparently ionized by hot, young stars. Significant star formation is occuring in the central galaxies of these clusters, but at rates no more than 10\ observations. Recent IR spectroscopic observations of clusters with optical line emission have shown that they invariably emit H_2 vibrational lines characteristic of ~ 2000 K molecular gas. Somehow molecular gas is accumulating at the centers of these clusters and turning into stars at rates that can be comparable to those in starburst galaxies. We propose to investigate the spatial distribution and morphology of the warm molecular gas using NICMOS narrow-band imaging. These images will reveal the relationships between the warm molecular component in these clusters and the ionized gas, the blue starlight, and the radio sources. ------------------------------------------------------------------------------------ 7457( 5) - 04/30/98 15:14 - [ 2] Observations Description ------------------------ Target Selection and Description: Why These 3 Targets? We have chosen targets in which H_2 has already been spectroscopically detected in them, and they are bright enough to study with modest exposure times. NGC1275, the brightest target, is somewhat problematic. It is the nearest massive cooling flow, with an inferred cooling rate of ~200 solar masses/yr (Edge & Stewart 1991 MNRAS 252 414). However, it is rather atypical for a cooling flow, despite its reputation as the prototypical cooling flow. There is an AGN in its center, and a distinct high-velocity collision occurring off-nucleus. It is also the only CF cluster detected so far in CO emission (mapped recently by Braine et al 1995 A&A, 293, 315.) Therefore we propose to observe two additional, more typical cooling flow cluster nebulae that are undetected in CO but still bright in H_2: Abell 2597 and PKS0745-191. These two have among the most luminous 1-0 S(1) emission observed by Elston and Maloney and they have redshifts that place very high equivalent width emission lines of H_2 within narrow band NICMOS filters. Both Abell 2597 and PKS0745-191 are classic massive cooling flows. Their X-ray cooling rates are 370 (Crawford et al 1989 MNRAS 236 277) and 700 M_odot yr^-1 (Edge & Stewart 1991). Star formation in all 3 systems span 20-40h_50^-2 M_odot yr^-1 (McNamara 1996, in Cluster Cooling Flows, Haifa). OII emission line and broad band imaging, taken with WFPC2, exist for A2597. We propose to obtain a LRF image and continuum image with WFPC2 for PKS0745-191. These images will allow us to directly compare, at similar resolution, the optical emission-line gas and the molecular gas. In NGC1275, we have WFPC2 LRF observations that show that H Alpha emission line gas surrounds the radio jet axis, as well as extensive loops, filaments, and patches of emission. Here the radio jet is clearly interacting strongly with the ambient gas and shocking it into emission. Jet/gas interactions may als be responsible for inducing star formation, and could be contributing to the presence of star formation in these CF clusters. The H_2 emission appears to be coming from the same region; we will determine whether the molecular gas is co- spatial with the jet or anticorrelated with the jet, as the X-ray emitting gas is. Alternatively, the emission may be coming from filaments close to the nucleus. A2597 also has a small double-lobed radio source, presumably powered by a jet (Sarazin et al. 1995, ApJ, 447, 559). PKS0745-191, on the other hand, is an amorphous radio source without any radio evidence for jet activity in the core (Baum & O'Dea 1991 MNRAS, 250, 737). Observation Plan: Our plan is to acquire high signal-to- noise observations of molecular hydrogen lines and continuum through the NICMOS narrow-band filters and H-band filters, then scale the H-band image to remove the galaxy continuum. The H-band filter is broad enough and the lines are sufficiently weak that line emission can not significantly contaminate the H- band image. The molecular hydrogen lines are in a spectral region where the thermal emission from the telescope is important, so we will subtract this background by chopping on and off source. For NGC1275, we will use a throw of at least 120", and for the more distant sources PKS0745-191 and A2597 we will chop 45". Since optical emission line images are not available in the archive for PKS0745-191, we will acquire those here. The signal to noise required in the line+continuum filter and in the continuum filter must be of order 100 to achieve a S/N of about 10 (per relevant scale, which for our purposes is per pixel) in the resulting line image. We used the Web exposure estimator tool to derive total exposure times. Since we must chop, stay below the saturation limits, and fit exposures into finite orbits, we must divide these total exposure times into separate exposures, each requiring overheads for slew and readout. For NGC1275, the line of interest is the H_2 1-0 S(1) line at rest 2.12 micron, redshifts into the F216N bandpass. For PKS0745-191 and A2597, the 1-0 S(3) line at 1.9561 micron redshifts into the F215N and F212N filters, respectively. In Elston & Maloney's spectrum of NGC1275 (Figure 1) note that the 1-0 S(3) is nearly as bright as the 1-0 S(1) line. Typical equivalent widths for H_2 lines in these sources are 35 Angstrom. The continuum images will use the F187W filter for NGC1275 and the F160W filter for PKS0745-191 and A2597. NGC1275 is substantially brighter than the other two sources, so to minimize our exposure time requirements, we have originally chose camera 2 for NGC1275 and camera 3 for A2597 and PKS0745. We have revised our SNR estimates given the newest low backgrounds, and we have changed our program to use Camera 2 alone. Total Exposure Times Required for S/N=100 Imaging Target z H2 Flux (erg/s/ EQW F_Nu t(line) t(H band) Orbits (um) cm^2/arcsec^2) Ang. Jy sec sec Req. NGC1275 0.018 2.159 5(-14) 40 2.2(-2) 1, 000 100 2 PKS0745 0.103 2.157 6(- 15) 40 2.3(-3) 4, 000 100 6* A2597 0.083 2.117 3(-15) 45 1.0(-3) 10, 000 200 10 *Including one orbit for a WFPC2 image of the optical emission line region. We will split the long exposures into background limited exposures of equal length. For the molecular hydrogen imaging, we will require as much time off- source as on to remove background. The chopping will add overhead to each observation. For NGC1275, the orbit length is 54 minutes. We can do 4 on-source and 4 off-source 200 second exposures in one orbit, 2 more each in the next, and obtain 2 100 second continuum exposures, for a total of 2 orbits. For PKS0745, we will obtain 16 total 500 second line+continuum exposures, both on and off source, requiring 4 orbits. In order to have HAlpha emission line images with similar resolution, we will also need one more orbit to acquire a WFPC2 LRF image. 3x600 second images will be adequate, with a continuum image in F439W of 180 seconds. (V=17.3 mag/arcsec^2, equivalent width of H Alpha alone is 80 Angstrom.) The other two targets already have HST emission-line imaging available. For A2597, we will acquire 20 1000-second exposures and a 200 second continuum image in 10 orbits. Donahue will lead the project and coordinate the reduction and data analysis. Elston and Maloney are experienced infrared observers, and will play a major role in Phase II and reductions. Sparks has ample experience with the WFPC2 LRF, and is now the NICMOS group leader. Voit and Maloney will lead the theoretical analysis and interpretations. Both of them have records of expertise in the physics of molecular gas. Real Time Justification ----------------------- None. Spectroscopic near infrared observations are already in hand. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 7457( 5) - 04/30/98 15:14 - [ 3] Data Distribution Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7457( 5) - 04/30/98 15:14 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC1275 GALAXY, BCM, COOLING RA=03H 19M 48.26S +/- 0.3S, J2000 Z=0.018 V = 12.6 FLOW, EMISSION LINE DEC=41D 30' 42.6" +/- 1", PLATE- NEBULA, NUCLEUS ID=02RZ 2 PKS0745-191 GALAXY, BCM, COOLING RA=07H 47M 31.3S +/- 0.3S, DEC=- J2000 Z=0.1028 V = 18 FLOW, EMISSION LINE 19D 17' 39.8" +/- 1", PLATE- NEBULA, NUCLEUS ID=02N7 3 ABELL2597 GALAXY, BCM, COOLING RA=23H 25M 19.7S +/- 0.3S, DEC=- J2000 Z=0.082 V = 15.4 FLOW, EMISSION LINE 12D 7' 26.5" +/- 1", PLATE- NEBULA, NUCLEUS ID=00WQ 7457( 5) - 04/30/98 15:14 - [ 5] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC1275 NIC2 MULTIAC NIC2 F216N pattern=spiral-dith-chop, 1 DEF CUM num-pos=12,dith-size=0.5, chop-size=120,samp-seq=step128, nsamp=11,pattern-orient=250 Comments: pattern-orient is chosen to avoid background objects= PA(E from N) + 90 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC1275 NIC2 MULTIAC NIC2 F160W pattern=one-chop,num-pos=2, 1 DEF CUM chop-size=1,samp-seq=step128, nsamp=10 ------------------------------------------------------------------------------------------------------------------------------------ 7457( 5) - 04/30/98 15:14 - [ 6] Visit: 02 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PKS0745-191 NIC2 MULTIAC NIC2 F215N pattern=spiral-dith-chop, 1 DEF CUM num-pos=2,dith-size=0.5, chop-size=35,samp-seq=step256, nsamp=14,pattern-orient=225 Comments: pattern-orient is chosen to avoid background objects ------------------------------------------------------------------------------------------------------------------------------------ 2 PKS0745-191 NIC2 MULTIAC NIC2 F215N pattern=spiral-dith-chop, 1 DEF POS TARG 0.5,-0.5 CUM num-pos=4,dith-size=0.5, chop-size=35,samp-seq=step256, nsamp=15,pattern-orient=225 ------------------------------------------------------------------------------------------------------------------------------------ 3 PKS0745-191 NIC2 MULTIAC NIC2 F215N pattern=spiral-dith-chop, 1 DEF POS TARG -0.5, 0.5 CUM num-pos=2,dith-size=0.5, chop-size=35,samp-seq=step256, nsamp=14,pattern-orient=225 ------------------------------------------------------------------------------------------------------------------------------------ 4 PKS0745-191 NIC2 MULTIAC NIC2 F160W pattern=one-chop,num-pos=2, 1 DEF CUM chop-size=1,samp-seq=step256, nsamp=11 ------------------------------------------------------------------------------------------------------------------------------------ 5 PKS0745-191 WFPC2 IMAGE LRF LRF 7237 1 2200.0 ------------------------------------------------------------------------------------------------------------------------------------ 6 PKS0745-191 WFPC2 IMAGE LRF LRF 7237 1 1100.0 ------------------------------------------------------------------------------------------------------------------------------------ 7 PKS0745-191 WFPC2 IMAGE WF4 F439W 1 1100.0 SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 7457( 5) - 04/30/98 15:14 - [ 7] Visit: 03 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ABELL2597 NIC2 MULTIAC NIC2 F212N pattern=SPIRAL-DITH-CHOP, 1 DEF POS TARG 0.5,-0.5 CUM num-pos=2,dith-size=0.5, chop-size=45,samp-seq=step256, nsamp=14,pattern-orient=180 Comments: pattern-orient is chosen to avoid background objects ------------------------------------------------------------------------------------------------------------------------------------ 2 ABELL2597 NIC2 MULTIAC NIC2 F212N pattern=spiral-dith-chop, 1 DEF CUM num-pos=8,dith-size=0.5, chop-size=45,samp-seq=step256, nsamp=15,pattern-orient=180 ------------------------------------------------------------------------------------------------------------------------------------ 7457( 5) - 04/30/98 15:14 - [ 8] Visit: 04 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ABELL2597 NIC2 MULTIAC NIC2 F212N pattern=SPIRAL-DITH-CHOP, 1 DEF POS TARG -0.5, 0.5 CUM num-pos=2,dith-size=0.5, chop-size=45,samp-seq=step256, nsamp=14,pattern-orient=180 ------------------------------------------------------------------------------------------------------------------------------------ 2 ABELL2597 NIC2 MULTIAC NIC2 F212N pattern=SPIRAL-DITH-CHOP, 1 DEF POS TARG 0.5, 0.5 CUM num-pos=6,dith-size=0.5, chop-size=45,samp-seq=step256, nsamp=15,pattern-orient=180 ------------------------------------------------------------------------------------------------------------------------------------ 3 ABELL2597 NIC2 MULTIAC NIC2 F212N pattern=spiral-dith-chop, 1 DEF POS TARG -0.5,-0.5 CUM num-pos=2,dith-size=0.5, chop-size=45,samp-seq=step256, nsamp=14,pattern-orient=180 ------------------------------------------------------------------------------------------------------------------------------------ 4 ABELL2597 NIC2 MULTIAC NIC2 F160W pattern=none,samp-seq=step128, 1 DEF CUM nsamp=12 ------------------------------------------------------------------------------------------------------------------------------------ 7457( 5) - 04/30/98 15:14 - [ 9] Visit: 05 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PKS0745-191 NIC2 MULTIAC NIC2 F215N pattern=XSTRIP-DITH,num-pos=2, 1 DEF POS TARG 0.75,-0.75 CUM dith-size=0.75,samp-seq=step256, nsamp=15,pattern-orient=225 Comments: pattern-orient is chosen to avoid background objects ------------------------------------------------------------------------------------------------------------------------------------ 7457( 5) - 04/30/98 15:14 - [ 10] Summary Form for Proposal 7457 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures NIC2 LRF WF4 ------------------------------------------------------------------------------------------------------------------------------------ Configurations NIC2 WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters pattern=spiral-dith-chop num-pos=12 dith-size=0.5 chop-size=120 samp-seq=step128 nsamp=11 pattern-orient=250 nsamp=10 pattern-orient=225 nsamp=15 nsamp=14 samp-seq=step256 pattern-orient=180 chop-size=45 num-pos=2 num-pos=6 nsamp=12 dith-size=0.75 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG 0.5,-0.5 POS TARG -0.5, 0.5 SAME POS AS 6 POS TARG 0.5, 0.5 POS TARG -0.5,-0.5 POS TARG 0.75,-0.75 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F216N F160W F215N LRF F439W F212N ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC1275 PKS0745-191 ABELL2597 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 7237 ------------------------------------------------------------------------------------------------------------------------------------