! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! Id: 6483 ! ! For help call your Program Coordinator: Mutchler ! Phone: 410-338-1321 , E-mail: mutchler@stsci.edu ! Proposal_Information Title: HST Observations of Galaxies in a Close, Nonmerging Encounter Proposal_Category: GO Scientific_Category: GALAXIES & CLUSTERS Cycle: 6 Investigators PI_name: Debra Elmegreen PI_Institution: Vassar College CoI_Name: Bruce Elmegreen CoI_Institution: IBM Watson Research Center Contact: N ! Y or N (designate at most one contact) CoI_Name: Michele Kaufman CoI_Institution: Ohio State University Contact: N ! Y or N (designate at most one contact) CoI_Name: Elias Brinks CoI_Institution: National Radio Astronomy Observatory Contact: N ! Y or N (designate at most one contact) CoI_Name: Mario Klaric CoI_Institution: Midlands Technical College Contact: N ! Y or N (designate at most one contact) CoI_Name: Curt Struck CoI_Institution: Iowa State University Contact: N ! Y or N (designate at most one contact) CoI_Name: Magnus Thomasson CoI_Institution: Onsala Space Observatory Contact: N ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) WFPC2 observations are requested to obtain UBVI images of IC 2163/NGC 2207, the best example of five well-studied galaxy pairs that exhibit peculiar structures suggestive of recent, close, strong, non--merging encounters. Our ground-based observations of this pair reveal 10^8 M_\odot HI clouds, streaming motions in excess of 100 km s^-1, enhanced gas turbulence, an intrinsically oval disk, possible dwarf galaxy formation in tidal debris, and a large warp, all indicative of extreme tidal agitation but with no sign yet of a nuclear starburst. Our numerical models reproduce these features and suggest that perigalacticon occurred ~40 My ago. HST is needed to resolve a tidal--arm dust lane that is probably a shock front, young star clusters that may be proto--globular, embedded star formation in fast--streaming gas, in 10^8 M_\odot clouds, and in tidal debris, and dust lane structure in a morphologically peculiar bar that may become a nuclear starburst. All of these observations will help clarify how galaxy interactions cause shocks, trigger star formation, and possibly make bars. A partial line--of--sight overlap of IC 2163 also allows a direct measurement of extinction through the galaxy disk of NGC 2207. Questions ! Free format text (please update) Observing_Description: We request 1 orbit for U band (F336W), 1 orbit for B band (F439W), and 1 orbit for both V (F555W) and I (F814W) band observations of each of three fields of view in the galaxy pair IC 2163/NGC 2207, for a total of 9 orbits (F814W is chosen for I because of the good match to Johnson V-I discussed on page 80 of the WFPC2 Handbook Version 3.0). These data will give surface brightness sensitivities of around 22 mag arcsec^-2 (see below), or 27 mag (0.1 arcsec pixel)^-2, allowing the detection of objects like the M_ V=- 11 to -15 proto-globular clusters found by Whitmore & Schweizer (1995, AJ, 109, 960) for the Antennae galaxy (which is at 19 Mpc for H_degrees = 75 km s^-1 Mpc^-1). Four bands are necessary to give both ages and extinctions, and to give intrinsic extinctions in vertically distributed gas like dust lanes. We would like to make observations of 3 fields (each field will be dithered) to get an almost complete mosaic of the two galaxies. Field 1 places the southwest part of the Planetary Camera on the nucleus of IC 2163 and the northeast part of the PC on the eyelid. These are the two most important regions of IC 2163 and they should be observed with the high resolution PC. The eastern arm of the widefield camera then covers the interesting part of the double arm in IC 2163. This field is highest priority because it includes the bar or pseudo-bar in IC 2163, the star formation and dust regions in the eyelid, and the dust/shock lane in the double arm. It also includes 4 giant HI clouds. Field 2 has the Planetary Camera centered on the nucleus of NGC 2207. It includes the western visible and obscured parts of IC 2163 (i.e., the obscured tidal tail) in the eastern lobe of the widefield camera, about half of the southern extension of NGC 2207 (i.e., the tidal debris) in the southern lobe, the radio continuum ridge in NGC 2207, and 3 giant HI clouds. This is the field that will give the extinction through NGC 2207 plus information on the bar structure and star formation there. Field 2 is second highest priority. Field 3 is centered on the western part of NGC 2207 and includes the galaxy's main disk on the side away from the companion. Field 3 is necessary for a nearly complete map of the galaxy pair, and for a comparison between young clusters and star formation regions in NGC 2207 and IC 2163 (from Fields 1, 2). This field includes 3 massive HI clouds in the main disk and a short tidal tail, pointing to the north, which contains another massive HI cloud and faint optical emission. Real_Time_Justification: No special requirements Supporting ground--based data are already available. Michele Kaufman & Elias Brinks led the VLA mapping of the 5 galaxy pairs in our complete ocular galaxy program: IC 2163/ NGC 2207, NGC 2535/6, NGC 5394/5, NGC 3145/43/PGC 29578, and NGC 5676/60. The observations consisted of a total of 7.5 hours in BnC array, 30 hours in C array, and 13 hours in D array; most of the line and continuum VLA data are reduced. The proposed galaxy pair, IC 2163/NGC 2207, was mapped with 13.5''*12'' and 5.25 km s^-1 resolution, and the results published (references above). The CO observations for the ocular study were made by Thomasson, who mapped NGC 2535, 5394, and 5676 with CO J=1-0 at Onsala and NGC 3145 with CO J=2-1 and 1-0 at SEST. A pilot study of IC 2163/NGC 2207 was made with CO J=1-0 and 2-1 at SEST; further observations to make a complete map of this pair are scheduled for December 1995. Ground-based optical observations and data reductions for most of the galaxies pairs have been completed by D. & B. Elmegreen, using the Burrell Schmidt at KPNO (deep broad-band images) and by C. Struck & P. Appleton at Iowa State's Fick Observatory (broad-band and H$\alpha$ images with a wide-field CCD camera). H-J Deeg took some images of IC 2163/NGC 2207 for us at the 24'' Capilla Peak telescope in New Mexico. Vera Rubin also gave us prints of an H$\alpha$ plate from Rubin & Ford (1983), and a blue-band plate with a 90--minute exposure obtained by her with the CTIO 4--m telescope in the early 1970's. These latter two images are in our 1995 publication. Vera Rubin, Kirk Borne, and Charles Peterson (unpublished) also provided spectroscopic H$\alpha$ velocity data along 13 slits covering IC 2163/NGC 2207. The velocities were found to agree very well with the HI velocities (Elmegreen et al.\ 1995a). Calibration_Justification: ! Move appropriate text from Real_Time_Justification The observing times are calculated from equation (6-1) in the 1995 WFPC2 book, p. 66, using the integrals in table 6.2 for the selected filters, and also using the WWW exposure time calculator. We have 54 minutes of visibility per orbit. Then the first orbit consists of: target acquisition (7m7s), F439W box dither (400s x 4), overhead. This gives 26.6 minutes in B. The second orbit gives the same result for U, given the necessity of quantizing the exposures into 400s each. The apparent blue magnitude m(B) is 12.55 for IC 2163; its axis ratio is 2.35 and its radius R(25) is 1.51'. These give an overall surface brightness of 21.6. A single exposure of 400s provides a S/N of 2.4 per pixel, and we will have 4 exposures. Since B-V=.6 for this galaxy, we have V=21 mag and so 400s gives a S/N of 8.3. The third orbit is split between V and I, with line dithering to give 2x400s on each. Note that the three fields overlap, so that we have even more exposure time on the central regions of greatest interest, while providing a complete coverage of the prominent optical structures and possible dwarf galaxies. Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number:1 Target_Name:IC2163-NUC Alternate_Names: Description:GALAXY,SPIRAL,INTERACTING GALAXY Position: ! Most common specification format is RA=6H16M29.00S+/-0.3", ! RA=0H 0M 0.00S +/- 0S, DEC=-21D22'27.0"+/-0.3", ! DEC=0D 0' 0.0" +/- 0", PLATE-ID=04LS ! PLATE-ID=0000 Equinox:J2000 RV_or_Z:V=2756 RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux:B=12.55+/-.14,B-V=.63+/-.03 ! Include at least V and B-V Comments: Fixed_Targets ! Section 5.1 Target_Number:2 Target_Name:NGC2207-NUC Alternate_Names: Description:GALAXY,SPIRAL,INTERACTING GALAXY Position: ! Most common specification format is RA=6H16M23.70S+/-0.3", ! RA=0H 0M 0.00S +/- 0S, DEC=-21D22'24.0"+/-0.3", ! DEC=0D 0' 0.0" +/- 0", PLATE-ID=04LS ! PLATE-ID=0000 Equinox:J2000 RV_or_Z:V=2745 RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux:B=11.59+/-.22,B-V=.68+/-.01 ! Include at least V and B-V Comments: Fixed_Targets ! Section 5.1 Target_Number:3 Target_Name:NGC2207-NW Alternate_Names: Description:GALAXY,SPIRAL,INTERACTING GALAXY Position: ! Most common specification format is RA=6H16M21.30S+/-0.3", ! RA=0H 0M 0.00S +/- 0S, DEC=-21D22'27.0"+/-0.3", ! DEC=0D 0' 0.0" +/- 0", PLATE-ID=04LS ! PLATE-ID=0000 Equinox:J2000 RV_or_Z:V=2745 RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux:V=11.59+/-.12,B-V=.68+/-0.01 ! Include at least V and B-V 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 327D TO 337D ! ORIENTation TO FROM ! ORIENTation TO FROM NOMINAL ! SAME ORIENTation AS ! CVZ ! PARallel ! SCHEDulability ! AFTER [BY [TO ]] ! AFTER ! BEFORE ! BETWEEN AND ! GROUP WITHIN