Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 2230c Report Date: 09-May-96:16:57 Version: ********** Check-in Date: ********** 1.Proposal Title: DISTANCE TO THE SEYFERT GALAXY NGC 4151 DETERMINED BY PARALLEL OBSERVATIONS WITH THE WFC ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID GALAXIES & CLUSTERS GO Sub Category DISTANCE SCALE ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Dr. Aina Elvius STOCKHOLM OBSERVATORY SWEDEN +46 8 7170380 PROFESSOR ------------------------------------------------------------------------------------ 7. Abstract The nearest Seyfert 1 galaxy NGC 4151 has a rapidly variable nucleus with interesting features. It has been studied extensively by the proposers with IUE and ground-based telescopes. Parameters which we want to derive from the observations, like the dimensions of an accretion disk around a possible black hole and the amount of energy emitted from the active nucleus, depend on the distance to NGC 4151. Therefore it is essential to determine the distance as accurately as possible. Distance estimates based on the redshift (presently 10 to 20 Mpc) are not good enough because of a possible peculiar motion of the same order as the Hubble flow. We propose to use the WFC for exposures of the outer spiral structure and surroundings of NGC 4151 in parallel with observations of the nucleus with another instrument. We intend to search the fields for distance indicators such as globular clusters, HII regions, supergiant stars and Cephied variables and to determine their magnitudes and approximate colours. The distance indicators are too faint to be observed from the ground but should be comfortably measured with the HST. ------------------------------------------------------------------------------------ 8. Scientific Key Words: SEYFERT GALAXY, DISTANCE DETERMINATION, GLOBULAR CLUSTERS ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 0 par: 10.00 10. Num targs pri: 0 par: 4 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 2230c PI: Dr. Aina Elvius Proposal Title: DISTANCE TO THE SEYFERT GALAXY NGC 4151 DETERMINED BY PARALLEL OBSERVATIONS WITH THE WFC ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Dr. Aina Elvius STOCKHOLM OBSERVATORY SWEDEN X Dr. A. Altamore INSTITUTO ASTRONOMICO ITALY X DELL'UNIVERSITA, ROME Prof. Alec Boksenberg ROYAL GREENWICH OBSERVATORY, UK X HAILSHAM Dr. Gordon E Bromage RUTHERFORD AND APPLETON UK X LABORATORY, CHILTON Dr. Jean Clavel ESA IUE OBSERVATORY, MADRID SPAIN X Dr. Robert A Fosbury ST-ECF FRG X Prof. G. C Perola INSTITUTO ASTRONOMICO ITALY X DELL'UNIVERSITA, ROME Dr. Michael V Penston ROYAL GREENWICH OBSERVATORY, UK X CAMBRIDGE Dr. M. A Snijders ASTRONOMISCHES INSTITUT FRG X TUEBINGEN Dr. Marie-Helene Ulrich EUROPEAN SOUTHERN OBSERVATORY FRG X ------------------------------------------------------------------------------------ 3. Description of proposed observations. We propose parallel observations with the WFC when central regions of NGC 4151 are observed with one of the axial SIs. We will use the WFC in a serendipitous mode to search for objects of interest especially suitable distance indicators such as globular clusters, HII regions, luminous stars and Cephied variables. The field covered by the WFC in parallel mode will depend on the instrument used in the primary mode and on the roll angle of the HST. We have identified three main cases: 1. NGC 4151 nucleus in the FOS will permit WFC observations of spiral arms and we expect to find all types of distance indicators mentioned above. The filter F439W will be used to study HII regions and, with F702W, will also be used for colours of other objects for which F555W will be used for V magnitudes. 2.NGC 4151 nucleus in GHRS and an HST roll angle of 175 +/- 15 deg places NGC4156 into the WFC FOV. We propose the same filters as in case 1 but somewhat longer exposures. 3.(If and when FOC/WFPC parallel observations are allowed). NGC 4151 in FOC or in HRS with other roll angles than in case 2 will give WFC fields outside the main structure of the galaxy, making globular clusters the main targets. Filters F555W and F702W are proposed for V magnitudes and colours. In all cases it is essential for the colour measures that the same region be observed with different filters. If it is sometimes possible to make only one exposure of a certain region, the filter F439W is preferred in cases 1 and 2 for studies of HII regions and the filter F555W in case 3 for the identification of non-stellar objects such as globular clusters and for measures of V magnitudes. Observations well outside the main spiral arms are of importance also for statistical studies of foreground Galactic stars which must be considered when stellar objects in the spiral arms of NGC 4151 are studied. Also, in the search for globular clusters, such studies will be of some help. Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. These distance indicators are too faint to be observed from the ground. In order to identify the globular clusters as non-stellar objects and to determine their luminosity function down to about Mv=-5, we need to reach V=27 at the distance of NGC 4151. Possible Cephied variables should be identified to the same magnitude. The deepest pictures of NGC 4151 so far seem to be those published by Arp (1977). He used some of the largest ground-based telescopes and special copying techniques to produce prints reaching down to magnitude 25 (his estimate). The published prints have been used by us for determining suitable WFC fields as mentioned above. This material cannot be used for precise distance determination. Arp has used photographs in red light of the inner structures of NGC 4151 to measure the diameters of some HII regions there. We should like to measure HII regions in the spiral arms, expecting that they will be more representative of the standards used in distance determinations and that their diameters can be measured more precisely with the HST. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. We need to measure at least 25 to 30 globular clusters in order to use a proposed statistical method. As we do not know beforehand where to find these or other distance indicators, we plan for observations of about 6 regions with the WFC in parallel mode, the regions in each of the 3 cases detailed in section 3 above and using 2 or 3 filters for each region we arrive at about 14 exposures. Exposure times will range from 1800 s to 3000 s with most at about 2500 s. As shown in the computer simulations made so far, the 2500 s exposure is expected to show very clearly a globular cluster as a non-stellar object when an integrated absolute magnoiude of -7.4 and a distance of 15Mpc are assumed. We want to reach also clusters about 2 magnitudes fainter. The distance may be more or less than 15Mpc. ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. We plan to make copies of the HST data as they become available so that each institution in our group has a data set. Each of us has access to a VAX computer or SUN workstation on which will be implemented reduction and analysis s/w from STScI and ST-ECF. We are a large group and are used to working together. The CCD frames will be searched for various kinds of objects mentioned in this proposal. As necessary, computer simulations of non-stellar objects will be made for comparison. Magnitudes and colours of identified distance indicators will be determined in the instrumental system and either directly used for distance determination using other HST data obtained in similar programmes or calibrated in terms of standard systems (like U, B, V) by means of calibrations in the HST archive, so that the HST data can be compared with ground-based studies. ------------------------------------------------------------------------------------ 9. Description of previous HST work. A A. Boksenberg GTO program 1222 FOC not closely relevant 1216-1220, 1223, 1225- 1227, 1240 not relevant but same subject area 1245, 1261 not relevant ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Our institutions will provide adequate computing time for reducing the data. The most recent data reduction and analysis s/w will be implemented and continuously updated in our different institutions. ------------------------------------------------------------------------------------ 11. Address Information Page 4 Name: AINA ELVIUS Category: PI Institution: STOCKHOLM OBSERVATORY Address: S-133 36 SALTSJOEBADEN City: State: Zip Code: Country: SWEDEN Telephone: +46 8 7170380 Telex (or e-mail): 12972 SOBSERV S ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 2230c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC4151- GALAXY, AGN, PLATE-ID=01QY, 2000 Z=0.0032 1 V=13 NUCLEUS SEYFERT GALAXY RA=12H 10M 32.518S +/- 0.2", GSC3017-939 DEC=+39D 24' 20.77" +/- 0.2" Comments: SEYFERT NUCLEUS OBSERVED ONLY IN PRIMARY MODE WITH OTHER SI. THE FOLLOWING LINE NUMBERS ARE FOR PARALLEL MODE OBSERVATIONS WITH WFC AND SO THIS TARGET IS NOT REFERENCED IN THE EXPOSURE LOGSHEET FOR THIS PROPOSAL. ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC4151-POS1 EXT-CLUSTER; 2 V = 24 +/- 3 EXT-MEDIUM; EXT-STAR Comments: ANY REGION OBSERVED IN PARALLEL WITH NGC4151 NUCLEUS IN A FOS APER. ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC4151-POS2 EXT-CLUSTER; 2 V = 24 +/- 3 EXT-MEDIUM; EXT-STAR Comments: ANY REGION OBSERVED IN PARALLEL WITH NGC4151 NUCLEUS INCLUDING ALL OR PART OF NGC 4156 (=GSC3017-663, CZ=6700KM/S). EG. GHRS WITH ROLL=175 +/- 15 DEG OR FOC WITH ROLL CLOSE TO 0 DEG. ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC4151-POS3 EXT-CLUSTER; 2 V = 24 +/- 3 GLOBULAR CLUSTER Comments: ANY REGION OBSERVED IN PARALLEL WITH NGC4151 NUCLEUS IN GHRS APER. PROPOSAL 2469 USING GHRS HAS ASKED FOR STEP- TIME=1.0 TO ENABLE WFC PAR. OBS. ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC4151-POS4 EXT-CLUSTER; 2 V = 24 +/- 3 GLOBULAR CLUSTER Comments: ANY REGION OBSERVED IN PARALLEL WITH NGC4151 NUCLEUS IN A FOC APER. (IF AND WHEN THIS OPTION BECOMES AVAILABLE.) ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2230c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 DEFINE NGC4151- WFC IMAGE ANY F555W 1 40M 10 2 1 PAR CASE-1 POS1 ------------------------------------------------------------------------------------------------------------------------------------ 2 ^ NGC4151- WFC IMAGE ANY F439W 1 45M 10 2 1 PAR POS1 SAME POS FOR 2 AS 1 Comments: SLIGHT POSITION DIFFERENCES ARE ACCEPTABLE - AS LONG AS MOST OF THE FIELD IS IN COMMON. ------------------------------------------------------------------------------------------------------------------------------------ 3 ^ NGC4151- WFC IMAGE ANY F702W 1 40M 10 2 2 PAR POS1 SAME POS FOR 3 AS 1 Comments: SLIGHT POSITION DIFFERENCES ARE ACCEPTABLE - AS LONG AS MOST OF THE FIELD IS IN COMMON. ------------------------------------------------------------------------------------------------------------------------------------ 4 DEFINE NGC4151- WFC IMAGE ANY F555W 1 45M 10 2 1 PAR CASE-2 POS2 ------------------------------------------------------------------------------------------------------------------------------------ 5 ^ NGC4151- WFC IMAGE ANY F439W 1 45M 10 2 1 PAR POS2 SAME POS FOR 5 AS 4 Comments: SLIGHT POSITION DIFFERENCES ARE ACCEPTABLE - AS LONG AS MOST OF THE FIELD IS IN COMMON. ------------------------------------------------------------------------------------------------------------------------------------ 6 ^ NGC4151- WFC IMAGE ANY F702W 1 45M 10 2 2 PAR POS2 SAME POS FOR 6 AS 4 Comments: SLIGHT POSITION DIFFERENCES ARE ACCEPTABLE - AS LONG AS MOST OF THE FIELD IS IN COMMON. ------------------------------------------------------------------------------------------------------------------------------------ 7 DEFINE NGC4151- WFC IMAGE ANY F555W 1 45M 10 2 1 PAR CASE-3 POS3 ------------------------------------------------------------------------------------------------------------------------------------ 8 ^ NGC4151- WFC IMAGE ANY F702W 1 45M 10 2 1 PAR POS3 SAME POS FOR 8 AS 7 Comments: SLIGHT POSITION DIFFERENCES ARE ACCEPTABLE - AS LONG AS MOST OF THE FIELD IS IN COMMON. ------------------------------------------------------------------------------------------------------------------------------------ 9 DEFINE NGC4151- WFC IMAGE ANY F555W 1 45M 10 2 1 PAR CASE-4 POS4 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2230c [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 DEFINE NGC4151- WFC IMAGE ANY F702W 1 45M 10 2 1 PAR CASE-4 POS4 SAME POS FOR 10 AS 9 Comments: SLIGHT POSITION DIFFERENCES ARE ACCEPTABLE - AS LONG AS MOST OF THE FIELD IS IN COMMON. ------------------------------------------------------------------------------------------------------------------------------------ 11 USE CASE-1 Comments: WHENEVER PARALLEL OPPORTUNITY ARISES. ------------------------------------------------------------------------------------------------------------------------------------ 12 USE CASE-2 Comments: WHENEVER PARALLEL OPPORTUNITY ARISES. ------------------------------------------------------------------------------------------------------------------------------------ 13 USE CASE-3 Comments: WHENEVER PARALLEL OPPORTUNITY ARISES. ------------------------------------------------------------------------------------------------------------------------------------ 14 USE CASE-4 Comments: WHENEVER PARALLEL OPPORTUNITY ARISES. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 2230c [ 8] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category DISTANCE SCALE ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PAR PAR; SAME POS FOR 2 AS 1 SAME POS FOR 3 AS 1 SAME POS FOR 5 AS 4 SAME POS FOR 6 AS 4 SAME POS FOR 8 AS 7 SAME POS FOR 10 AS 9 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F439W F702W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC4151-NUCLEUS GSC3017-939 NGC4151-POS1 NGC4151-POS2 NGC4151-POS3 NGC4151-POS4 ------------------------------------------------------------------------------------------------------------------------------------