! $Id: 5302,v 5.1 1994/07/27 16:21:11 pepsa Exp $ coverpage: title_1: THE SIZE AND MORPHOLOGY OF NORMAL GALAXIES AT Z~3 sci_cat: GALAXIES & CLUSTERS sci_subcat: DISTANT GALAXIES proposal_for: GO pi_fname: PALLE pi_lname: MOLLER pi_inst: 3470 pi_phone: 410 338 1018 hours_pri: 16.00 num_pri: 1 wf_pc: Y ! end of coverpage abstract: line_1: Using the ESO 3.6m and the ESO-NTT, in Dec. 1991 we discovered three candidate line_2: sources of Ly-alpha emission associated with a damped Ly-alpha absorber at line_3: z(abs)=2.81, along the line of sight to the quasar Q0528-250. The first two line_4: candidates have been confirmed by spectroscopy. This is the first detection, line_5: confirmed by both imaging and spectroscopy, of a damped Ly-alpha galaxy. The line_6: absorber lies near the quasar z(em)=2.77, and possibly the far side of the line_7: cloud is photoionised by it. In this case we should see the circumference of line_8: the absorber as a ring of Ly-alpha emission. Indeed the nearest of the three line_9: sources may be a section where the ring is bright. However ground-based line_10: observations cannot distinguish between several possible explanations for the line_11: three sources. For example they could be regions of star formation in a single line_12: large (100 kpc) spiral disk, or three galaxies in a compact group. or merging line_13: subunits of a proto-galaxy. High-resolution HST Ly-alpha and continuum images line_14: of this system would greatly clarify these issues, for we would be able to line_15: resolve the three sources, and possibly detect the sought-for ring. Such line_16: detailed information on a young galaxy, proto-galaxy, or cluster, would go a line_17: long way to answering some fundamental questions on the origin of galaxies: line_18: What do galaxies at high redshift z~3 look like\? How large were they, and were line_19: they still being assembled then\? ! ! end of abstract general_form_proposers: lname: MOLLER fname: PALLE inst: 3470 esa: Y ! lname: WARREN fname: STEPHEN mi: J inst: 8058 esa: Y ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: This proposal is only concerned with deep imaging (WFPC2) of one single field. line_2: We shall obtain exposures through the b (F467M), the wide B (F450W), and the line_3: wide I (F814W) filters (10, 3, and 3 hours total exposure time respectively). line_4: These observations should be fairly simple to execute. There are, however, a line_5: few little important details which have to be taken proper into account, so line_6: let me go through them here. line_8: The primary objective of these observations is to go as deep as possible. line_9: Calculating the sky-noise, dark-noise, and read-out-noise from the WFPC2 line_10: handbook, it is seen that in a single orbit the sky-noise is negligible for the line_11: b-images which are hence dominated by read-out-noise with a minor dark-noise line_12: contribution, the sky-noise is equal to the dark-noise for the B-images which line_13: are also read-out-noise dominated but with some sky-noise/dark-noise line_14: contribution, the sky-noise is only just dominating the I images but with a line_15: strong read-out-noise contribution. line_17: 1. To make certain that we obtain the highest possible signal to noise (S/N), it line_18: is therefore important to make all exposures as long as possible. Hence line_19: exposures should be of roughly one orbit length. line_21: 2. If one can believe the sky-levels given in the handbook, only the I images line_22: would benefit from dark time assignment, not the b nor the B images. We would line_23: hence appreciate dark-time for the I images if possible. ! question: 3 section: 2 line_1: line_2: 3. It is important NOT to destroy the good data which have accumulated on the line_3: CCD during the major part of an orbit, by making the exposure too long and line_4: hence possibly add a major sky background in the last few minutes (close to line_5: Earth limb). I don't know if this is a real problem at all, but if it is then line_6: it is an important thing to worry about for this project. Hence, rather cut line_7: a few minutes at each end of the orbit if you are not certain about the sky line_8: level at this point. line_10: 4. Our field contains a fairly bright (V=17.7, B=18.5) quasar only 1.5 arcsec line_11: away from our primary target, as well as many bright (as bright as V=11) line_12: stars. Many of these objects will strongly saturate, and bleed along the line_13: columns. We also expect that many will cause bright diffraction spikes at line_14: angles of 45 deg with respect to the columns. It is important that neither a line_15: bleeding column, nor a diffraction spike will interfere with the extremely line_16: faint objects we are aiming to study. This places some limits on the allowed line_17: position angle, but depending on how we place our objects on the CCDs. The line_18: specifications we have given for the observations below represents one possible line_19: way of combining these constrains. If these specifications are for some reason line_20: impractical to implement, an other combination can be found. line_22: 5. We shall be obtaining a total of twenty 1800 second exposures through the b line_23: filter. Since these will be the less saturated images, we would prefer to have ! question: 3 section: 3 line_1: a set of b images done first, to verify that the pointing and position angle line_2: used do indeed live up to the above requirements. If they do not it could be line_3: unimportant for the b images, but be totally destructive for the I images. ! question: 4 section: 1 line_1: We need the high-resolution of HST to settle the question of the morphology of line_2: the Sources S1, S2, and S3 found in our deep ground based images. Also we need line_3: the small point spread function of HST to be able to get broad band images of line_4: the object of primary interest, S1, which is too close to the quasar to be line_5: observed from ground. line_7: Detailed simulations and S/N calculations have been carried out to calculate line_8: the optimal exposure times in the 3 bands needed to obtain all our goals. line_10: Morphology of the Lyman alpha emission regions. line_11: ----------------------------------------------- line_12: To be able to distinguish between different possible morphologies of the line line_13: emission from S1, we need 10 hours of integration time. Since the b band is not line_14: as narrow as our ground based narrow band filter, we expect that some underlying line_15: continuum may be present in the b image. To subtract the continuum line_16: contribution we shall use a properly scaled B image. Calculating the total noise line_17: in the final combined images from the sky-noise, dark-noise, and line_18: read-out-noise as given in the WFPC2 handbook, we find that subtracting a line_19: scaled 3 hour B image adds about 10% extra noise to the narrow band image, line_20: which is acceptable. A much shorter B exposure would severely degrade the S/N of line_21: the final emission line image. Also, since exposures should not be split, three line_22: hours exposure time will still provide us with sufficient images to be able to line_23: perform an efficient cosmic rejection, which is critical for this programme. ! question: 4 section: 2 line_1: line_2: Equivalent widths of Lyman alpha emission lines. line_3: ------------------------------------------------ line_4: To measure the equivalent width of the emission lines of the three sources, we line_5: also need a high S/N broad band detection of the continuum. For sources S2 and line_6: S3 we have ground based detections of B=26.4. S1 cannot be measured from ground. line_7: Aiming at determining the equivalent widths for sources of B=26.4, and of size line_8: one arc sec square (100 pixels), we shall detect 989 photons in three hours, line_9: with a total rms of 227 e-, hence a 4.4 sigma detection. For the narrow band line_10: image we get a 5.1 sigma detection, and hence the final error on the equivalent line_11: width is fairly evenly distributed between the two but with the major line_12: contribution coming from the B image. To exactly optimise the exposure time in line_13: B to provide smallest error for given total exposure time, B should be a bit line_14: longer than 3 hours. line_16: Broad band morphology and spectral shape of sources. line_17: ---------------------------------------------------- line_18: To reveal the broad band morphology it is most efficient to obtain images in I line_19: where we expect the objects to be brighter, and where the CCDs are most line_20: efficient. Assuming again here an object extending over 1 arc sec square (100 line_21: pixels), and assuming its spectrum to be flat (f-nu = konst, I=25.9), we get a line_22: total detection of 8.1 sigma. This is a slightly better S/N than for both the line_23: b and the B images, and this should give us information about broad band ! question: 4 section: 3 line_1: morphology. When combined with the B image, we obtain the spectral shape of all line_2: three sources. ! question: 5 section: 1 line_1: As argued above (QUESTION: 3), dark time would improve S/N for our I band line_2: images. ! ! !end of general form text general_form_address: lname: Moller fname: Palle category: PI inst: 3470 addr_1: 3700 San Martin Drive city: Baltimore state: MD zip: 21218 country: USA phone: 410 338 1018 telex: moller@stsci.edu ! lname: category: CON ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: PKS0528-250 descr_1: E,314,318,321,322,325 pos_1: RA = 5H 28M 5.16S +/- 0.1S, pos_2: DEC = -25D 5' 44.8" +/- 0.2", equinox: 1950 rv_or_z: Z = 2.811 fluxnum_1: 1 fluxval_1: F-LINE(1216) = 7.4 +/- 0.6 E-17 fluxnum_2: 1 fluxval_2: SIZE = 1 +/- 1 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.000 sequence_1: DEFINE sequence_2: EXPO targname: PKS0528-250 config: WFPC2 opmode: IMAGE aperture: WF3-FIX sp_element: # num_exp: 1 time_per_exp: 1900S priority: 1 param_1: CR-SPLIT=NO req_1: CYCLE 4; req_2: ORIENT 75D +/- 10D; req_3: POS TARG +13.6,+5.7; req_4: SEQ 1.0-4.0 NO GAP ! linenum: 2.000 sequence_1: DEFINE sequence_2: EXPO targname: PKS0528-250 config: WFPC2 opmode: IMAGE aperture: WF3-FIX sp_element: # num_exp: 1 time_per_exp: 2200S priority: 1 param_1: CR-SPLIT=NO req_1: CYCLE 4; req_2: SAME POS FOR 2 AS 1 ! linenum: 3.000 sequence_1: DEFINE sequence_2: EXPO targname: PKS0528-250 config: WFPC2 opmode: IMAGE aperture: WF3-FIX sp_element: # num_exp: 2 time_per_exp: 2200S priority: 1 param_1: CR-SPLIT=NO req_1: CYCLE 4; req_2: POS TARG +13.15,+5.25; req_3: SAME ORIENT FOR 2.0-4.0 AS 1.0 comment_1: THIS FIELD CONTAINS MANY BRIGHT (UP TO comment_2: V=11) STARS. THE CHOSEN ORIENT AND POS comment_3: TARG REPRESENTS ONE POSSIBLE WAY OF comment_4: ADDRESSING THIS. IF THESE SPECS ARE comment_5: HARD TO IMPLEMENT, OTHER ALLOWABLE comment_6: SPECIFICATIONS CAN BE FOUND. ! linenum: 4.000 sequence_1: DEFINE sequence_2: EXPO targname: PKS0528-250 config: WFPC2 opmode: IMAGE aperture: WF3-FIX sp_element: # num_exp: 2 time_per_exp: 2200S priority: 1 param_1: CR-SPLIT=NO req_1: CYCLE 4; req_2: POS TARG +13.15,+5.7 comment_1: THIS FIELD CONTAINS MANY BRIGHT (UP TO comment_2: V=11) STARS. THE CHOSEN ORIENT AND POS comment_3: TARG REPRESENTS ONE POSSIBLE WAY OF comment_4: ADDRESSING THIS. IF THESE SPECS ARE comment_5: HARD TO IMPLEMENT, OTHER ALLOWABLE comment_6: SPECIFICATIONS CAN BE FOUND. ! linenum: 10.000 sequence_1: USE sequence_2: EXPO sp_element: F467M ! linenum: 20.000 sequence_1: USE sequence_2: EXPO sp_element: F467M ! linenum: 30.000 sequence_1: USE sequence_2: EXPO sp_element: F467M ! linenum: 40.000 sequence_1: USE sequence_2: EXPO sp_element: F450W ! linenum: 50.000 sequence_1: USE sequence_2: EXPO sp_element: F814W ! ! end of exposure logsheet ! No scan data records found