Title Spectral line survey in high-z molecular absorption systems Pi T. Wiklind Time 240.3 hrs 1. Name of program and authors Spectral line survey in high-z molecular absorption systems Wiklind T., Combes F. 2. One short paragraph with science goal(s) Molecular line absorption in front of a radio continuum source is a very powerful technique to detect even small quantities of interstellar molecules in external galaxies. It is also complementary to the emission technique: it samples molecules in low excitation state, that would never have been detected in emission. For galaxies at large distances, molecular absorption lines offer the only way to observe rare molecular species. This has been proven through the detection of many molecular species (about 20) at redshifts z=0.25-0.89, using pre-ALMA instrumentation. The sensitivity is largely determined by the strength of the background continuum source, meaning that a large collecting area is the main issue (the sources themselves remain point sources even at high angular resolution). The completion of ALMA makes it possible to make a spectral line survey to an unprecedented level of the molecular interstellar medium in distant galaxies. We propose to carry on a complete molecular line survey (using the available frequency bands) towards 3 remarkable sources at different redshifts, in order to probe the interstellar chemistry and its evolution. Many different molecular species, such as CCH, C3H2, HOC+, SiC, deuterated species etc. are expected to be detected. A complete spectral line survey will allow a detailed comparison of the interstellar chemistry of these three distant sources with that of the Milky Way ISM. In addition, the survey will include several molecular lines which for Milky Way gas are not possible to observe from the ground; such as the ground transition of LiH and water vapor, as well as the elusive molecular oxygen. Noise rms limits have been chosen such that over most of the available frequencies, absorption lines with depth of <1% of the continuum flux can be detected at 5sigma. Over some frequency intervals and for the stronger sources, this limit can be set as low as 0.15% (while lowering the velocity resolution), without excessive exposure times. This corresponds to column densities of CO and HCO+ of 910E12 and 1E10, respectively. It is possible that the density of lines will be large, possibly limiting the detections of individual lines through confusion over certain frequency intervals. We propose to do a systematic survey in the 7 priority bands Band 3: 86 GHz - 116 GHz Band 4: 125 GHz - 163 GHz Band 5: 163 GHz - 211 GHz (6 antennas) Band 6: 211 GHz - 275 GHz Band 7: 275 GHz - 370 GHz Band 8: 385 GHz - 500 GHz Band 9: 602 GHz - 720 GHz for 3 absorption systems already observed with IRAM and SEST, and visible from Chajnantor: PKS1830-211 (z=0.89) PKS1413+135 (z=0.25) CenA (z=0) 3. Number of sources (e.g., 1 deep field of 4'x4', 50 YSO's, 300 T Tauri stars with disks, ...; do NOT list individual sources or your "pet object", except in special cases like LMC, Cen A, HDFS) 3 sources PKS1830-211, PKS1413+135 and CenA (note that PKS1830-211 gives two sight lines through the intervening galaxy, separated by ~6 kpc). 4. Coordinates: 4.1. Rough RA and DEC (e.g., 30 sources in Taurus, 30 in Oph, 20 in Cha, 30 in Lupus) Indicate if there is significant clustering in a particular RA/DEC range (e.g., if objects in one particular RA range take 90% of the time) 1830-211, 1413+135, 1325-43 4.2. Moving target: yes/no (e.g. comet, planet, ...) No 4.3. Time critical: yes/no (e.g. SN, GRB, ...) No 4.4. Scheduling constraints: (optional) No 5. Spatial scales: 5.1. Angular resolution (arcsec): 1 arcsec 5.2. Range of spatial scales/FOV (arcsec): (optional: indicate whether single-field, small mosaic, wide-field mosaic...) 5.3. Required pointing accuracy: (arcsec) 2-5" (depending on frequency) 6. Observational setup 6.1. Single dish total power data: no/beneficial/required NO Observing modes for single dish total power: (e.g., nutator switch; frequency switch; position switch; on-the-fly mapping; and combinations of the above) Nutator 6.2. Stand-alone ACA: no/beneficial/required No 6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: no/beneficial/required No 6.4. Subarrays of 12m baseline-ALMA antennas: yes/no No 7. Frequencies: ALL 7.1. Receiver band: Band 3, 4, 5, 6, 7, 8, or 9 ALL 7.2. Lines and Frequencies (GHz): (approximate; do _not_ go into detail of correlator set-up but indicate whether multi-line or single line; apply redshift correction yourself; for multi-line observations in a single band requiring different frequency settings, indicate e.g. "3 frequency settings in Band 7" without specifying each frequency (or give dummies: 340., 350., 360. GHz). For projects of high-z sources with a range of redshifts, specify, e.g., "6 frequency settings in Band 3". Apply redshift correction yourself.) This is a line survey. We will cover the entire extent of each band falling within atmospheric windows of sufficient transparency. 7.3. Spectral resolution (km/s): 1-4 km/s 7.4. Bandwidth or spectral coverage (km/s or GHz): Band 3: bandwidth 2 GHz Band 4: bandwidth 2 GHz Band 5: bandwidth 1 GHz (6 antennas) Band 6: bandwidth 1 GHz Band 7: bandwidth 0.5 GHz Bnad 8: bandwidth 0.5 GHz Band 9: bandwidth 0.5 GHz 8. Continuum flux density: Fluxes at 90GHz. The continuum flux at higher frequencies is estimated assuming a spectral index of 0.7: S_nu = S_90 * (\nu/90)^-0.7 PKS1413: S_90 = 0.2 Jy PKS1830: S_90 = 2,0 Jy Cen A : S_90 = 6.0 Jy 8.1. Typical value (Jy): PKS1413 PKS1830 Cen A Band 3 0.20 2.00 6.00 Band 4 0.15 1.47 4.40 Band 5 0.12 1.20 3.60 Band 6 0.10 1.00 2.99 Band 7 0.08 0.82 2.46 Band 8 0.07 0.66 1.97 Band 9 0.05 0.50 1.49 (take average value of set of objects) (optional: provide range of fluxes for set of objects) 8.2. Required continuum rms (Jy or K): The limitation to the S/N is defined as the channel noise rms required to detect an absorption line of a given depth. The depth is defined as percentage of the continuum flux density. The ultimate aim is to detect absorptions line at 1% of the continuum level at 5 sigma. For one source (PKS1413) lines are narrow and the required velocity resolution is 1 km/s. 8.3. Dynamic range within image: (from 7.1 and 7.2, but also indicate whether, e.g., weak objects next to bright objects) No imaging 8.4. Calibration requirements: absolute ( 1-3% / 5% / 10% / n/a ) repeatability ( 1-3% / 5% / 10% / n/a ) relative ( 1-3% / 5% / 10% / n/a ) 9. Line intensity: 9.1. Typical value (K or Jy): See 8.2 (take average value of set of objects) (optional: provide range of values for set of objects) 9.2. Required rms per channel (K or Jy): See 8.2 9.3. Spectral dynamic range: 100-500 9.4. Calibration requirements: absolute ( 1-3% / 5% / 10% / n/a ) 5% repeatability ( 1-3% / 5% / 10% / n/a ) 5% relative ( 1-3% / 5% / 10% / n/a ) 1-3% 10. Polarization: yes/no (optional) No 10.1. Required Stokes parameters: 10.2. Total polarized flux density (Jy): 10.3. Required polarization rms and/or dynamic range: 10.4. Polarization fidelity: 10.5. Required calibration accuracy: 11. Integration time for each observing mode/receiver setting (hr): The integration times have been calculated using the actual line flux density (from the ALMA integration time estimator), the required absorption line depth (1-10%), velocity resolution (1-5 km/s) and S/N ratio (3-5). This is calculated for each tuning and then summed for each band and source. Some bands contain atmospheric lines which will increase the system temperature. We have excised those regions which increase the integeation times by a factor more than 2 compared to other regions of the same band. The final observation will have a sensitivity of 1% at 5 sigma for 1 kms/s for approximately 80% of the complete frequency coverage. The remaining 20% have a lower sigma (3) and/or lower line sensitivity (5%) and/or lower velocity resoltuion (up to 5 km/s). A remaining uncertainty in the exposure time estimate is the available correlator configurations. This defines the number of tunings needed to cover a given band. We have assumed conservative bandwidths (see 7.4). Also, time for tuning is not included in the time estimate. PKS1413 PKS1830 Cen A Band 3 6.0 1.5 1.0 Band 4 14.4 3.6 1.0 Band 5 -- 6.3 8.0 Band 6 19.2 10.8 5.9 Band 7 42.8 3.8 16.2 Band 8 36.0 9.7 8.7 Band 9 -- 28.2 17.2 Total 118.4 63.9 58.0 12. Total integration time for program (hr): 240.3 + overhead 13. Comments on observing strategy : (optional) (e.g. line surveys, Target of Opportunity, Sun, ...): This is a molecular line line survey. The observations are self-calibrated using the central continuum source. The pointing accuracy needs to be than 5". Very good weather conditions are only required for high frequency observations. A homogeneous sensitivity is necessary in order to allow a comparative abundances study of weak lines. The estimated time can be decreased by lowering the target sensitivity or only choosing PKS1830-211 and Cen A as targets. However, given the uniqueness of this data set, we would prompt for a significant time allocation. -------------------------------------------------- Review v2.0: quasarexgal_1 = 1.3.1 Spectral line survey in high-z molecular absorption systems Wiklind T., Combes F. Very interesting project. Could it in fact be carried out at _any_ angular resolution? This would make it quite flexibly scheduled - more of an operational question than anything having to do with science.