Extragalactic H2CO Densitometry

To Do

1. Sum all spectra per source and transition (H2COJ1, H2COJ2, H111alpha, OH). During this analysis weed-out all bad spectra (bad lags, poor spectral baselines, etc.) on a per-spectrum basis. (DONE)
2. Boxcar smooth to 20 km/s spectral resolution for all spectra. (DONE)
3. Fit baselines. Use existing CO measurement velocity ranges to assess reality of marginal (and not-so-marginal) H2CO, H111alpha, and OH detections. (DONE)
4. Derive peak, velocity of peak, and FWZI (Full Width Zero Intensity) for each detection. Tabulate information derived. (DONE)
5. For nondetections, derive RMS within post-smoothed baseline region. Tabulate information derived. (DONE)
6. Derive LTE column density (use column density calculation document you read earlier). Do for all measurements, including nondetections. Think about what a good limit would be to use for nondetections.
7. For marginal new H2CO detections investigate existing published information on dense gas emission in each galaxy. Use as justification (or not) for new H2CO detection. Write notes describing research and justification for each.
8. Play with H2CO LVG model. Understand what happens to line temperatures, optical depths, and excitation temperatures as density, kinetic temperature, and column density are changed.

Results

New Detection Notes

• IC 1623: This galaxy had a suckout on its spectra. Until this suckout is fixed, it wil be difficult to determine if there is a signal within the data.
• NGC 1144: Strong absorption of -7.45 at a velocity ~8520 km/s. Gao and Solomon (2000) listed a velocity of ~8750 km/s while NED had ~8650 km/s. Bransford and Appleton (1999) discuss the broad H-alpha, HI and CO emission spreading over a huge velocity range. Tracing the HI in their paper, our H2CO seems to peak in conjunction with a H! peak at the same velocity. A paper published by Appleton, Charmandaris, Gao, Jarrett and Bransford (2002) invetigated neutral hydrogen (HI) of this galaxy merger (Arp 118 consists of NGC 1143 and 1144) and clearly mapped several regions of interaction with varying velocities. They trace gas from ~8200 through ~8850 km/s. Any emission in this velocity range I believe can be accounted for due to these interaction regions.
• NGC1365: I had to do a lot of fannaggling to dig this absorption line out. While the peak emission was at 1476 km/s, there was a second peak around 1582, and the range over which I integrated was centered at almost the velocity quoted by G&S and NED. while weak, I believe this constitutes a solid detection.
• NGC 3227: Another galaxy which is part of a merging system (Arp 94, NGC 3226, NGC 3227). Although not included in the HCN survey but Gao and Solomon, we have detected a strong H2CO emission of 6.89. There is a discrepancy in velocity however, as our peak lies at ~900, and NED quotes the velocity at ~1160. Thus far, I have not been able to find relevant reference to this system in the literature to support our detection.
• UGC 02369: This galaxy suffered from a major suckout of the spectra. I will need to come back to this and very carefully one by one look through spectra and try to find acceptable ones to use. It will be exceedingly difficult to extract a signal without first cleaning this error up.

Notes and Reports

• Extragalactic H2CO Project Results and Discussion: General observation notes and results.