Arecibo Observatory Bandpass Corrections for the Star-Forming Region W51

1. Arecibo Observatory Bandpass Corrections for the Star-Forming Region W51 Principal investigator: Amilcar Torres (UPR-RP) Co-Investigators: Fernando Aponte (UPR-RP), Emy Rivera (UPR-RP) Advisors: Dr. Mayra Lebron (UPR-RP), Dr. TapasiGhosh (Arecibo Observatory), Dr. Chris Salter (Arecibo Observatory), Dr. Hector Arce (Yale University), Dr. Robert Minchin (Arecibo Observatory).

2. Outline • Introduction • Terminology • Methodology • Data Collection • Instruments • Frequency’s and Dates Observed • DPS Analysis • Technical Details • Instruments • Reduction • Data Quality before DPS analysis • DPS Test • Conclusion • Current Work • Future Observations • Future Analysis

3. Introduction • The Arecibo Galactic Chemical Survey • To truly understand the connection between life and space, a wide study about the chemical inventory of the star formation region is needed. Detecting and identifying the complex molecules within the diverse environments of the Interstellar Medium (ISM) is essential for understanding their possible formation.

4. Introduction • Studies done on different areas (other than W51) have revealed a diverse spectrum that is rich in molecular transitions. These molecules are characterized as “pre-biotic’’ and are essential in creating more complex molecules. Hence, getting more observations done of different areas, in this case W51 is essential in understanding the presence and development of different molecules that might have a connection with the development of life.

5. Introduction • However, it is also necessary to observe W51 in order to correctly catalogue the spectral lines that are observed in the region.

6. Terminology • Outline • Frequency • Bandpass • Interstellar Medium (ISM) • Mock Spectrometer • Spectral line • Splatalogue • Polarization • Position Switching • Double Position Switching

7. Terminology • Frequency: • The number of cycles or completed alternations per unit time of a wave or oscillation. • Bandpass: • A device that passes frequencies within a certain range and rejects (attenuates) frequencies outside that range. • Interstellar Medium (ISM): • Matter that exists in the space between the star systems in a galaxy, mostly gas in different states.

8. Terminology • Mock Spectrometer: • The spectrometer used to observe W51. A spectrometer is defined as, “an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum.” [17] The Mock spectrometer has fourteen boards, each of these boards subdivides the frequency into smaller parts. Therefore, this makes it easier to analyze the data because scientists get to study smaller packets of the frequency instead of a whole.

9. Terminology

10. Terminology • Spectral Line: • “A line in a spectrum due to the absorption or emission of light at a discrete frequency.” [5]

11. Terminology • Splatalogue: • An online website that catalogue’s all of the known spectral lines. This gives scientists a great database in which they can identify the spectral lines which have been found in the data that they’re analyzing.

12. Terminology • Polarization: • “A state, in which rays of light or similar radiation exhibit different properties in different directions.” [4]

13. Terminology • Position Switching : • The process of collecting data on and off the source. Bon • Plot: Position Switching Boff

14. Terminology • Double Position Switching: • Is the process of collecting data on and off an observation source in addition to collecting data on a nearby calibrating source. In the case of W51, there is no brighter region than the latter. Therefore, the use of a lower intensity calibrating source is necessary. Nonetheless, this does not affect the end result of correcting the ripples obtained in the frequency observed.

15. Methodology • A. Data Collection • Instruments • Arecibo Observatory (AO). • Wideband Mock: • provides 5.2 kHz wide channels over a 1 GHz bandwidth. • C-band Receiver • Frequency’s and Dates Observed • Date Observed • June 3, 2010 • June 4,2010 • Frequency Range: • 4503MHz-5034MHz

20. Methodology • B. Double Position Switching (DPS) Analysis • Reduction • Data Quality before the DPS test. • Line identification: • After a line has been detected on a graph of its respective scan, identification of the spectral lines frequency is required in order to catalogue it. • Inside Splatalogue, the frequency of the spectral line is typed in the search function which provides known complex molecules and their respective spectral lines. This allows the correct identification of the spectral line in question. 5008.5206MHz H(109)α H(196)δ 5004.7586MHz H(137) β 5010.5948MHz He(109)α

21. Methodology • Technical problems on the data: • In some cases the Radio Telescope (AO) had lost sight of the source. • This is shown in the spectral graph. It is observed at a certain space in which the frequency shows an erroneous collection of data. • Another source of error is Mock damage. This is represented by and erroneous frequency on the midpoint of the graph.

22. Methodology • Radio Frequency Interference: • Radio Frequency Interference is identified when a specific position switching graph yielded the following: • A spectral line is observed in only one of the polarizations. • After identifying a possible spectral line and searching for the frequency in splatalogue, it does not turn back a result for the specified frequency. This indicates a clear interference.

23. Double Position Switching Position Switching 5008.5206MHz H(109)α H(196)δ 5008.5206MHz H(109)α H(196)δ 5004.7586MHz H(137) β 5004.7586MHz H(137) β 5010.5948MHz He(109)α 5010.5948MHz He(109)α Methodology

24. Conclusion • A. Current Work • Graph interpretation • Current data discards the necessity of utilizing multiple bandpasses. Therefore, more time can be spent analyzing the observation source. • B. Future Observations • Continue DPS data reduction on the observations obtained at different dates throughout summer 2010. • Complete data calibration. • Identification of spectral lines. • Spectral line Analysis. • Report the results.

25. Conclusion • C. Future Observations (Project) • There will be future observations during the summer of 2011 and 2012. • Build a molecular line catalog of the source. • Find undetected complex interstellar medium molecules.

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