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Proposal Identification No.:

A2902 Arecibo Observatory

Date Received: 2014-Mar-03 11:54:30 William E. Gordon Telescope Observing Time Request COVER SHEET

Section I - General Information
Submitted for Mar 1 2014. This proposal has not been submitted before. Proposal Type: General Category: Sub-Category: Observation Category: Time Requested this semester: Hours already used for this pro ject: Additional Hours required to complete pro ject: Minimum Useful Time: Expected Data Storage: Prop osal Title: ABSTRACT: Regular Astronomy Spectroscopy Galactic 84 0 1 hour less than 100 GB

Dark Molecular Gas in the Diffuse Interstellar Medium

Far-infrared and gamma-ray all-sky surveys show evidence for extensive 'dark gas' in the diffuse interstellar medium not traced by 21-cm HI or 3-mm CO lines. We found that the dust column density measured by Planck at 5 arcmin scales follows the HI column density measured by Arecibo with its 3 arcmin beam in the 21-cm line, except with different infrared/HI slopes in different regions. The differences between regions could be their different molecular gas content. We propose to observe the OH emission from a diffuse high-latitude cloud that has evidence for 'dark gas' in the Planck/Arecibo comparison. If the column density of molecular gas found in this experiment matches the apparent excess in the dust column density, then we can calibrate and use the Planck excess to image the diffuse molecular gas. Outreach Abstract: The space between the stars is filled with diffuse clouds of dust and gas. Those clouds for stars when they are dense enough, and the stars return material to the interstellar clouds during their lives and at the ends of the lives. The most tenuous clouds are also the largest and some of the longest-lived. The inventory of material in them is not yet complete, because evidence has pointed toward a 'dark gas' component to explain the larger amount of dust emission and gamma-ray scattering than one would predict based on the gas known from existing surveys. In this pro ject we study a dust cloud that appears to have 'dark gas' with Arecibo, to detect faint emission from molecular gas. If we confirm that the dark gas is indeed molecules, then we can use the Arecibo and spacecraft data to measure the distribution of dark gas in detail.

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Name William T. Reach Carl Heiles

Institution Universities Space Research Association University of California, Berkeley

E-mail wreach@sofia.usra.edu heiles@astro.berkeley.edu

Phone 650-602-2292 510 280 8099

Student no no

This work is not part of a thesis.

Remote Observing Request

Observer will travel to AO X Remote Observing In Absentia (instructions to operator)

Section I I - Time Request
The following times are in LST. For these observations night-time is not needed.

Begin ­ End Interval ­ Interval 10:24:43­12:36:03 ­ ­ ­

Days Needed at This Interval 40

Time Constraints (Must Be Justified in the Prop osal Text) none

Section I I I - Instruments Needed
L-wide Atmospheric Observation Instruments:

Sp ecial Equipment or setup: We need the interim correlator.

Section IV - RFI Considerations
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Frequency Ranges Planned
1420 1665 1667 1720

Section V - Observing List Target List
G236+39 ra: 11:30 dec: 07:26 rise: 10:24 set: 12:36

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