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Proposal Identification No.:

A2985 Arecibo Observatory

Date Received: 2015-Feb-25 17:50:55 William E. Gordon Telescope Observing Time Request COVER SHEET

Section I - General Information
Submitted for Mar 1 2015. 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 36.5

less than 100 GB

"Dark" Atomic Gas in the Diffuse Interstellar Medium

Far-infrared and gamma-ray surveys indicate there are significantly more nucleons in the diffuse interstellar medium than are traced by HI and CO emission. This proposal tests one hypothesis for the supposed "dark gas" associated with the far-infrared and gamma rays. Cold HI is optically thick and does not emit as readily in the 21-cm line, but it can be seen in absorption against radio continuum sources. We will observe radio sources near clouds with far-infrared emission measured by Planck to be in excess of the high-resolution HI observations from the Arecibo GALFA HI survey. We will also test another hypothesis that the "dark gas" is molecular by observing OH absorption toward the brightest sources. Outreach Abstract: The space between stars is filled with a clouds similar to the sky above us having clouds in the Earth's atmosphere. The interstellar clouds can be seen with radio and infrared telescopes and they contain the material from which stars form. The focus of this Arecibo pro ject is to measure the composition of the clouds and the total amount of material in the small clouds that are most typical. These clouds combine to form the giant clouds where clusters of stars form. To understand the life cycle of the material that goes into star formation, we need to know what is the composition and mass of the clouds. Space measurements by the European Planck microwave telescope and the NASA Fermi gamma-ray telescope showed the interstellar clouds are twice as massive as we thought, but what is all this extra material that seems "dark" to our previous measurements?

Name William T Reach Carl Heiles

Institution USRA/SOFIA Astronomy Department, U.C. Berkeley

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

Phone 650-919-4705 510-642-4510

Student no no

1


This work is not part of a thesis.

Remote Observing Request

Observer will travel to AO Remote Observing X 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 Interval­Interval 22:00 ­ 01:30 07:30 ­ 10:30 ­ ­

Days Needed at This Interval 7 4

Time Constraints (Must Be Justified in the Prop osal Text)

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

Sp ecial Equipment or setup:

none

Section IV - RFI Considerations Frequency Ranges Planned
1420.4 1665.4 1667.4 2


Section V - Observing List Target List
CLOUD RA DEC RISE SET G94-36 23:05:23 +20:59 21:43 00:29 G95-51 23:43:14 +08:58 22:43 00:55 G104-39 23:58:42 +21:50 22:36 01:22 G108-53 00:17:06 +09:45 23:04 01:31 G138-52 01:29:26 +10:10 00:16 02:44 G198+32 08:27:26 +26:12 07:10 09:46 G221+35 09:08:42 +09:26 07:57 10:21 G236+39 09:45:58 +00:35 09:12 10:20

3