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The GALFA-HI Survey starting with TOGS

Mapping Hydrogen in the Galaxy, Galactic Halo and Local Group with the Galactic Arecibo L-Band Feed Array (GALFA).

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The GALFA-HI Survey starting with TOGS

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  1. Mapping Hydrogen in the Galaxy, Galactic Halo and Local Group with the Galactic Arecibo L-Band Feed Array (GALFA) The GALFA-HI Survey will map the entire Arecibo sky (shown between the red lines in Figure 1) at 21-cm over a velocity range of -700 to +700 km/s with a resolution of 0.2 km/s and 3.4’ using the Arecibo L-Band Feed Array. This poster presents highlights from the TOGS (Turn on GALFA Survey) portion of GALFA-HI which covers the largest portion of the Arecibo sky with commensal drift scan observing (blue boxes in Figure 1). A peak brightness temperature map and channel map showing the sky mapped thus far are shown in Figure 2. The sharp contrast between previous HI maps and GALFA’s is shown in Figure 3. More information can be found at http://www.astro.lsa.umich.edu/~mputman/togs.html and http://www.naic.edu/alfa/galfa. Figure 1: The LAB HI survey (0.6 deg resolution; Kalberla et al. 2005) with the area covered by the GALFA-HI Survey shown between the red lines and the area covered by TOGS in the blue boxes. Figure 2: Top: Peak brightness temperature map of the sky mapped thus far by TOGS in the Fall. Bottom: Channel map at 3 km/s showing the area of sky mapped thus far by TOGS in the Spring. Figure 3: Comparing LAB Survey data (left; 0.6 deg beam) to GALFA data (right; 3.4’ beam). The GALFA-HI Survey starting with TOGS M.E. Putman (U. Michigan), K. Douglas (SSL, Berkeley), S.J. Gibson (NAIC), C. Heiles (UC-Berkeley), E. Korpela (SSL, Berkeley), J.E.G. Peek (UC-Berkeley), S. Stanimirovic (UW-Madison) Galactic Shells: GALFA peak brightness temperature HI map (left) and IRIS 100 micron thermal dust emission (right) from the nearby molecular cloud complex MBM 53-55 (e.g., Yamamoto et al. 2003), which is thought to be part of an expanding shell (Chastain et al. 2006). The rich detail provided by GALFA enable direct comparisons between the datasets and provide information on the HI content, environment and kinematics of the shell. This work to be published by S.J. Gibson et al. Very High-Velocity Clouds (VHVCs): GALFA reveals the detailed structure of VHVCs in the halo and can be used to probe the diffuse halo medium through fingers extending off the sides of the cloud and head-tail clouds (e.g. Peek et al. 2007; Stanimirovic et al. 2006). This work to be published by J. Peek et al. and J. Grcevich et al. Needles: This image shows bundles of very fine (~5’) filamentary features at high galactic latitude (b > 80). These features, discovered by GALFA, are highly correlated to starlight polarization(red lines), indicating magnetic fields along their length. In addition, the angle of both the magnetic fields and the filament bundles is coincident with the angle of the local spiral arm. We find these 'filament bundles' throughout the diffuse ISM, indicating a new technique for finding the orientation of magnetic fields. This work to be published by J. Peek et al. Leo Cold Cloud: To the right is a GALFA image of an extremely cold (17 K) and nearby (< 40 pc) CNM cloud in our Galaxy's ISM (Meyer et al. 2006). Color represents LSR velocity and brightness represents hydrogen column density. Because of its location within the local hot bubble, this cloud makes a very interesting laboratory for the study of the CNM and the CNM/HIM interface. A program comparing the 21-cm observations to infrared dust emission and optical and ultraviolet stellar absorption is underway. This work to be published by J. Peek et al. lll lll Magellanic Stream: The HI velocity field of the Magellanic System from the Parkes telescope (left; 15.5’ resolution; Putman et al. 2003) and the tip of the Magellanic Stream as observed by GALFA (right). The GALFA data reveal four coherent 10-15 degree long filaments that differ in morphology and velocity structure and may have different origins/ages. Numerous small clouds with high negative velocities are also evident. Some of these clouds show evidence for a multiphase medium and may result from spatial fragmentation of the Stream due to thermal instability. This work to be published by S. Stanimirovic et al. M33: A Local Group galaxy as revealed by GALFA. What was traditionally thought to be a quiescent galaxy shows clear evidence for either tidal/ram pressure disruption and/or gas cloud accretion. This work will be published by M. Putman et al.

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