AUSAC Meeting · March 9 & 10, 2009 Chris Salter (NAIC – Arecibo) G A L F A.
-
Upload
bennett-parrish -
Category
Documents
-
view
217 -
download
2
Transcript of AUSAC Meeting · March 9 & 10, 2009 Chris Salter (NAIC – Arecibo) G A L F A.
AUSAC Meeting · March 9 & 10, 2009
Chris Salter (NAIC – Arecibo)
G A L F A
AUSAC Meeting · March 9 & 10, 2009
GALFA Survey Family
• H I Line (GALFA-H I)
• Continuum (GALFA-CON = GALFACTS)
• Radio Recombination Lines (GALFA-RRL)
• Each GALFA sub-consortium has its own membership and internal organization.
• All GALFA data will be made public through the National Virtual Observatory.
AUSAC Meeting · March 9 & 10, 2009
RRL Plane Survey• Galactic Structure• Chemical Abundances• Warm Diffuse ISM
• Survey |b| < 5o, 2000 h• 300s int; co-add lines• Start June, PALFA/ZOA
Terzian et al.
a2064 PI: Yervant Terzian
AUSAC Meeting · March 9 & 10, 2009
RRL -Lines in 300 MHz ALFA Bandpass
AUSAC Meeting · March 9 & 10, 2009
RRL Observing Strategy
• Commensal with PALFA + ZOA• Share 300 MHz pDev spectrum with ZOA; 5 km/s
channels (H + He lines; narrower C in followup)• Observe 12 -lines in band & combine for S/N• 4.6min/pointing; 3 points at same (AZ, ZA) for
ON-OFF comparison (RA sep: 1.15o cos )• Sparse PALFA pointing grid (figure); fill in later• PALFA has already done most of |b| < 1o sparsely;
do 2nd pass on wider alt. grid points for RRL/ZOA
AUSAC Meeting · March 9 & 10, 2009
RRL (PALFA) Pointing Grid
• 5min/point• sparse grid;
fill in later• ½ S/N in
white points• each color
observed on different night; OFF pos on same
P. Freire
AUSAC Meeting · March 9 & 10, 2009
The G-ALFA Continuum Transit Survey (GALFACTS)
• Spectropolarimetric survey of entire Arecibo Sky (-0.8o < < +37.8o = 12,734 deg2 in 1500 h)
• 8192 channels over a bandwidth of 300 MHz for RM coverage and RFI excision (spectrometer being built)
• 500 μJy ~ 5σ polarized flux sensitivity• fast meridian scanning : 2 degrees / min• awaiting pDev data translation software, airport
radar RFI solution (signal path filter or other fix)• PI: Russ Taylor (www.ras.ucalgary.ca/GALFACTS)
AUSAC Meeting · March 9 & 10, 2009
Mapping Technique: ZA Nodding + AZ Wagging
ALFA beams
Tracks after several passes
These are woven together to form a map.
AUSAC Meeting · March 9 & 10, 2009
Full Stokes Multibeam CLEAN
S. GuramMSc ThesisU. Calgary
Stokes IDirty Image
MultibeamClean Image
NVSSComparison(1/4 beam)
AUSAC Meeting · March 9 & 10, 2009
Perseus ISM: Polarized Intensity
Taylor, Salter, et al.
AUSAC Meeting · March 9 & 10, 2009
Magnetic Fields from Polarimetry• A foreground magnetized plasma changes the polarization position angle of background polarized emission via Faraday Rotation:
where the Rotation Measure is given by
PSR B1154-62 (Gaensler et al 1998)
20 RM
dlBn ||e ]Gcmpcm [rad 81.0RM -13-1-2
backgroundsynchrotronemission
observer
Faraday screen C. Bredeson
(from diffuse or compact source)
AUSAC Meeting · March 9 & 10, 2009
Global Galactic B-Field Structure• Faraday Rotation Measures toward
point sources• Pathfinder project for SKA ``origin
and evolution of cosmic magnetism’’ initiative (GALFA can probe ~104 sightlines; SKA will get ~107)
• Milky Way – thorough sampling of arm pattern in plane and at higher latitudes, where role of field is largely unknown
• Nearby Galaxies – map global field, determine open vs. closed geometry
M51 (Fletcher & Beck 2004)
Milky Way (J. Brown)
AUSAC Meeting · March 9 & 10, 2009
ISM Magnetic Field Structure
• Diffuse Faraday Screens
• Turbulence + Power Spectra
• Discrete Objects
– SNRs
– HII Regions
– Molecular Clouds & PDRsHaverkorn et al. (2003)
Gaensler et al. (2001)
A. R. Taylor
AUSAC Meeting · March 9 & 10, 2009
Polarized Cosmic Background • Planck requires low-frequency
constraints on Galactic synchrotron foreground to measure polarized cosmic background correctly. High frequency resolution is needed to unwrap and remove Faraday rotations in the foreground for an accurate polarization measurement.
• Planck will provide dust polarization maps to compare with ISM B-field radio data. These trace orthogonal field components and are thus highly complementary.
COBE
Planck
AUSAC Meeting · March 9 & 10, 2009
GALFACTS Precursor vs. Effelsberg
Stokes Q
Stokes IALFA beam0
Effelsberg
ALFA beam0
Rotation Measure:
RM = dPA / 2
Position Angle:
PA = 0.5 * atan (U/Q)
Effelsberg
AUSAC Meeting · March 9 & 10, 2009
Multi- wavelengthportrait of thePerseusMolecularCloudregion.
~1% of the GALFACTS+ TOGS2 survey area!
Knee et al.
Taylor et al.
AUSAC Meeting · March 9 & 10, 2009
Arecibo Sky Coverage(i.e. GALFACTS/TOGS2 Area)
I-GALFA
AUSAC Meeting · March 9 & 10, 2009
CGPSVGPS
SGPS
I-GALFA Plane H I Survey
10 x IGPS sensitivity, 4 x velocity resolution
I-GALFA Survey: 2008-9
AUSAC Meeting · March 9 & 10, 2009
GALSPECT Pointing Record as of 2008 March 14
GALSPECT has 8192 channels over 7.14 MHz => 0.18 km/s per channel, +/- 750 km/s coverage
GALFA H I Observations
AUSAC Meeting · March 9 & 10, 2009
GALFA H I Projects
a2186/2144/2390
a2048/2059a2010/2059 a2130/2124
a2056/2051a2060
a2055
a2034
a1943
a2004
a2174/2294
a2221
ALFALFA/TOGS1 AGES/TOGS1 GALFACTS/TOGS2
IGALFA/ZOA/ GALFACTS2 DISK-
HALOMBW/ZOA
PERSEUS
TAURUS
HALOCLOUDS
WINGS
a2220
a2222a2187
a2050
a2011 a2011a2172
a2172
a2147a2032
TIP MAGSTREAM
GEM OB1
TRUE FIL
SHELL
HIGH-LAT CLOUDS
HIGH-LATTURBULENCE
WATER FALL
OUTER HALO
PRECURSOR
COLDCLOUD
(78%)
(56%) (16%)
(start May 3)
(start ASAP)
(Trms ~ 0.25 K)
(Trms ~ 0.15 K) (Trms ~ 0.04 K) (Trms ~ 0.35 K)
AUSAC Meeting · March 9 & 10, 2009
GALFA H I : 8.5o Atlas Tile Cubes
Width = 512 pixels * 1.0' = 8.53o = 152.84 * 3.35' beam; 32’ overlaps4 bytes/pix * 8192 chan = 8 GB/tile cube; grid of 45 x 5 tiles = 1.8 TB(prelim: 2 bytes/pix * 2048 chan = 1 GB/tile cube * 2 (narrow & wide)
AUSAC Meeting · March 9 & 10, 2009
TOGS H I (in progress)
Right Ascension
Dec
lin
atio
n
Fall Data from 2005 + 2006
AUSAC Meeting · March 9 & 10, 2009
IRAS 100m dust emission
Right Ascension
Dec
lin
atio
n
Similar structure as HI!
AUSAC Meeting · March 9 & 10, 2009
MBM 53-55 H I “Shell”IRIS Dust + CO Contours GALFA HI + Velocity Colors
HI gives IRAS velocities; study HI-H2 transition (Gibson et al.)
AUSAC Meeting · March 9 & 10, 2009
TOGS H I (in progress)
Right AscensionDec
lin
atio
n
Spring Data from 2005 + 2006
AUSAC Meeting · March 9 & 10, 2009
Leo Cold Cloud: GALFA HI image of an extremely cold (17 K) and nearby (< 40 pc) CNM cloud in our Galaxy's ISM (Meyer et al. 2006). Color rep-resents LSR velocity and bright-ness 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 UV stellar absorption is underway. This work is to be published by J. E. G. Peek et al.
AUSAC Meeting · March 9 & 10, 2009
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 is to be published by J. E. G. Peek et al.
AUSAC Meeting · March 9 & 10, 2009
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 is to be published by J. Peek et al. and J. Grcevich et al.
AUSAC Meeting · March 9 & 10, 2009
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 is to be published by S. Stanimirovic et al.
AUSAC Meeting · March 9 & 10, 2009
M33: Optical Photo by David Malin (Isaac Newton Telescope, IAC/RGO)
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 is to be published by M. E. Putman et al.
AUSAC Meeting · March 9 & 10, 2009
GALFA Summary
• 3 Sub-Consortia (H I, CON, RRL)• Small GALFA-H I projects done. TOGS1 in
progress; initial data cubes made; I-GALFA/ GALFACTS start in May.
• GALFA-RRL/ZOA/PALFA start in June• Main GALFACTS start ASAP• All final GALFA datasets will be on NVO.• GALFA website: www.naic.edu/alfa/galfa
AUSAC Meeting · March 9 & 10, 2009
End
AUSAC Meeting · March 9 & 10, 2009
GALFA - H I Projects
56% Mar 1716% Mar 1778% Mar 17
start ASAP
start May 3
AUSAC Meeting · March 9 & 10, 2009
Data products will be made public through the NVO.
GALFACTS Data Pipeline
AUSAC Meeting · March 9 & 10, 2009
Polarized Continuum Intensity: DRAO ST + Effelsberg 100m + DRAO 26m
This is ``Faraday screen’’ structure in the Magneto-Ionic Medium.
K
R. Kothes
GALFA-CON
AUSAC Meeting · March 9 & 10, 2009
AUSAC Meeting · March 9 & 10, 2009
AUSAC Meeting · March 9 & 10, 2009
AUSAC Meeting · March 9 & 10, 2009
AUSAC Meeting · March 9 & 10, 2009
GALFA-H I – E Pluribus Unum
[Josh Peek]
AUSAC Meeting · March 9 & 10, 2009
Fine Structure in Perseus H I
Lewis Knee et al.
AUSAC Meeting · March 9 & 10, 2009
Fine Structure in Perseus H I
Lewis Knee et al.
AUSAC Meeting · March 9 & 10, 2009
Fine Structure in Perseus H I
Lewis Knee et al.
AUSAC Meeting · March 9 & 10, 2009
High-Velocity Clouds in the Galactic Halo
Josh Peek
AUSAC Meeting · March 9 & 10, 2009
Forbidden-Velocity Line Wings in the Galactic Disk
Bon-Chul Koo
AUSAC Meeting · March 9 & 10, 2009
Narrow-Line H I Absorption and Molecular Clouds
MarkoKrco
AUSAC Meeting · March 9 & 10, 2009
Stuff to Talk About
• GALFA Survey Groups (HI, CON, RRL)• Status of Survey Projects
– HI• TOGS• Disk-Halo & other completed projects• I-GALFA
– CON• GALFACTS Main + I-GALFA commensal (radar RFI)
– RRL : PALFA/ZOA commensal (PDEV)
• Science Results, Presentations, & Publications
AUSAC Meeting · March 9 & 10, 2009
New Images to Show
• Partial Lambda & turnaround stuff?• GALFACTS newsletter figs – multibeam clean, Per map• RRL figure Yervant emailed in Dec/Jan?• TOGS tile layout and specifications• TOGS fall and spring local & HVC maps• TOGS poster images
– Magellanic streamlets– M33– Leo Cloud– MBM 53-55
• blah
AUSAC Meeting · March 9 & 10, 2009
Other RRL Figures
• Sample 4’ continuum map of survey area? (indicate sensitivity if possible; whitepaper says H line in sources down to 0.5 Jy, but is this for actual PALFA survey this summer? Not clear – whitepaper says 300s in one place and 20m in another!)
• Arecibo RRL Spectra (RRL whitepaper Figure 4, from 1978?? Is this useful?)
• PALFA pointing grid with description of visit & ON-OFF strategy (RRL whitepaper Figure 9)
• Note somewhere that high-res C obs will be followup rather than part of main survey