steven gibson

AUSAC Meeting · March 17&18, 2008

Steven Gibson

G A L F A


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.


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


RRL -Lines in 300 MHz ALFA Bandpass


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


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


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)


Mapping Technique: ZA Nodding + AZ Wagging

ALFA beams

Tracks after several passes

These are woven together to form a map.


Full Stokes Multibeam CLEAN

S. GuramMSc ThesisU. Calgary

Stokes IDirty Image

MultibeamClean Image

NVSSComparison(1/4 beam)


Perseus ISM: Polarized Intensity

Taylor, Salter, et al.


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)


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)


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


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


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


Multi- wavelengthportrait of thePerseusMolecularCloudregion.

~1% of the GALFACTS+ TOGS2 survey area!

Knee et al.

Taylor et al.


Arecibo Sky Coverage(i.e. GALFACTS/TOGS2 Area)

I-GALFA


CGPSVGPS

SGPS

I-GALFA Plane H I Survey

10 x IGPS sensitivity, 4 x velocity resolution

I-GALFA Survey: 2008-9


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


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)


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)


TOGS H I (in progress)

Right Ascension

Dec

lin

atio

n

Fall Data from 2005 + 2006


IRAS 100m dust emission

Right Ascension

Dec

lin

atio

n

Similar structure as HI!


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.)


TOGS H I (in progress)

Right AscensionDec

lin

atio

n

Spring Data from 2005 + 2006


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.


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.


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.


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.


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.


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


End


GALFA - H I Projects

56% Mar 1716% Mar 1778% Mar 17

start ASAP

start May 3


Data products will be made public through the NVO.

GALFACTS Data Pipeline


Polarized Continuum Intensity: DRAO ST + Effelsberg 100m + DRAO 26m

This is ``Faraday screen’’ structure in the Magneto-Ionic Medium.

K

R. Kothes

GALFA-CON


GALFA-H I – E Pluribus Unum

[Josh Peek]


Fine Structure in Perseus H I

Lewis Knee et al.


High-Velocity Clouds in the Galactic Halo

Josh Peek


Forbidden-Velocity Line Wings in the Galactic Disk

Bon-Chul Koo


Narrow-Line H I Absorption and Molecular Clouds

MarkoKrco


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


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


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

steven gibson

Documents

galfa data

galfah icontinuum galfa

global field

role of field

ism bfield radio data

polarized intensitytaylor

polarized flux

o cos dsparse palfa