The drift scan survey
with MWA
Shintaro Yoshiura
Kumamoto University
Collaborators : K.Kubota, K,Takahashi, J.Line B.Pindar +Contents• Murchison Wideﬁeld Array!

• Calibration with drift scan data!

• Summary「銀河進化と遠方宇宙」

2017 @ 熊本 アーデンホテル阿蘇 :2 /18 ページ

Murchison Wideﬁeld Array
Precursor of SKA
Main science : detecting 21cm line at EoR
MWA dipole antenna
1 tile has 4×4=16 dipoles

ーチソン・ラジオ＝アストロノミー天文台

Credit : Natasha Hurley-Walker-26.7033, 116.671

画像 ©2016 NASA、TerraMetrics、地図データ ©2016 GBRMPA、Google200 km「銀河進化と遠方宇宙」

2017 @ 熊本 アーデンホテル阿蘇 :3 /18 ページ

the 32 channels in the analog beamformer has an independently controlled 32-step delay using five binary-weighted
delay steps, each of which can be switched in or out. When
any delay step is switched out, a gain-matching circuit stubis switched in to maintain relatively constant gain regardlessof delay setting (tile gains are calibrated post-correlation).
The delay steps are multiples of 435 picoseconds, allowing

Murchison Wideﬁeld Array
Figure 5. A schematic antenna tile layout.

20NEBEN ET AL.: MEASURING MWEWTile conﬁguration

05The MWA: The SKA Precursor at Low Radio Frequencies-10-20-30

Beam shape

Figure 6. MWA tiles and analog beamformers deployed in the field.

Beam former

PASA, 30, e007 (2013)
doi:10.1017/pasa.2012.007

6Tingay et al.
http://journals.cambridge.org

Downloaded: 11 Feb 2015

IP address: 128.250.55.254

UV plane
Figure 2. Plan of the MWA infrastructure, as built at the MRO. The hub referred to in the text is located at (0, −200),with seven radial trench lines shown in red. Receiver locations are marked as red crosses and tile positions are marked
as blue squares.

2480 dipole
128 tile8128 baseline
2Collecting area 2000m
Maximum baseline 2864m

The final connection to receiver is by means of a standard
three-pin plug and socket.
The CPF houses the MWA post-receiver signal processing equipment within 16 Schroff LHX20 water cooled 19inch cabinets (42U height ×800 mm width × 1 200 mmdepth).
2.2 Array Configuration

The initially envisaged MWA design consisted of 512 tiles
distributed with a r−2 density profile for radii of 50–750 m,with a flat distribution of tiles inside 50 m and 16 outlying
tiles at !1 500-m radius (Lonsdale et al. 2009). This profile
provided smooth uv coverage with a strong concentration ofshort baselines at the scales relevant for EoR power spectrum
measurements (Beardsley et al. 2012), the excellent snapshot
imaging needed for transients and holographic calibration (B.
Hazelton et al., in preparation).
In re-scoping the array to 128 tiles, we maximised sciencecapacity by keeping the key figures of the original layout: exPASA, 30, e007 (2013)cellent snapshot uv coverage, a concentrated core of tiles for
Epoch of Reionisation (EoR) power spectrum measurements,and longer baselines for solar observations. This has led us
to place 25% of the tiles within a dense 100-m diameter core,with a very smooth tile distribution out to 1.5-km diameterand 16 tiles in an outer region of 3-km diameter. The resulting
tile distribution is shown in Figure 3 and the snapshot singlefrequency uv coverage is shown in Figure 4. The coordinatesof the centre of the array are: latitude −26°42′ 11′ ′ .94986;
longitude 116°40′ 14′ ′ .93485; elevation 377.827 m.
Even in the remote Australian desert, there are areas ofrock outcroppings, emergency runways, flood zones, andheritage areas where tiles cannot be placed. Beardsley et al.
(2012) detail a new tile placement algorithm that produces
extremely smooth snapshot uv distributions in the presenceof ground exclusion zones. Noting that over- and underdensities in the uv plane act like two-dimensional wave packets to produce PSF (array beam) sidelobes, the new method
uses a Bessel decomposition of the uv plane to create verysmooth baseline distributions.

0-10-dB

dB-20--30--80-60-40-20 0 20 40 60 80

θ3Images : Tingay et al 2012
2dB10「銀河進化と遠方宇宙」

2017 @ 熊本 アーデンホテル阿蘇 :4 /18 ページdMurchison WideﬁeldArray
20NEBEN ET AL.: MEASURING MWA B
20NEBEN ET AL.: MEASURING MWA BEAMPATTERNS WITH ORBCOMM SATELLITES
Beamforming Errors in MWA Antenna Tiles

Ideal model (zenith)

EW

Observedbeam(zenith)
EW0NS00~20-10-10-10Side lobes-20-20-20-30-30

Primary beam-300Fig. 2.— Ideal (no beamforming errors) beams for a zenith pointing (left) and a representativeo↵-zenith
Neben
et al pointing
2015 & (right)
2016 shsine-projection in units of dB at 150 MHz. The o↵-zenith beam is pointed at (✓, ) = (53 , 101 ).

0Diﬀerence between
0model (line) and observation (points)

antenna element (MWA tile) is a 4⇥4 grid of dualsome frequency dependence across this band, bu
polarization bowtie dipoles with center-to-center spacrelative di↵erences between the sixteen dipole pat
ing of 1.1 m (half-wavelengthat 136 MHz) centered on adistort the beam pattern. The mean gain and group-10-105 m⇥5 m wire mesh ground screen (Figure 1). The sigthrough the 16 signal paths are absorbed into eachdBdB
nals from the 16 antennas (each with a dual-polarization
calibration amplitude and phase. For the same rLNA) are summed-20
in an analog beamformer with segains and group delays of the VNA and measur-20
lectable delay lines, capable of applying phase gradients
cables are irrelevant.
across the grid of dipoles to steer a beam of width fullWe use an Anritsu MS2024A vector network anwidth-at-half-max 25 /(⌫/150 MHz) to elevations as low
set to low probe power (-30 dBm) and 30 trace aver-30-30
as 30 . We characterize the beamformer paths for deThe VNA is optimized for wide band (GHz) me
lay bits 00000 (0 ns) and 11111 (13 ns); the actual EOR
ments, and we mitigate small-scale (sub MHz) syst
corresponding
to elevations above 060 20
are40
typ-60 80
ics through binning to 16 MHz. In each of these win-80-60-40-20 0 delays
20 4060 80 -80-60-40-20
5 ns or smaller, and thus, in between
these two
we average the gains measured at 0.36 MHz resol
θ icallyθcases. Figure 2 shows the zenith beam as well as a repand compute the mean group delay by fitting a
5 /18 ページme「銀河進化と遠方宇宙」
2017phases.
@ 熊本 アーデンホテル阿蘇
resentative o↵-zenith beam. The first field tests on anto the measured
We perform: repeated-10

dB-20

0-10

dB-20

Murchison Wideﬁeld Array
4D. Jacobs

Image
et alFigure 1. An overview of the MWA reionization observation strategy. The background image is a cartesianview: Jacobsof the skyat2016
radioawavelengths and the circles indicate the deep fields observed by the MWA EoR project. Here we are focusing on field 0, centered on Dec-27 and RA 0h. Inset is a foreground subtracted image of the field made using the Real Time System (described more completely in 3.1).
A model of smooth (Galactic and unresolved) emission has not been subtracted and dominates the residual map of this 22 wide image.
Not visible in this average map is variation from channel to channel caused by sources far beyond the field of view which shows up as thewedge in 2d power spectra.
a Visualization compiled from NVSS (Condon et al. 1998), SUMSS (Mauch et al. 2003), and (de Oliveira-Costa et al. 2008)

Three ﬁelds for EoR

Field 0 : centered on Dec -27°, RA 0h
2.4. Interference Flagging

matched to an 「銀河進化と遠方宇宙」
interferometer,2017
which
natively measures
6 /18 ページ@ 熊本 アーデンホテル阿蘇 :ithub.com/miguelfmorales/eppsilon
CHIPS
EmpCov

Cosmological HI Power Spectrum
Empirical Covariance Estimator

github.com/miguelfmorales/FHD
Calibration
github.com/miguelfmorales/eppsilon
12

Calibration process

Jacobs et al 2016

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then「銀河進化と遠方宇宙」
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Drift scan survey with MWA
Drift scan
アンテナのビームの向きをzenithに固定し、空を掃くように観測メリット
・ビームの形が安定しているので、キャリブレーションがしやすい
Beamforming Errors in MWA Antenna Tiles
3・観測領域が広い!

デメリット
・全観測領域で点源のカタログが必要 (EoR ﬁeldの外)Neben etal 2016
Fig. 2.— Ideal (no beamforming errors) beams for a zenith pointing (left) and a representative o↵-zenith pointing(right)
shown inine-projection in units of dB at 150 MHz. The o↵-zenith beam is pointed at (✓, ) = (53 , 101 ).

antenna element (MWA tile) is a 4⇥4 grid of dualpolarization bowtie dipoles with center-to-center spacng of 1.1 m (half-wavelength at 136 MHz) centered on a5 m⇥5 m wire mesh ground screen (Figure 1). The signals from the 16 antennas (each with a dual-polarizationLNA) are summed in an analog beamformer with seectable delay lines, capable of applying phase gradientssome frequency dependence across this band, but onlyrelative di↵erences between the sixteen dipole pathwaysdistort the beam pattern. The mean gain and group delay
through the 16 signal paths are absorbed into each tile’s
calibration amplitude and phase. For the same reason,gains and group delays of the VNA and measurement
cables are irrelevant.
「銀河進化と遠方宇宙」 2017 @ 熊本 アーデンホテル阿蘇 :8 /18 ページ

Drift scan data
Data property
Pointing Center RA,Dec = 0.0, -26.70
Imaging Centerfrom RA,Dec = 23.7, -26.70 to RA,Dec = 1.25, -26.70
Center frequency = 182.415 MHz
Bandwidth = 30.72 MHz
Snapshot :112s
Total : 1.5 hour

「銀河進化と遠方宇宙」

2017 @ 熊本 アーデンホテル阿蘇 :9 /18 ページ

Calibration : ﬂagging
Flagging & Average
AOFLAGGER : Automatic ﬂag coarse band and RFI.
ﬂagging of about 1% of the data
6A. R. Offringa et al.

RFI occupancy per subband

Data averaging(33.4%)87

EoR highDigital TV
RF12RF11RF85

EoR low

RF7

RFI ratio (%)

FMRF6

to reduce data volume

6

ORBCOMM2~4s and 40~80kHz

432

1false
pos
080

100

120

140
160
Frequency (MHz)「銀河進化と遠方宇宙」

180

200

220

Oﬀringa et al 20152017 @ 熊本 アーデンホテル阿蘇 :10 /18 ページ

maps to kk .
The power of this simple formalism is that we can now
map the e↵ects of the primary beam, which enter into
a visibility measurement in a well-known way, to cosmological Fourier space and the power spectrum P (k? , kk ).
Data processes
each112s
snapshots&40kHzchannels
We begin with the form of a visibility in the flat-sky approximation (Thompson et al. 2001)37 :Visibility based CalZVb (⌫) =dl dm A(l, m, ⌫) I(l, m, ⌫) e 2⇡i(ul+vm) , (3)sources nea
contaminat
space. Althwas also fou(2012); Thyusing entire
Equationrive in thisI(l, m) whic
tively atten
Therefore,
where
the primarybeam, point
I is thesources
sky brightness
Ionosphere
calA&isGain
cal by using
those kk mo
distribution, l and m are direction cosines on the sky,
FG model⌫ :iscatalogs
pointsources(PUMA)
be attenuat
frequency,ofandu andv are theprojected baselineof the prim
lengths
onthegroundplane
measuredinwavelengths.
after calibration, model is subtracted from data schematical
We can rewrite this expression in terms of the geometricdelay ⌧g (Parsons & Backer 2009):
ZVb (⌫) =dl dm A(l, m, ⌫) I(l, m, ⌫) e 2⇡i⌫⌧g , (4)RTS Real Time System

MITCHELL et al.: REAL-TIME CALIBRATOR MEASUREMENTS

whereb · ŝ1⌧g == (bx l + by m),cc(5)b ⌘ (bx , by ) is the baseline vector measured in meters(i.e. u Jelic⌘ et(u,v) = ⌫b/c), and ŝ ⌘ (l, m). Doing theal 2008
delay-transform given by Equation 2 gives us a delay「銀河進化と遠方宇宙」

Mitchell et al 20082017 @ 熊本 アーデンホテル阿蘇 :11 /18 ページ

Drift scan data : calibration resultPreliminary

Gray panels show ﬂagged tiles.

x axis : frequency
y axis : amplitude「銀河進化と遠方宇宙」

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Drift scan data : image not peeled
Imaged by RTS
Point sources not peeled

Preliminary
Jy/beam「銀河進化と遠方宇宙」

2017 @ 熊本 アーデンホテル阿蘇 :13 /18 ページ

Calibration : point source
Point source catalogues : PUMA (Line et al 2016)

Line et al 2016

Catalogues :MWA Commissioning Survey
Large Array Low Frequency Sky Survey redux
NRAO VLA Sky Survey
Molonglo Reference Catalogue

Figure 5.: An example of an accepted isolated match. As there is only one possible combination of sources, and that combination has P1 > Pu , thecross-match combination is accepted without investigating the SED.
「銀河進化と遠方宇宙」 2017 @ 熊本 アーデンホテル阿蘇 : 14 /18 ページ

Drift scan data : image with sources
Point sources listed by PUMA

Preliminary
Jy/beam「銀河進化と遠方宇宙」

2017 @ 熊本 アーデンホテル阿蘇 :15 /18 ページ

Drift scan data : peeled image
Peeling 1000 point sources

Preliminary
Jy/beam「銀河進化と遠方宇宙」

2017 @ 熊本 アーデンホテル阿蘇 :16 /18 ページ

Drift scan data : future work
– 23 –First Season MWA E

Power spectrum
DRIPS will be developed
2D power spectrum estimator
based on CHIPS (Trott et al 2016)
Compare with pointing observation

Beardleyet al 2016
Figure 15. One dimensional power spectra for ourthree sub-bands
and bothpower spectrum with step widths corresponding to the bin size used
Trott measured
et al 2016
plot the absolute value with a dotted line. The gray boxes show the ±2 erro
meet the horizontal axis we are consistent with zero. The thin red line is the 1for each k bin. A fiducial theoretical model for a fully neutral IGM from Furlan

2D power spectrum

ria based on catalog resolution and fitting the spectral en-W (left) and N-S (right) cross power spectra when foregrounds are excluded from the estima-band.

17 /18 ページ「銀河進化と遠方宇宙」
2017 @ 熊本
アーデンホテル阿蘇
ergy distribution
to a power-law.
Thesecriteria allow: fortions w

Summary
MWAの観測データを使ったキャリブレーション
Drift scan data
RTS (Mitchel et al 2008)
PUMA (Line et al 2016)
今後のMWA-jpの具体的な活動として、
Drift scan survey data を使ったデータ解析
・Estimate 2D power spectrum
・Compare with pointing observation
Cross correlation with LAE (Kubota+)
Cross correlation with CMB (SY+)
「銀河進化と遠方宇宙」2017 @ 熊本 アーデンホテル阿蘇 :18 /18 ページ