Netherlands Institute for Radio Astronomy

Radio surveys: an overview
Raffaella Morganti
ASTRON (NL) and Kapteyn Institute
ASTRON is part of the Netherlands Organisation for Scientific Research (NWO)
Sunday, 21 October 12

Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012

Turning points for radio surveys!
Surveys (and deep fields) have played also in radio astronomy
an important role

• .....now we are at a turning point:• entering a new era of surveys !
• - new technology (e.g. wide field of view, broad bandwidth, high data rate etc.)•=> larger+deeper surveys can be done (line, continuum, polarisation,transients, serendipitous!...)• - delivering a broader variety of products•=> revolutionise the field: amazing databases for the community

These changes have already started!
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12•This talk:• - radio surveys so far:•Radio continuum, line (HI)• - what is coming up now/soon•

One survey fits all - challenges in handling the many
products from new radio surveys......

• See also talks from R. Taylor, M. Wiseand J. van Leeuwen
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

Radio surveys key ingredients• Limitations up to now:
➡ spatial resolution often low/poor➡ compromise in sensitivity => field of view => observing time
➡ limited frequency coverage & bandwidth => penalised magnetism, RM synthesis,
spectral index...
➡ no multi-epoch => penalised transients

R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

Radio continuum surveys
REF!!!

Norris et al. 2011

Deepest radio
fields @ 1.4GHz

NVSS
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12WENSS

Largest radio
surveys @ 1.4GHz

Radio continuum surveys (an incomplete list)
SurveyNVSS (NRAO VLA Sky Survey)

Freq.
1.4 GHz

FIRST (Faint Images of the Radio

1.4 GHzArea
δ>-40deg

5sigma2.5 mJy

5 arcsec

1mJy

54 arcsec*cosec(dec)
80 arcsec

18 mJy43 arcsec*cosec(dec)
70 arcsec

5 mJy

5 arcmin

150 mJy(1 Jy= 10-26 W m-2 Hz-1)‫‏‬

Sky at Twenty-cm)

WENSS (Westerbork Northern Sky 325 MHz

Spatial resol.
45 arcsec

3.14 sr, δ>+30deg

Survey)VLSS
Text

74 MHzδ> -30deg

SUMSS (Molonglo Sky Survey)

843 MHzδ< -30 deg

Cambridge 7C

151 MHzδ> +20 deg

PMN (Parkes-MITNRAO)

4850 MHz~all sky

100 mJy

125 mJysee also Condon 2010 for a review...
Most of the surveys at low frequencies, up to 1.4 GHz (compromise between area, observing time,R.
spatialMorganti - resolution
Data Intensive Astronomy
and -sensitivity
SpS5 IAU GA, Beijing=>Augfuture
2012
surveys will also concentrate on this frequency range
Sunday, 21 October 12

Current major 20cm continuum surveys‣In addition to surveys: deep
fields => situation so far
COSMOS
HDF-N/S

Increasing area

BootesLockman HoleSpitzer First Look
ATLAS
etc.

only ≤10deg2 of sky covered so
far in such a depth (~10-50 µJy)

Increasing sensitivity
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

Norris et al. 2011

Diagram courtesy of Isabella Prandoni

Why continuum surveys? ....
Earliest radio surveys => major impact onunderstanding radio-loud AGN (radio galaxies andquasars)

Radio AGN different fromothers: evolutionary
sequence?

Radio sources stronger than ~1 mJy @ 1.4 GHz
are typically powered by an AGN

Miley et al.

Bridle• Identify high-z AGN via steep
spectrum => TN J0924-2201 at z=5.2, the HzRG with the

Rottgering et al.

highest redshift known to date.

• Life cycle of AGN• Radio halo in clusters• ....too many to list all....

R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

Selected radio power > 1023.8 W/Hz
Hickox et al. 2011

Why continuum surveys? ....
Earliest radio surveys => major impact onunderstanding radio-loud AGN (radio galaxies andquasars)

star-forming galaxies

AGN

Radio sources stronger than ~1 mJy @ 1.4 GHz
are typically powered by an AGN
Condon 2011

As the surveys probe the fainterend, the nature of the detectedradio sources changes:
starforming galaxies (change
in the counts slope) together
with radio-quiet AGN=> evolution of star formation
can be studied
Padovani et al 2009, Prandoni et al. 2009,
Seymour et al. 2008
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

Prandoni et al. 2012

Limited possibilities for polarisation studies
Galactic B poorly known but is important in most processes in the interstellar medium
Measure rotation measure against many extragalactic sources
so one can reconstruct Galactic magnetic field(“The Rotation-Measure Grid”)
Studies so far done using thetwo bands available in the
NVSS (Taylor et al.)More frequencies andbroad band needed will be
provided by the new radio
telescopes/surveys:
accurate determinationof rotation of polarisation vector overthe band due
to magnetised plasma

R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12Z

Bk ne dl

(Taylor++)Limited possibilities for radio transients
ATA survey
Allen Telescope Array: 11-epoch deep fieldobservations 700 sq deg (Croft+ 2010).
No transients > 40 mJy

But they do occur!

Need for more sensitivity, cover larger areaand sample different time domain.
R. Morganti- Data Intensive
Astronomy- SpS5 IAU every
GA, Beijing Aug
2012
e.g.
ASKAP
can
do NVSS
day….
Sunday, 21 October 12

Serendipitous detection of flare star with WSRT

Radio surveys: line (HI)Blind line (HI) surveys• largest HI surveys are single dish => nospatial information• Limited/No morphological information• Limited sensitivity• Only ‘local’ Universe, no evolution
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

Radio surveys: line (HI)RA

Blind line (HI) surveys

Freq• largest HI surveys are single dish => nospatial information
what we would
really like to have....
Dec
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12• Limited/No morphological information• Limited sensitivity• Only ‘local’ Universe, no evolution

Main blind HI surveys
Recent HI surveys have large field of view provided bymultibeam systems but very limited spatial resolution all single-dish:• HIPASS (Parkes) - 2/3 of the sky, out to 12700 km/s
(z~0.04; velocity resol. ~ 13 km/s) spatial res.~15
arcmin, rms noise 13mJy=> 5317 extragalactic detections HI emission
2
AlfAlfa(Arecibo):
7000
deg
z~0.06, spatial•
resolution ~ 3 arcmin, rms 1.6 mJy/ch=> expected 30000 extragalactic detections HI
emission (15000 so far, 40% release; Haynes et al.)

• HIJASS (Jodrell)• Effelsberg Bonn HI survey
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

Alfalfa footprint and Sloan (red)An incomplete list of highlights.....

‣from HIPASS and Alfalfa (extragalactic) ...
‣ statistics of gas rich galaxies‣ scaling relations (dependency of HI as function of size,

Galex/Arecibo/SDSS survey
Catinella et al. 2010,2012

concentration, colour, ...)‣ role of environment‣ HI mass function‣ no “dark galaxies”, stacking ...
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

Statistics only known down to 106 M☉

ALFALFA (Martin++ 2010)

...but the morphological/kinematical information is important!
Surveys of sample of galaxies: very time consuming evenfor relatively small samples (a few hundred objects)

WHISP survey- Role of gas (HI) in galaxy evolution and role of environment- Gas and starformation- Gas accretion- Show the internal workings of galaxies

Accreting HI around
NGC891, Oosterloo et al.

Sauron and Atlas3D survey of early type galaxies
Oosterloo et al. 2010, Serra et al. 2012
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12....importance of multi-wavelength information!

In summary, as reference.....

Where we are now‣ Number sources detected in 1.4GHz surveys=> NVSS: 1.7x10

6‣Number sources at low freq
555=> SUMSS ≳ 10 , WENSS: 2x10 , VLSS ≲10‣ Number HI detections (single dish profiles)=> 5317 HIPASS=>30000 Alfalfa+ other much smaller samples but providing
imaging (a few hundred objects)
We know about H I in 2 x104 galaxies,~100 above z = 0.1!!!
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

Entering the new era!

R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

Some surveys coming up soon....
Low frequencies continuum surveys:‣ TGSS - GMRT survey 150 MHz about 32,000 sq. deg of the sky north of declination of -30

degrees and reaching an rms noise of 7-9 mJy/beam at an angular resolution of about 20 arcsec. Whencomplete, the survey is expected to detect more than 2 million sources (Sirothia et al. )‣ LOFAR continuum surveys (~20-150MHz)=> LOFAR Calibration survey - MSSS - already started

1.4 GHz surveys

Simultaneously observing line
‣ continuum surveys => Aperif, ASKAP.... and continuum to optimise‣ Line surveys => Apertif, ASKAP....
observing time!!

R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12.....and other radio telescopes will be alsointeresting for deep fields

TIFR GMRT Sky Survey (TGSS)‣TGSS - GMRT survey 150 MHz about 32,000 sq. deg of the sky north of declination of -30 degrees
and reaching an rms noise of 7-9 mJy/beam at an angular resolution of about 20 arcsec. When complete,
the survey is expected to detect more than 2 million sources (Sirothia et al. )Released so far

R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

LOFAR Core (Aug 2011)

HBA

LBA

R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 1221

Surveys with LOFAR

Rottgering et al.

LOFAR 60 MHz 3x3 deg,
rms 20-30 mJy/b
Shulevski et al.

HBA (140 MHz) 7 hrsBW = 31 MHz
3°x3° (inner part of FOV)
res=24´´ × 21´´
Rms=0.8 mJy/beam ~103 sources
Orru`, Falcke et al.

In addition to the increased number ofsources, synergy with transient (multi-epoch
observations) and magnetism.
LBA 60 MHz (~30 mJy/beam, ~80 arcsec resolution)
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

22

LOFAR Multifrequency Snapshot Sky Survey (MSSS)
Fully automatic pipeline to produce global sky model

SurveyMSSS-LBA
Field of view per field (FWHM)
5.77° @ 60 MHz
Sensitivity
15 mJyResolution<100’’
Bandwidth per field
16 MHzNumber of simultaneous fields
3Time per field
9 x 11 min
Required number of fields
660
Required
on-source
observing(hr)Aug363
R. Morganti - Data
Intensive Astronomy- SpS5 IAUtime
GA, Beijing
2012
Sunday, 21 October 12

MSSS-HBA
2.42° @ 150 MHz
5 mJy<120’’
16 MHz3
2 x 7 min3616
281

G. Heald & LOFAR MSSS TeamMSSS: LOFAR’s First Survey§ See http://www.astron.nl/~heald/msss/msssmap_lba_obs.html§ Multifrequency: 16, 2-MHz bands 30-180 MHz
Throws open a HUGE new frequency window(courtesy G. Heald)

66 MHz§ Snapshot: Multi-epoch short observation mode
Groundbreaking search for transient sources§ Sky: Quickly cover entire northern sky
LOFAR’s first all-sky catalog, from the mostsensitive survey at extreme low frequencies§ Survey: First large LOFAR imaging program
Paves the way for still deeper surveys...

First large-scale test of production
systemPopulate the global sky model
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 1210x10 degrees, ~100 mJy/beam, beamsize ~ 60 arcsec

!
LOFAR Raw Data Volumes ailsted
• 2688 dipoles (LBA), 200 MHz sampling, 2 polarizations, 12 bit digitizationrof
13 Tbits/s ~ 1.6 TB/s ~ 138 PB/dayesi(up to 244)
• 48 stations, 48 MHz total bandwidth, 8 independent beamsWle
1 sec correlator dump-time• 1128 baselines, 242 sub-bands, 256 channels, 4 polarizations,ah~ 10 TB/hr ~ 240 TB/day ~ 0.1cEB/yr
i
M
m
o
r~1
Storage limits give afLong Term Archivenweek processing
window
o
i
t
a
t
n
e
s
LOFARreis a pathfinderpfor edata-intensiveeSastronomy!
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

Future large 20cm-band surveys
Combining continuum and line

One survey fits all!

R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

Major 20cm continuum surveys for SKA pathfinders

Continuum all-sky surveys for the
SKA pathfinders/precursors=> ASKAP (EMU)/Apertif (WODAN)=> of the order of 100 million sources
will be detected! (for rms~10 µJy overthe ENTIRE sky....)

Increasing sensitivity

Increasing sensitivity

R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

s
er
th
fin
d
pa
A
SK

source counts (Norris et al. 2011)

Increasing area

Estimate of the number of sources
detected e.g. based on the extrapolation of

WODAN

Norris et al. 2011

Diagram courtesy of Isabella Prandoni

New possibilities for radio transients
explored, particularly for short‣ The transient radio sky✓is poorly◆transients

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for fast‣ Need large field of view to find them AND dedicatedLhardware
transients

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array
gives
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flexibility
forinnovative
observing modes:
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‣many station beamsmo‣incoherent addition
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Example of what we areitaplanning
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R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

!
s
l
i
ta

Exciting times ahead for HI work
‣ ASKAP & Apertif will survey HI over ENTIRE sky, uniform properties over entire sky‣ Expected 106 galaxies, out to z ≥ 0.6, most above z = 0.1,
‣ in addition:

15 arcsec resolution (resolved).

H I absorption candidates out to z = 1‣ + deeper surveys of smaller regions out to z = 1‣ Large field of view and large bandwidth.
given collecting area, the spatial resolution of ASKAP & Apertif is near
optimum for surveys of neutral hydrogen.
Can be done together with continuum surveys‣ Major new opportunity: can image the entire sky at high resolution, highsensitivity and out to large distances. EVOLUTION
Heavens et al.
Sunday, 21 October 12

Increase of discovery potential

White ➜ all-sky surveys (wallaby/
askap, apertif ...)Red ➜ large areas deeper surveys

300

MH
z

R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

AlfalfaIn summary, as reference.....

‣

Low frequency surveys: 106 to 107
sources

Where we are now‣ Number sources detected in 1.4GHz surveys‣ 1.4 GHz surveys: likely reaching 10

8=> NVSS: 1.7x106

sources‣Number sources at low freq
555=> SUMSS ≳ 10 , WENSS: 2x10 , VLSS ≲10‣ Number HI detections (single dish profiles)=> 5317 HIPASS=> 30000 Alfalfa+ other much smaller samples but providing
imaging (a few hundred objects)

We know about H I in 2 x104 galaxies, ~100 above z = 0.1!!!

R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

Where we will be soon

‣Number HI (emission) detections:
106 galaxies, out to z ≥ 0.6

HI absorption out to redshift z~1...and most of these HI detection will bespatially resolved! a major change in thescience we can do!

They will obtain information about the line and continuum
simultaneously. We can study gas content and non-thermal
activity at the same time.

Getting ready for these changes: COSMOS Field, pilot EVLA
surveyB array observations (5’’ resolution) z=0 (0.4 kpc) z=0.2 (22 kpc)
50 hours on source ➜ 2.5 Tb of data
Correlator setup: 32 spectral windows covering 1190-1420 MHz➡ 230 MHz => Velocity coverage 58000 km/s
(0<z<0.19)➡ 16384 channels➡ 3.5 km/s velocity resolution
Noise line: 0.2 mJy/beam/ch
Column density: 6 x 1019 cm-2
Noise continuum: μJy level!

van Gorkom, Fernandez et al.
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

WSRT
regioninteresting limits....

Originally continuum observations!
down to 10 microJy (more than 6000 radio sources)
Thanks to the broad band => HI for free up to redshift~0.1 (not many single detection so stacking techniques
used => SDSS spectra for stacking

Radio power
Example: WSRT data Lockman Hole
(HIat
for10freefrom the22 W/Hzpeakedcontinuum observations, see poster)+ SDSS spectra
Mostly sub-mJy sources

Making use of the relatively broad band=> covering redshift up to 0.1
500

400

300
S (µJy)STACKING RED GALAXIES (0.06<z<0.09):
HI easily detected in active (LINERS)No HI in “inactive” objects

Stacked profile
HI detection of galaxies with SDSS
redshift available (about 150)

200

100

0

-100

1410

1420
i (MHz)1430

HI Detection at z=0.1

Gereb,
Noise ~10
µJyOosterloo, Morganti et al. 2012
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12

Gereb, Oosterloo, Morganti

Lockman Hole observed with the WSRT @1.4GHz - 6 deg2 (Guglielmino et al. 2012)

Getting
ready
for
these
changes:the
LockmanHole
When everything else fails: using stacking we can reachFinal remarks✓ Great input from radio sourveys and deep field => now ready for the next major
step forward✓ Unprecedent possibilities for polarisation and transients....
✓ The possibility of performing simultaneously line and continuum observations has great
potential (major step forward especially for line surveys...)✓ Not only more sources but also different way to characterise objects => so morescience!....

✓ Large fraction of the HI detections will be spatially resolved: more possibilities forstudying the properties of the objects!

✓ Connecting much better with surveys at other wavelengths: crucial products will be
provided by the radio.

Ray Norris is organising a new working group on radio surveys: if
you are interested to be part, get in touch with him
R. Morganti - Data Intensive Astronomy - SpS5 IAU GA, Beijing Aug 2012
Sunday, 21 October 12