The Transient Radio Sky Astrophysical and Artificial

1
From gas to galaxies
- When and how do disks and bulges form - Do
galaxies form at once or assemble from small to
large - How does the star formation activity
proceed and where - Role of the environment
Radiotelescopes can trace the neutral gas
extremely well and measure the star formation
from the synchrotron emission
unique opportunity for SKA
2
The star-formation history of the Universe

• where does the star formation occur
• how does the SF density evolve
• - do most high-z stars form in large
• galaxies, or in small ones?
• are SF history and gas consumption
• connected?

3
A history of the Universe
Dark Ages
4
Star formation history of the Universe
Star formation beyond z 2 can be probed using
radio continuum
(Baugh et al. 1998)
5
Star formation rates in the Universe
M82 optical

• Starburst galaxies e.g. M82
• Radio VLBI reveals expanding supernovae through
  dust
• Infer star birth rate from death rate rather
  directly
• SKA Image M82s to 100Mpc
• Detect M82s at high z
• Calibrate integrated radio continuum ? SFR at
  high z

M82 VLA MERLINVLBI
6
Local star-forming galaxies ( IRAS galaxies)
(Radio emission is dominated by synchrotron
radiation from electrons accelerated by supernova
remnants)
UGC 09057 NGC 5257/5258
NGC 7252 z0.0054
z0.0223
z0.0161 Derived star formation rate

1.8 Msun/yr 120
Msun/yr 32 Msun/yr
7
Far-infrared - radio correlation for local
star-forming galaxies
L(Radio)
In star-forming galaxies, far-IR and radio
emission are tightly correlated. At star
formation rates above 100 Msun/yr, many
star-forming galaxies also have active nuclei.
Signs are Seyfert-like emission-line ratios and
(sometimes) excess radio emission
ULIRGs
Normal galaxy line (Devereux Eales 1989)
L(IRAS)
(Sadler et al. 2002)
8
Local radio luminosity function of active and
star-forming galaxies
Below 1025 W/Hz, the local radio source
population is always a mixture of AGN and
star-forming galaxies. i.e. There is probably
no observational regime where radio surveys
detect only star-forming galaxies.
1
100 Msun/yr
9
To discriminate star forming galaxies from AGN
the surveys require high resolution resolve the morphology
Spectral index and polarization are not ideal for
discriminating between AGN and star forming disks
Information from other wavebands, such as the
X-ray or the optical, can also help discriminate
the two populations of radio sources
10
Object nature in words
Normal galaxies
on-going stellar evolution
Starburst galaxies (SBs)
enhanced stellar (SNe) activity
...
Seyfert galaxies/QSOs AGN
small-scale core-jets
Radio galaxies quasars RL AGN
large-scale core-jets
LOW ------------------------ radio power
------------------- HIGH
11
Radio AGN
Unsolved problems Radio AGN formation redshift
role in reionisation epoch
? What drives the evolution of AGN ? Typical
lifecycle ? Single or many generations ? How
many populations are weak powerful AGNs same
? Inter-relation between AGN and star-formation
(SF) ? Can we find the first SMBHs?
12
The SKA sky what will we see?
HDF-N 5 x 5 arcmin area to I 29thmagnitude Foma
lont et al., ApJ 475, L5 (1997) 6 sources
detected by VLA with S8.4 12 ?Jy (50 hour
observation)
13
The SKA sky what will we see?
Simulation of 6 x 6 arcmin (UDF-like) area to
S1.4100 nJy Blue star forming galaxies Green
radio galaxies/AGN Jackson (PASA) www.atnf.csiro
.au/people/cjackson
14
From gas to galaxies
- When and how do disks and bulges form - Do
galaxies form at once or assemble from small to
large - How does the star formation activity
proceed and where - Role of the environment
Radiotelescopes can trace the neutral gas
extremely well and measure the star formation
from the synchrotron emission
unique opportunity for SKA
15
Messier 81
DSS
HI
16
Cosmology Ho72 km/s/Mpc ?M 0.27 ?? 0.73
5 ? detection limit for 100 hour integration
z Age lookback 1 SB dimm m-M Dlum M(HI)
Gy time Gy kpc dm Gpc 109 Msun
0.1 12.37 1.29 1.82 0.42 38.29 0.455 0.36 0.2
11.25 2.41 3.27 0.80 39.94 0.973 0.41 0.5 8.
64 5.02 6.09 1.77 42.26 2.83 0.59 1.0 5.92
7.73 8.05 3.03 44.11 6.64 1.2 1.5 4.34
9.32 8.35 4.00 42.21 11.0 3.4 2.0 3.33
10.32 8.48 4.80 45.21 15.8 7.5 3.0 2.18
11.48 7.83 6.05 47.06 25.8 25 4.0 1.56
12.09 7.09 7.03 47.82 36.6 60 5.0 1.19
12.47 6.42 7.82 48.39 47.6 160
17
The 3 brightest S0 galaxies in a volume limited
sample (Verheijen et al.)
How does this fit in with the density
morphology relation and Spiral ? S0 transformation
18
The Amazing NGC 7426
300 h-1 kpc
- Normal Elliptical - Two tails, 185, 125 h-1
kpc in length! - 4 x 109 h-2 Msolar - NHI (min)
1019 cm-2 - Tails aligned with Pisces-Perseus
super cluster structure
Schiminovich et al. in prep.
19
Galaxies around NGC 7426
Diamonds V 5750 Squares 5150 V 20
NGC 5055
Oosterloo et al.
21
MHI 1.8 108 Msun
22
NGC 6946
Boomsma et al.
23
WSRT Mosaic
HI in the Coma cluster z 0.023
Beijersbergen Ph.D. Thesis 2003
24
Maximum redshift for a 360 hour integration with
SKA
2000 galaxies/ deg
M 101
100 000
Star formation with z
30 000
M 51
SMC
Crucial epoch
25
SKA will image galaxies such as M81 and N5055 at
z 26
The Antennae
HI
Star light
Tidal interaction of galaxies in a fatal orbit
produce massive star formation and will End in a
merger.
27
CO in the Antennae
SKA can probe CO Beyond z 4
28
Redshift coverage with 20 GHz as highest SKA
frequency
ALMA redshift coverage
SKA redshift coverage
29
Strawman survey parameters
Shallow surveys one year covering 1000
square degrees
Detect 107 galaxies in 107 Mpc-3
Deep surveys 360 hours ( a month)
Continuum sensitivity 20 nJy
Line sensitivity see folllowing table
30
Detectable HI Masses as a function of redshift in
360 hoursRed-shift Look Back HI Mass Limit
Detections Time (Gyr)
(Msun)0.5 - 1.0 4.2 - 6.2 1.7 108
6.6 105 1.0 - 1.5 6.2 - 7.3
4.7 108 2.3 105 1.5 - 2.0 7.3 -
8.0 1.1 109 1.0 105 2.0 - 2.5
8.0 - 8.5 2.2 109 4.4 104
2.5 - 3.0 8.5 - 8.9 4.1 109
3.0 104 3.0 - 3.5 8.9 - 9.1 6.7 109
1.0 104 3.5 - 4.0 9.1 - 9.2
1.2 1010 9.5 103 4.0 - 4.5 9.2 -
9.3 1.6 1010 7.0 103