Measuring the Gas in Galaxies in the Distant Past Philip Lah Too late. Here comes the SKA.
-
date post
19-Dec-2015 -
Category
Documents
-
view
217 -
download
1
Transcript of Measuring the Gas in Galaxies in the Distant Past Philip Lah Too late. Here comes the SKA.
Who am I?
• I am astronomer with a joint appointment at the:
National Centre for Radio Astrophysics,
Tata Institute of Fundamental Research, India
and the
Research School of Astronomy & Astrophysics,
Mount Stromlo Observatory,
Australian National University
• I use both radio and optical telescopes for my research
Atmospheric TransmissionA
tmos
pher
ic O
paci
ty
0 %
50 %
100 %
1 nm 1 μm 1 mm 1 m 1 km
Wavelength →← Frequency
radio
optical
infraredgamma rays, X-rays
& ultraviolet
Hydrogen Gas in the Universe
Hydrogen 76% by mass of the baryons – normal matter
(that is not the weird stuff – Dark Matter)
Neutral Atomic
Hydrogen Gas
produces emission at a wavelength of 21 cm
Hydrogen Gas in the Universe
Hydrogen 76% by mass of the baryons – normal matter
(that is not the weird stuff – Dark Matter)
Neutral Atomic
Hydrogen Gas (HI)
produces emission at a wavelength of 21 cm
21 cm
Atmospheric TransmissionA
tmos
pher
ic O
paci
ty
0 %
50 %
100 %
1 nm 1 μm 1 mm 1 m 1 km
Wavelength →← Frequency
radio
optical
infraredgamma rays, X-rays
& ultraviolet
HI Gas and Star Formation
neutral atomic hydrogen gas
cloud (HI)
molecular gas cloud (H
2)
star formation
21 cm
Atmospheric TransmissionA
tmos
pher
ic O
paci
ty
0 %
50 %
100 %
1 nm 1 μm 1 mm 1 m 1 km
Wavelength →← Frequency
radio
optical
infraredgamma rays, X-rays
& ultraviolet
redshifted
Coadding HI signals
velocity
z1
z2
z3
flux
velocity
Coadded HI signal
z1, z2 & z3 optical redshifts
of galaxies
HI blue outside x-ray gasblue galaxies surrounding the core of a large galaxy cluster
galaxies observed as they were 4 billion years
ago
coadding signal from 94 galaxies
HI blue outside x-ray gasblue galaxies surrounding the core of a large galaxy cluster
galaxies observed as they were 4 billion years
ago
coadding signal from 94 galaxies
The SKA and Me
• SKA`s collecting area 20GMRT`s collecting area
• SKA better receivers
• SKA larger field of view
• SKA better RFI environment
The SKA and Me• my current research looking at galaxies 3 to 4 billion years ago –
SKA directly detect HI signal
• originally SKA proposed to detect HI gas from 8 billion years ago
• stacking with SKA ~12.7 billion years ago, the era of first galaxies
SKA
fully operational
2024