measuring the gas in galaxies in the distant past
DESCRIPTION
Measuring the Gas in Galaxies in the Distant Past. Philip Lah. Too late. H ere 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 a nd the - PowerPoint PPT PresentationTRANSCRIPT
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 Gasin the
Universe
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 21-cm Emission From Galaxies
Galaxy M33: optical
Galaxy M33: HI 21-cm emission
Galaxy M33: optical and HI
Galaxy M33: optical
Why Study Neutral Atomic Hydrogen Gas?
HI Gas and Star Formation
neutral atomic hydrogen gas
cloud (HI)
molecular gas cloud (H
2)
star formation
Redshift, Observing the Past
The Expanding Universe
Hubble`s Lawredshift velocity related to distance
distance related to age(due to light travel time)
Hubble`s Lawredshift velocity related to distance
distance related to age(due to light travel time)
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
The History of
Star Formation in the Universe
Star Formation Rate Density
Star Formation Rate Density
~10 times current rate
The Amount of
HI Gas in the Universe
HI Gas Density
HI Gas Density
~2 times current density
HI Gas Density
HI Gas Density
region where I have been
working
Current Observations
Giant Metrewave Radio Telescope
Giant Metrewave Radio Telescope
Coadding HI signals
Coadding HI signals
RA
DEC
Radio Data Cube
Frequen
cy
HI red
shift
Coadding HI signals
RA
DEC
Radio Data Cube
Frequen
cy
HI red
shift
positions of optical galaxies
Coadding HI signals
frequency
flux
Coadding HI signals
frequency
flux
z2
z1
z3
z1, z2 & z3 optical redshifts
of galaxies
Coadding HI signals
velocity
z1
z2
z3
flux
z1, z2 & z3 optical redshifts
of galaxies
Coadding HI signals
velocity
z1
z2
z3
flux
velocity
Coadded HI signal
z1, z2 & z3 optical redshifts
of galaxies
My Current Best Observation
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
Future Observations
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
The SKA pathfinders
MeerKAT
South African SKA pathfinder
• 13.5 m diameter dishes
• 64 dishes
• finished 2014 (2018)
ASKAP• 12 m diameter dishes
• 30 dishes
• focal plane array
• finished 2013