Download IRAS - the infrared - Imperial College London Astrophysics

Cool dusty galaxies: the impact of the
Herschel mission
Michael Rowan-Robinson
Imperial College London
Thessaloniki, Oct 3rd 2009
Cool dusty galaxies: the impact of the
Herschel mission
To set the scene for the Herschel far infrared and
submillimetre mission, I’m going to talk first about
some of the key discoveries from the IRAS and
Spitzer missions
Thessaloniki, Oct 3rd 2009
IRAS
1983 saw the launch of
IRAS, the Infrared
Astronomical Satellite,
which made the first
all-sky survey at
infrared wavelengths,
from 10-100 microns
Thessaloniki, Oct 3rd 2009
IRAS - the infrared ‘cirrus’
emission from clouds
of interstellar dust in
our Galaxy, the infrared
‘cirrus’
south celestial pole
Thessaloniki, Oct 3rd 2009
IRAS - star forming regions
LMC, the Large Magellanic Cloud
Thessaloniki, Oct 3rd 2009
constellation Orion
Uultraluminous
infrared galaxies
IRAS discovered
ultraluminous infrared
galaxies, forming stars
100-1000 times faster
than our Galaxy, probably
caused by mergers between
two galaxies
this is an HST image of
Arp 220
Thessaloniki, Oct 3rd 2009
IRAS - dust debris disks
IRAS also discovered dust debris disks around stars, confirmed by
imaging with the Hubble Space Telescope, evidence for planetary
systems in formation. Today over 300 exoplanets are known.
Thessaloniki, Oct 3rd 2009
IRAS
the IRAS all-sky survey of infrared point-sources: white: star-forming
regions, blue: red giant stars, green: galaxies. IRAS detected 60,000
dusty, star-forming glaxies over the whole sky.
Thessaloniki, Oct 3rd 2009
Thessaloniki, Oct 3rd 2009
SPITZER, 2003
LMC
star formation
in our nearest
neighbour,
the Large
Magellanic
Cloud, seen
at infrared
wavelengths
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IC1396, the Elephant’s Trunk
- a dark globule inside
an emission nebula
- a pair of newly
formed stars have
created a cavity
- the animation shows
how the appearance
changes from the
optical, where dust
absorbs light to the
infrared where the dust
radiates
Thessaloniki, Oct 3rd 2009
QuickTime™ and a
MPEG-4 Video decompressor
are needed to see this picture.
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infrared emission from debris along a comet orbit
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SINGS - Spitzer Nearby Galaxy Survey
• 75 nearby galaxies
• detailed studies of
their gas, dust, and starformation rate
M81
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visible (HST) and infrared (Spitzer) images of M51,
the ‘Whirlpool’ galaxy
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Sombrero galaxy
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Two interacting galaxies
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Visible and infrared images of the star-forming
galaxy Messier 82
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High-redshift galaxies with Spitzer
Spitzer is only an
85-cm telescope,
but it can detect
the most distant
galaxies known
z ~ 6.7
lensed galaxy with M = 109 Mo,
stellar age at least 50 Myr
•
Thessaloniki, Oct 3rd 2009
Egami et al 2005:
SWIRE (Spitzer Wide-Area IR Extragalactic
Survey)
I’ve been mainly involved with SWIRE, a survey of ~50
square degrees of the sky at 3.6-160 microns.
We found 1.5 million galaxies and have used their optical and
near infrared colours to estimate their distances, and hence
their luminosities, star-formation rates, stellar masses and
dust masses
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optical templates for photometric redshifts
t
(Rowan-Robinson et al 2008)
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These are the
galaxy templates
we use for
estimating the
redshift of the
galaxies
Over 1 million photometric redshifts
5 optical bands, + 3.6, 4.5 mm
This shows the kind of
performance we achieve, a
comparison of our
photometric redshifts with
spectroscopic redshifts
Thessaloniki, Oct 3rd 2009
SPITZER-IRS spectra of ULIRGs
•
detailed infrared spectra of
some ultraluminous infrared
galaxies (ULIRGs), and our
models for these
• we need Herschel to test the
behaviourof these galaxies at
submillimetre wavelengths
(Farrah et al, 2008)
Thessaloniki, Oct 3rd 2009
our infrared
templates
star-formation rate v. redshift
• whole SWIREcatalogue
• strong selection effects
• consistent with strong rise
to z = 1.5
(RR et al 2008)
Thessaloniki, Oct 3rd 2009
star formation history as a function of redshift
•
The Infrared Space
Observatory (19969) showed a steep
rise in the starformation rate to z =
1
•
submm surveys and
surveys with Spitzer
show flat behaviour
from z = 1 - 2.5
•
very uncertain at
z > 2-3
•
Herschel surveys
will detect thousands
of high-redshift starforming galaxies
Thessaloniki, Oct 3rd 2009
SOURCE COUNTS AT 24 microns
•
to understand the numbers
of sources as a function of
brightness, different tyes of
galaxy need to undergo
different evolutionary
histories
cirrus
M82
dust tori
Thessaloniki, Oct 3rd 2009
COUNTS AT 8-1100 mm, ir background
160 mm
Predicted counts from 8
1100 microns, comparison
with observed counts at
160, 850 and 1100
microns, and with
integrated background
spectrum
(Rowan-Robinson 2009)
850 mm
1100 mm
Integrated
background
spectrum
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HERSCHEL SPACE OBSERVATORY
Herschel launch May 14th 2009,
now in orbit at L2
Science demonstration phase
started two weeks ago
Thessaloniki, Oct 3rd 2009
HERSCHEL SPACE OBSERVATORY
Composite of M51 with
PACS array
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HERSCHEL SPACE OBSERVATORY
SPIRE
images
of M66
and M74
Thessaloniki, Oct 3rd 2009
HERSCHEL SPACE OBSERVATORY
SPIRE images of M74 (and high redshift galaxies ?) at 250, 350, 500mm
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Messier83
background
galaxies very
clear on latest
image,of M83
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Herschel view of
the Milky Way
Thessaloniki, Oct 3rd 2009
European-ELT: 2017
Proposed 43-m,
segmented mirror,
working at 0.6-23
microns.
Will allow us to
image exoplanets,
take their spectra,
and to see the
very first galaxies
in the universe, at
redshift > 10
Thessaloniki, Oct 3rd 2009