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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 Thessaloniki, Oct 3rd 2009 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. Thessaloniki, Oct 3rd 2009 infrared emission from debris along a comet orbit Thessaloniki, Oct 3rd 2009 SINGS - Spitzer Nearby Galaxy Survey • 75 nearby galaxies • detailed studies of their gas, dust, and starformation rate M81 Thessaloniki, Oct 3rd 2009 visible (HST) and infrared (Spitzer) images of M51, the ‘Whirlpool’ galaxy Thessaloniki, Oct 3rd 2009 Sombrero galaxy Thessaloniki, Oct 3rd 2009 Two interacting galaxies Thessaloniki, Oct 3rd 2009 Visible and infrared images of the star-forming galaxy Messier 82 Thessaloniki, Oct 3rd 2009 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 Thessaloniki, Oct 3rd 2009 optical templates for photometric redshifts t (Rowan-Robinson et al 2008) Thessaloniki, Oct 3rd 2009 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 Thessaloniki, Oct 3rd 2009 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 Thessaloniki, Oct 3rd 2009 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 Thessaloniki, Oct 3rd 2009 Messier83 background galaxies very clear on latest image,of M83 Thessaloniki, Oct 3rd 2009 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