Surveys
Staff at the University of Hertfordshire are leading several international surveys covering the whole range of interests within the department.
UH is an international leader in survey astronomy, particularly in the near-infrared where we host three of the six principal investigators of the public surveys being conducted on the new 4-m VISTA near-infrared telescope at Paranal, Chile and two principal investigators of the surveys currently being conducted on the UK Infrared Telescope in Hawaii. Together the VISTA and UKIRT surveys will use >1000 nights over the next five years to conduct detailed studies of the Galactic Bulge and Plane, the Magellanic Cloud System along with a deep multi-band extragalactic survey and a search for exo-planets. A further theme of the the Centre's survey activities is the multi-wavelength view of the Plane of the Milky Way: the Centre is also home to the PIs of optical surveys, north (INT) and south (VST) and a JCMT sub-millimetre survey, covering similar sky areas to the NIR Galactic Plane surveys. A brief outline of our surveys are given below.
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Left: Illustration of the public surveys to be conducted with the VISTA near-infrared survey telescope at Paranal, Chile. CAR staff lead three of these surveys (VVV, VMC and VIDEO; see below) and are heavily involved in all of the others. Right: The VISTA telescope at Paranal, Chile. |
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Surveys for Extra Solar Planets
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Hugh Jones is co-Principal Investigator of The Anglo-Australian Planet Search.
The Anglo-Australian planet search is targeting 250 nearby stars brighter than V=7.5 in the Southern Hemisphere. A Jupiter-like planet exerts a small gravitational pull on its parent star, causing the star to wobble with a velocity of 1 to 100 meters per second depending on the orbital distance and mass of the planet. This motion can be detected via the Doppler Effect. The light emitted by a star moving toward the Earth will be Doppler shifted to shorter (bluer) wavelengths, while a star receding from the Earth will emit light shifted to longer (redder) wavelengths. The effect is extremely subtle and has no effect on the apparent colour of the star. A star with a Jupiter-mass planet will be revealed by the periodic Doppler shift of its light. After one or two orbital periods the information from the Doppler measurements allows us to calculate the orbit and the mass of the unseen planet. Our current measurement precision is 3 meters per second (a brisk walk). For comparison, Jupiter causes the Sun to wobble with a velocity of 12.5 meters per second over a 12 year period. Saturn induces a 2.7 meter per second wobble on the Sun with a 30 year period. The other planets are too small to produce a measurable effect on the Sun.
David Pinfield is the Principal Investigator of the WFCAM Transit Survey.
Galactic Surveys
Phil Lucas is head of the UK Infrared Deep Sky Survey (UKIDSS) Galactic Plane Survey (GPS) implementation group and co-Principal Investigator of the Vista survey "Vista Variables in the Via Lactea" (VVV).
The (UKIDSS) Galactic Plane Survey (GPS) is surveying 1800 square degrees of the northern and equatorial Galactic plane at latitudes -5<b<5 in the J, H and K bandpasses with the UKIRT Wide Field Camera. Running from 2005-2012, it will provide a catalogue of 3 billion sources, which constitutes the largest catalogue of unique sources in astronomy. The GPS data will be combined with a growing array of international Galactic Plane surveys in wavebands from the optical through the mid and far infrared to the submm and radio. As the largest database, the GPS will be the primary Legacy database for all studies of Galactic stellar populations. Some of the main science aims are to determine the environmental dependence of star formation, and to map the inner structure of the Milky Way.
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Left: The Wide Field Camera (long black tube) on the United Kingdom Infrared Telescope on Mauna Kea, Hawaii. Right: Central region of the full WFCAM tile, showing dramatic clouds of gas and dust illuminated by stars in the southern half of the Orion nebula. This is an image at three infrared wavelengths (red represents narrow-band emission from molecular hydrogen gas at 2.12 microns, green represents K-band emission at 2.2 microns, and blue represents J-band emission at 1.25 microns). The region is 11 light years across. |
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The VVV survey is a public synoptic survey of 1 billion stars in a 520 square degree area of the Galactic Bulge and the adjacent southern mid-plane. It is a joint Chilean/European collaboration using the 4-m ESO VISTA telescope. The area includes the 150 square degree Spitzer GLIMPSE-South and GLIMPSE-II mid-IR survey regions. It will provide a single epoch of imaging in the ZYJHKs passbands, followed by 80 epochs of Ks band imaging. It is designed to detect and characterise all stars that vary on timescale between a day and several weeks. It will focus in particular on RR Lyrae variables in the Bulge and Cepheid variables in the plane, and use these to map the structure of the Bulge and the galactic spiral arms in 3-D. The data will also enable star formation studies similar to those of the UKIDSS GPS, but with the advantage that the variability data will detect the more evolved pre-main sequence stars that are not identified by the GPS or by mid-IR imaging. VVV is the largest synoptic survey to date.
Janet Drew is the Principal Investigator of IPHAS + VPHAS
The nearly-complete INT/WFC Photometric H-alpha Survey of the Northern Galactic Plane (IPHAS) is a massive imaging programme being carried out, in narrow-band H-alpha, and broadband r and i filters, using the Wide Field Camera (WFC) on the 2.5-metre Isaac Newton Telescope (INT). The area surveyed is the entire northern Plane within +/- 5 degrees of the Galactic Equator (1800 square degrees). An online summary of IPHAS is available here, and it is described more fully by Drew et al (2005, MNRAS, 362, 753). This will be followed in the next few years by, VPHAS+, an analogous 5-filter survey of the southern Galactic Plane on the VLT Survey Telescope (VST) using OmegaCam. Together, these surveys provide a springboard to a quantitative revolution in our understanding of the extreme phases of stellar evolution, and the means to pursue wide-ranging studies of Galactic Plane stellar populations. The previous generation of H-alpha surveys of the Galaxy, conducted over 30 years ago, begin to be incomplete at visual magnitudes of 12-13: the new generation extends this limit down to red magnitudes fainter than 20 - an increase in sensitivity by a factor of around 1000.
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A false-colour composite of the sky in the vicinity of the HII region, IC 1396B, in Cepheus, combining the r, i and H-alpha imagery from IPHAS. This nebulous region is a star-forming nursery, in which the diffuse emission (coloured orange/yellow) is due to hydrogen atoms excited by the far ultraviolet light from newly-created hot massive stars. The image scale here is roughly 15 x 15 square arcminutes, with N to the left and E down. (picture credit: Nick Wright, University College London) |
Mark Thompson is the Principal Investigator of the SCUBA-2 "All-Sky" Survey (SASSy).
SASSy is an 850 micron survey of initially 4500 square degrees using SCUBA-2 to a 1-sigma depth of 30 mJy/beam. The survey region is in the form of two 10 deg wide strips, one along the Galactic Plane and one perpendicular to the plane at the latitude of the NEP. The survey is optimised to take advantage of poorer weather. The goals are to determine the number & distribution of infrared dark clouds in the galaxy, identify unknown populations of star formation, search for extreme luminosity high-z galaxies, and provide high resolution foregrounds for Planck.
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The regions that will be mapped during the pilot phase of SASSy overlaid on an all-sky projection of the IRAS 100um sky. The Galactic Plane-Wide survey is shown by a red outline and P2P is outlined in black. |
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Mark Thompson is Survey Manager of the JCMT Plane Survey (JPS).
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The JPS is a 450 & 850 micron deep survey of the galactic plane to 1 sigma 4 mJy/beam. Initially to cover two regions (GLIMPSE-N and FCRAO Outer Galaxy Survey) and to be extended to the entire plane visible to the JCMT. The goals are to identify massive star forming regions in the Galaxy and, along with supporting data from other surveys, to determine an evolutionary sequence for massive star formation and its role in triggering further generations of star formation.
Local Galaxies
Maria-Rosa Cioni is the Principal Investigator of the VISTA survey of the Magellanic System (VMC).
The Magellanic Cloud system represents the nearest template for the study of stellar populations and galaxy interactions. Its low metallicity and nearby distance are key issues to exploit the unique VMC data. This survey aims to obtain Y J Ks -band photometry across the system down to Ks = 20.3 at S/N= 10. This sensitivity corresponds to the bottom of the red giant branch field stellar population and allows us to determine the global spatially resolved star formation history with unprecedented quality (~20 per cent errors at a resolution of 0.2 dex in age) and to construct a three-dimensional map of the system. A wide-area (184 square degrees) encompassing the D25 as well as major features delineated by the distribution of stars and HI gas, will both trace the structure of the galaxies and signatures of past and present interactions. Contemporary optical and kinematic observations of comparable sensitivity (e.g. VST) will provide the community with a superior database for future studies of the system and will give us an excellent insight as to what has happened elsewhere in the Universe.
Distribution of VISTA tiles across the Magellanic System (LMC, Bridge, SMC and Stream). Underlying small dots indicate the distribution of carbon stars (black), stellar clusters (blue) and associations (red) while thick dots show the location of observations to be performed with the VLT Survey Telescope (VST) in the optical domain. |
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Elias Brinks is co-Investigator of THINGS.
THINGS, short for "The HI Nearby Galaxy Survey", is a Legacy Programme at the NRAO VLA to perform 21-cm HI observations of the highest quality ( <6'' angular, <5 km/s velocity resolution) of nearby galaxies. The goal of THINGS is to investigate key characteristics related to galaxy morphology, star formation and mass distribution across the Hubble sequence. A sample of 34 objects with distances between 3 and 14 Mpc have been observed, covering a wide range of properties. THINGS data are being used, among other things to investigate the small-scale structure of the ISM, its three-dimensional structure, the (dark) matter distribution and processes leading to star formation. THINGS is designed to complement SINGS, the Spitzer Infrared Nearby Galaxies Survey.
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Extragalactic Surveys
Matt Jarvis is the Principal Investigator of the VISTA Deep Extragalactic Observations (VIDEO) Survey. (Students: Sam Hickey and Glen Parish).
The VIDEO survey is a 13 sq.degree, Z,Y,J,H,K survey specifically designed to enable galaxy and cluster/structure evolution to be traced as a function of both epoch and environment from the present day out to z=4, and AGN and the most massive galaxies up to and into the epoch of reionization. With its depth and area, VIDEO will be able to fully probe the epoch of activity in the Universe, where AGN and starburst activity were at their peak and the first galaxy clusters were beginning to virialise. VIDEO therefore offers a unique data set with which to investigate the interplay between AGN, starbursts and environment, and the role of feedback at a time when it is most crucial. The multi-band nature of the survey ensures many key science drivers can be tackled using the survey alone, without recourse to data from other wavebands. However, the survey fields have been carefully selected to ensure a good RA spread and mix of fields with existing multi-band data thereby enhancing the usefulness of the survey to the whole of the astronomical community, and with an eye to future use of other ESO facilities such as APEX and ALMA. The area and depth means that VIDEO fits naturally between the VIKING and Ultra-VISTA surveys, and has been allocated >200 nights over the next five years.
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The three areas of sky over which the VIDEO survey will be carried out. From left to right; XMM-LSS (~4.5 square degrees), Chandra Deep Field South (~3 square degrees) and Elais-S1 (~4.5 square degrees). |
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Matt Jarvis is the lead scientist in a collaboration between Univs. Edinburgh, Liverpool John Moores and Oxford, on a VISTA narrow-band survey to find galaxies within the cosmological "Dark Ages".
We are undertaking a deep extragalactic survey utilizing a dual set of custom-made narrow-band filters in the Y-band. We will utilize the clean part of the sky spectrum between 969nm < lambda < 991nm, with the principal aim of detecting Lyman-alpha emitting galaxies at 6.97 < z< 7.15. This is more distant than any spectroscopically confirmed object in the Universe (the record currently stands at z = 6.96; Iye, Ota & Kashikawa 2006). The wide-field of view, the blue-sensitive near-infrared detectors and the 4-m aperture of VISTA make this the ideal instrument to probe into the epoch of reionization through narrow-band imaging searches and place the first constraints on the luminosity function and clustering of the most distant star-forming galaxies. Moreover, our dual filters will also be able to find other prominent emission lines at a range of other redshifts, such as [OII] at 1.6 < z < 1.66, H-beta at 0.99 < z< 1.04, [OIII] at 0.94 < z < 0.98 and H-alpha at 0.48 < z < 0.51, which will enable a wealth of other investigations to be carried out, such as the evolution in star-formation rate over large scales traced by H-alpha, the Butcher-Oemler effect in distant galaxy clusters, and the search for distant galaxy clusters via [OII] emission.
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Illustration of the wavlengths probed by our narrow-band filter survey (blue stripes). The black solid line is the atmostpheric transmission at these wavelengths and the red line are OH emission lines from the atmosphere. The blue stripes are positioned to avoid the OH lines and also the regions of poor transmission. |
Matt Jarvis is the Principal Investigator of The Spitzer-Herschel Active Galaxy Survey. (With Jason Stevens, Robert Priddey and students Peter Herbert and Alex Street.)
We have constructed a well-defined sample of radio-quiet quasars from the Sloan Digital Sky Survey, spanning two decades in optical luminosity at a single cosmic epoch, to constrain luminosity dependent effects on the hot dust emission from the obscuring torus, without caveats of luminosity-redshift degeneracies, a fundamental problem in flux-density limited sample. Crucially, we have also defined a sample of radio-loud quasars selected in exactly the same way as the radio-quiet quasars, allowing us to address what effect radio emission may have on the dust properties of quasars. Finally, by selecting a sample of radio galaxies matched to have the same distribution in radio luminosity as the radio-loud quasars we will determine how orientation influences the near- and mid-IR SEDs, and in particular obtain a firm hold on the geometry of the obscuring torus. Thus, this data will allow us to directly address all facets of AGN unification. This project has already been allocated 43 hours of Spitzer Space Telescope time and will be submitted as a Herschel Open Time Key Project in Oct 2007.
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Spectral Energy Distribution of a radio galaxy and quasar from SHAGS highlighting the emission from warm dust due to AGN heating. |
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Other Surveys
Members of the Centre for Astrophysics Research are also active in many other large international surveys covering the whole of the electromagnetic spectrum. These include prominent positions in all of the other UKIDSS and VISTA near-infrared surveys, large surveys with eMERLIN and LOFAR and eventually the SKA, the SCUBA-2 cosmology survey, Herschel GT programme HerMES, Methanol Multi-Beam Survey, the JCMT Spectral Legacy Survey and the Herschel Galactic Plane Survey.