CanariCam Science


An brief overview of science with CanariCam

The text of the talk "SPANISH EXPLOITATION OF CANARICAM: Opening new windows for Spanish astrophysics" presented at the " Science with the GTC meeting" (Granada, Spain) on February 6-8th 2002
 
 

The IRAS/ISO legacy

IRAS and ISO pointed mid-infrared astronomy in a new direction, opening a completely new window to the Universe and finding many new and unexpected types of object. ISO and IRAS have posed whole new sets of challenging questions for science.

Click here for a slide show reviewing some of the big issues in mid-infrared astronomy post-ISO.
 
 

Making the best use of CanariCam

What are CanariCam's strengths for mid-Infrared science, and how will these influence science programmes? Click here for a slide show reviewing how CanariCam can be used in extragalactic science.
 
 

CanariCam on GTC: the resolution advantage to go beyond IRAS and ISO

Both IRAS and ISO were small telescopes with correspondingly low angular resolution. ISO was a 60-cm telescope compared to the 10.4-m of the GTC. This means that CanariCam can attain an angular resolution 17 times greater than ISO. The difference is similar to that between the HST and an earthbound telescope with atmospheric seeing of about 1 arcsecond. In fact, if image improvement techniques work, as they should, a resolution around 0.1 arcseconds should be possible with CanariCam, making its advantage over ISO even greater. In crowded or confused fields the additional resolution of CanariCam will be vital.
 
 

Science with CC-PolCC-Pol will open up a whole range of science projects that have previously been impossible for the following reasons:

Click here to look at some of the options for cutting edge science with CC-Pol.
 
 

The CanariCam Science Team (CCST)

The CanariCam Science Team (CCST) was formed to use the 12 nights of Guaranteed Time awarded to CanariCam for science projects to be carried out jointly by UF and Spanish astronomers. Three fields of scientific excellence have been defined, and each will receive four nights of guaranteed time with the GTC+CanariCam combination. The Science Team will consist of Spanish and UF scientists in roughly equal numbers.  Some indication of the Science Team structure is indicated below, although details of the CCST organization are still in the process of being established.

The areas of scientific excellence that have been selected and some of the most interesting problems within them are:

This area focusses on brown dwarfs and planets. CanariCam offers the possibility of direct imaging of Jupiter-sized planets around nearby stars due to the very high resolution that is possible and the instrument's coronagraphic capability, combined with the large gain in contrast between the star and the planet afforded by observing in the mid-infrared. In the visible the parent star is many orders of magnitude brighter than a planet around it that shines only by reflected light. In the mid-infrared, though, the planet has its own emission that is close to the peak of the black body curve, while a star is well past the peak of its own black body curve. By observing in the mid-infrared the contrast between a star and an orbiting planet is greatly increased, and planets may be detected directly. For a typical Main Sequence star at 25 pc with a Jovian planet of 10% of the primary's diameter and a Neptunian planet of 3% the primary diameter the system would have the following characteristics in the visible : At 10 microns the contrast for a Jovian planet at 5 AU from the primary is 105 . That is, we gain 3 orders of magnitude in contrast. At 25 microns the contrast is 102 and the detection of Jupiter-type planets should become much easier, particularly with coronagraphy.
 
 
Primary
Jupiter 
5 AU
Jupiter 
30 AU
Neptune 
30 AU
Magnitude (V)
6.8
26.8
30.8
33.6
Separation primary
-
0".2
1".2
1".2
Contrast
-
108
4x109
5x1010

 
 
 
 
 
 
 
 
 

Between planets and stars there are the brown dwarfs. These are "stars" that are not large enough to initiate nuclear fusion in their centres, but are sufficiently massive to still be warm from gravitational compression. Brown dwarfs are of particular interest because they may account for some of the "missing mass" which forms a dynamically significant but as yet unseen halo for our Milky Way Galaxy - and other galaxies as well. CanariCam will be able to search for different types of brown dwarfs to determine whether they are important in the gravitational dynamics of the Milky Way. CanariCam can provide constraints on the properties of dark, massive objects in the halo of the Galaxy, to search young stellar clusters for recently formed brown dwarfs, and to look for "super-planets" - with masses between 0.1% and 1% that of the Sun - orbiting nearby stars.

 
Planets are thought to form in dusty circumstellar disks, and so the exploration of disks contributes fundamentally to a broader understanding of the origin and evolution of our own and other planetary systems. One expects the detailed structure (e.g., size, shape, and density) of a very young disk to markedly influence how and where planets are formed there. On the other hand, the detailed structure of an older, more evolved disk should bear traces of its history and of any planets that may have already formed, or are in the process of forming. In one widely accepted scenario, gas and dust accrete directly onto the central forming protostar during the initial phase of cloud collapse. Eventually, the primary accretion shifts to a circumstellar disk, which accumulates enough mass (~0.3 of the stellar mass) to become gravitationally unstable, form spiral arms, and transport angular momentum outward. At this point, the disk is the main source of matter accreting onto the star. As the protocloud becomes depleted, accretion onto the disk ceases, and both the disk mass and the accretion rate onto the star decrease. Stellar winds, UV radiation, planetesimal/planet formation, and residual accretion completely erode the primordial disk, which is replaced by a more diffuse "debris disk" that is continually replenished with comet dust and collisional fragments.

The mid-IR radiation that we see from circumstellar disks is generally thermal radiation from dust heated by starlight and/or (for the densest, youngest disks) viscous accretion. We expect a monotonic falloff of the dust temperature with distance from the star. Usually in astrophysical environments the dust we see in the mid-IR is hotter than about 100 K, temperatures that are attained within a hundred or so AU of an A star. This scale is comparable to the size of our solar system, so the mid-IR is a particularly useful probe of circumstellar regions relevant to the exploration of the origin and evolution of planets. The diffraction limits of CanariCam on the GTC are 0.2 arcsec and 0.4 arcsec at 10 and 20 mm, respectively. Thus, for a star at 20 pc, we can resolve details in disks that have scale sizes of the order of 5-10 AU, clearly useful for our exploration of planetary disks.

CanariCam will provide mid-IR images that support that will bear on the relevant evolutionary time scales and the detailed structure of circumstellar disks and the planet-forming process in them. These images will be at the highest achievable angular resolutions (0.25 arcsec at 10 mm) and span several passbands in the 8 - 25 mm spectral region. Among the key elements of a program to observe these disks are to:

Explore the relative roles of circumstellar disks and envelopes in producing the excess mid-IR emission from Herbig Ae/Be stars;

Define the temperature and density structure of pms and ms disks; Delineate the affects of planetary or stellar companions on the structure of pms and ms disks; Determine the properties of disks as a function of stellar age. In addition, CanariCam can compare low resolution spectra of the circumstellar material with spectra of emission from comets in our own solar system in order to compare the physical conditions in the primitive solar system to those in the debris disks. The nature of IR-luminous galaxies is still open to some debate. Two models have been invoked: heating of dust by super-massive black holes in the galactic nuclei; or by large populations of massive stars. Due to the very high extinction, visible spectroscopy is an unreliable guide to the conditions in the galaxies. Spectroscopy with CanariCam will allow line ratios, particularly of the 12.8 microns [NeII], 9.0 microns [ArIII], and 10.5 microns [S IV] lines to be calculated. The ionisation potentials of Ne0 (22 eV), Ar+ (28 eV) and S++ (35eV) are ideally suited to the calculation of the hardness of the radiation field, an important diagnostic of the exciting mechanism. By observing IR-luminous galaxies at a wide range of redshifts to distances corresponding to >90% of the age of the Universe (z > 5), CanariCam will have an excellent capability of studying the properties and evolution of ULGs, and the relationship between these galaxies and AGN discovered by other techniques. The presence of such systems would imply that the epoch of galaxy formation occurred very early in the history of the Universe. With CanariCam we will be able to characterise the evolution of ULGs in space-time, and test the hypotheses linking IR galaxies and quasars. CanariCam will also have the capability of probing the heavily extinguished nuclei of the brightest and closest of these objects with spectroscopy to establish the excitation, ionising source, and abundance of heavy elements in different redshift regimes. These spectroscopic observations will help determine the physical conditions in the optically-obscured interiors of these galaxies, thereby distinguishing between stellar and non-thermal processes as the ultimate source of their luminosity.

An unsolved puzzle in theories of active galactic nuclei is the connection between the accretion and energy generation in the central parsec and the processes on larger scales in the host galaxy. Over the past few years, based on mid-infrared studies of Seyfert galaxies, it has been found that the host galaxies of Seyfert 2 nuclei have substantially elevated rates of star formation compared to the hosts of Seyfert 1 nuclei and field galaxies. This behaviour is in violation of the simplest form of unified theory for Seyfert nuclei, which would require all isotropic characteristics of type 1 and type 2 to be the same. The presence of a huge maximum of emission (typically peaking at 60 microns) is a good tracer of starburst activity. With IRAS and ISO their poor spatial resolution has only allowed one to say that this emission-component is present, without knowing where within the galaxy it is emitted. With CanariCam it would be possible to resolve this emission within the galaxy and use it as a tracer of the history of starburst activity. We should remember that the resolution of CanariCam will be at least a factor of 2 better at 8 microns than the 0.4 arcsecond seeing expected with the telescope in the visible and, at 20 microns, the resolution will be comparable with the best visible seeing. Even below 8 microns we can expect to surpass the best spatial resolution possible in the visible without the use of adaptive optics. Mid-infrared observations can tell us much about extragalactic star formation in galaxies of all kinds, particularly when one takes into account the fact the spatial resolution of the 10-m telescope will be around two orders of magnitude better than ISO's.

 Scientific Exploitation of CanariCam

The Science Team has the task of focussing the efforts within each area  and developing it into a science programme that will obtain the maximum benefit from the available time. It is anticipated that many other science projects will spin-off from this effort. There is a wide range of exciting CanariCam science that may be carried out.

Calibrating CanariCam

The quality of scientific data is heavily dependent on the quality of its calibration. CanariCam has a calibration team that is working on astronomical spectrophotopolarimetric calibration. The aim is to establish an all-sky network of stars suitable for calibrating all of the observing modes of CanariCam.

Back to the Main CanariCam Page.

Latest update: February 19th 2002