%---------------------------------------------------------------------------- Some baseline numbers: Wavelength range (1-2.5 mu) => Ha: z=0.5 to 2.8. Oii z=1.7 to 5.7 Lya z=7.2 to 20 lenselet scale 0.05" -> (guess! 7kpc/" -> 300pc/lenslet) z=1 8.0 6634 L-distance 2 8.5 15733 3 7.8 kpc/" 25841 5 6.4 47593 7 5.3 10 4.3 106256 Mpc 4 hr exposure depth. 4.0e-8 Jy/arcsec^2 at 8 sigma. 2.5e-8 at 5 sigma per lenslet 0.05"x0.05": 6.3e-11 Jy/lenslet at 5 sigma. at 1.2mu 1.3e-23 erg/cm2/s/A Is this correct???? Is this really the flux limit for a point source? [Numbers in sq brackets assume the original number is per lenslet] line width of 30 km/s at z=1 => 1.2A but resolving power is 4000 => 3A => detection limit = 1.3e-23*3/0.7 = 5.5e-23 erg/s/cm2 [2.2e-20 erg/s/cm2] 20 sigma limit = 2.2e-22 erg/s/cm2 [8.8e-20 erg/s/cm2] Luminosity function of HII regions in local galaxies (Delgado & Perez, 1997, ApJS, 108, 199). Very brightnest regions are f(Halpha)>1e39 erg/s (associated with rapid star formation). Typical luminosity is 1e38, faint-end flattens at 1e37. Conversion of Halpha/OII luminosity to sfr (Kennicutt AnnRev 1998) sfr (Mo/yr) = 7.9e-42 L(Halpha) (erg/s) sfr (mo/yr) = 1.4 (+-0.4) e-41 L(OII) (erg/s) 1 Msol/yr = 5e-18 erg/s/cm2 at z=1. (based on Andy Bunker's talk) (this is realistic detection limit on 8m in 4 hours) so can detect regions with sfr = 10^-5 Msol/yr !!!! [4e-3 Msol/yr] 4x10^-5 Msol/yr !!! [1.6e-2 Msol/yr] These numbers get reduced by a factor 10 by lensing magnification...!!!! Is this plausible? Telescope diameter -> factor sqrt(9) gain on 10m factor 10 reduction in psf -> factor sqrt(100) gain so would guess a 5 sigma detection limit of 1.5e-19..... certainly much more in line with the numbers in []. Either way, its very impressive (as it should be!) Typical HII region luminosity of 1e38 erg/s in Halpha. This corresponds to a flux of 1.9e-20 at z=1 and 1.25e-21 at z=3. Assuming [] numbers, and a factor 10 magnification, this can be detectect out to almost z=3, and chemical abundance analysis is possible out to z=2. (in a 4 hour exposure) The birghtest HII regions are a factor of 10 brighter than this limit, so chemical abundance analysis is possible out to z=3 and higher redshifts. (4 hour exposure). The brightest HII regions correspond to an Halpha flux of 3.7e-21 at z=5. The OII flux is a factor of 3 lower: flux=1e-21. With a factor 10 magnification, such regions are detectable in 16 hour exposures. At z=10, the Halpha flux is 7.4e-22. Assuming equal flux in Ly alpha and a factor of 10 magnification, the required flux limit is 7.4e-21. This requires a 36 hour exposure. %-------------------------------------------------------------------------- Gravitational lenses Overview -------- Gravitational lenses are key targets for TMT. The additional magnification of the source due to the lensing effect boosts the effective performance of the telescope. Gains are made to both the brightness of the source and the effective resolution. In particular, for lensing magnifications of a factor 10, the effective diffraction limit of the telescope is reduced by a factor 3. This gives Tipi the potential of resolving individual HII regions in the target galaxy. Since the HII regions already have high contrast in their emission lines, the gain in sensitivity pushes the telescopes performance into a new regime. The combination of TMT and the gravitational lens results delivers the performance that could only be achieved by a 100m telescope. Furthermore, Tipi's multiple IFU strategy is ideally suited to this application. For example, the multiIFUs can be configured to target all of the giant arc in the cluster in a single exposure. At the same time, the central contiguous IFU can be used to target the caustic region in search for $z>5$ proto galaxies, and the smaller IFU units can be used to gather redshifts for faint arclets in order to accurately define the cluster lensing potential. These targets naturally fall into three distinct science classes: z=1-3: The epoch of galaxy formation. ------------------------------------ Most of the stars in the universe are formed at this epoch. 8-10m telescopes are allowing us to probe the global properties at this epoch, and to map the demographics of the galaxy population. However, to find out how and why galaxies are changing, we need to study the internal structure of galaxies, observing their star forming regions, their chemical abundance details and dynamics. All this will allow us to establish how and why galaxies differ so much from the present day. The magnification provided by gravitational lensing boosts the sizes of distant galaxies allowing individual HII regions to be identified. While the lenslet size of 50mas corresponds to ~300pc at z>1, the boost of gravitational lensing allows us to see in much more detail. Linear magnifications of a factor 3 (ie., factor 9 boost in flux) are typical. Such objects, eg arc289 in A2218, are clearly resolved in both dimensions, and are not so distorted that we cannot reconstruct the original galaxy morphology. Thus lensing magnification allows us to achieve 120pc per element. This resolves individual HII regions. The strategy is complementary to "field" galaxy studies because the number of targets is limited (few 100). The typical extent of such arcs is 2"x5", allowing it to be into 40x100 elements. Within each HII region, star formation can be detected at levels down 1e-6 Msol/yr and chemical abundance mapping will be possible for regions with sfr > 2e-5 Msol/yr. Every HII region in the target galaxy will be detected. The data from each HII region can be used to map out the velocity structure of the galaxy with an accuracy of ~10 km/s (after line centroiding). This will provide definitive masses for these galaxies, mapping out the M/L ratio, but also level of detail that is unprecedented in current work. Using the HII as tracer particles, we will gain the third dimension that is necessary to correctly interpret the often lumpy morphologies of distant galaxies seen in HST imaging. Currently, we cannot determine the extent to which star formation takes place in stable disks at these epoch, compared to star formation induced during galaxy encounters with minor mergers. Detailed dynamical information will probe the true nature of these distant galaxies. In addition to they use as tracer particles, we can map the size and luminosity distributions of the HII regions, providing key insight into the nature of star formation in these objects. The emission line sensitivity of Tipi is such that we will be able to measure chemical abundances for individual regions. For example, over the redshift rane 1.7 to 2.8 we can measure the whole wavelength region from OII to Halpha, providing diagnostic measured of chemical enrichment, reddening (Hbeta/Halpha) and the electron density (OII line ratio). Need s/n=5 in Halpha to measure velocity structure s/n=20 in Halpha to measure chemical abundance. [I haven't included anything about - Absorption line measures: old star and post-starburst populations. The gain over 8m will only scale with the aperture size] In the central regions of the target galaxies, the AGN accretion region will be resolved down to 100pc scales (is this comparable to the accretion disk size (?check?). Not only does this allow a clear separation to be made between star formation and AGN contributions to the galaxy's ionisation region, but it becomes possible to probe the physical region around the AGN itself. One key measurement is the determination of the central black hole mass. This will provide a vital constraint on models for the growth of black holes, and their role in defining the star formation history of the universe. Primeval Galaxies (z=5-7). ----------------- Giant galaxies begin to emerge from the dark ages at redshifts 5-7. Although such galaxies are intrinsically faint, gravitational lensing again allows us to resolve them in detail. The greater distance to these objects can be offset using systems with greater intrinsic magnification. For example the z=5 galaxy lensed by the RCS0224 cluster has a magnification of 25 and is sufficiently bright for an initial investigation to be made on an 8m telescope. Many more such galaxies will be viable targets for TMT. As with the lower redshift systems, velocity structure, dynamical masses and chemical abundance maps are all key diagnostics of how galaxies are being formed at these early epochs. The issues discussed in S1.1 apply equally here (with the limitation that Halpha is redshifted out of the observable window, and that alternative diagnostics must be used). At these redshifts, however, interstellar rest-frame UV absorption lines such as SII become redshifted into the Tipi window. These lines allow the interstellar medium to be studied in absorption against the galaxy's HII regions. These lines add a new dimension to the study of these galaxies: we can directly determine if the star formation is driving an outflow (or super-wind) out of the galaxy. The First Galaxies (z>7) ------------------------ Lensing boost enables the detection of the most distant galaxies at even higher redshift. (Add some discussion of Ellis et al work on lensed objects at z=6). Such objects can be detected through their line emission even though the continuum is for to weak. In addition to gaining from its greater aperture size, Tipi gains because the diffraction limit is matched to the size of the galaxies HII regions. In this way, the combination of telescope, gravitational lens and instrument is optimied for the detection of the first galaxies. At redshifts above 6, Lyman alpha must be used to track the objects. Although case B recombination suggests a Ly alpha:H_alpha flux ratio of 10, Lyman alpha is much more strongly subject to dust extinction. Although the metal content of these primeval is galaxies may be low, we conservatively assume that equal flux is emitted in the Halpha and Lyman alpha lines. At z=10, the most luminous HII regions can then be detected in a 36 hours exposure (assuming a magnification of 10). The highest redshifts that could be detected are limited by the accessible wavelength range to z=20. Present estimate suggest that the universe is slowly reionised over the redshift interval z=6 to 10. Such distant emission line objects provide us with the means of understanding how the universe becomes ionised. An important consideration is that the flexible IFU configuration of TIPI allows the caustic region to be mapped where the lensing effect is strongest. It is not necessary to exactly understand the gravitational potential in order to choose the target region. Mapping the Mass Distribution. ----------------------------- A key part of the Tipi design is the flexibility of the IFU assignment. Many lenselts may be observed in each observation, with the highest magnification region in the center of the clusters being observed in its entirity. As well as addressing the science goals described above, the IFU data for each lenslet stringently constrain mass distribution. Because of the available velocity information, point to point registration of images is possible using velocity and line profile information. The very accurately determines the geometry of the dark matter potential. Information which in turn improves the reconstruction of individual arcslets, and alows very accurate comparision of the baryonic and dark matter mass distibutions. With such accurate constraints on the cluster mass distribution, it is also possible to constrain the cosmological geometry using the geometric terms in the lensing equation.