Subject: MCAO Science Cases Date: Mon, 16 Jun 2003 15:57:48 -0200 From: "Dimitri Alexei Gadotti" To: laerte@astro.iag.usp.br, geminiaspen@lna.br Ola' a todos! Seguindo a sugestao do Laerte, escrevo em termos dos Science Cases alguns dos itens relativos `a proposta que enviei na minha 1a mensagem. Antes, porem, tenho alguns comentarios sobre o que tem sido pensado com relacao `a resolucao espacial dos futuros estudos de galaxias em alto z. Reparei que a ideia gira em torno de se ter, com GLAO, resolucao igual a cerca de 0.3", que nao e' tao boa assim, mas por campos realmente grandes (11' ou maiores). No meu entender, com esta resolucao, os "very fuzzy blobs" de fato serao nada mais do que os "slightly less fuzzy blobs", e a ciencia (com relacao `a formacao de bojos e discos, por exemplo) a se fazer com estes dados continuara' "fuzzy". Com MCAO, os planos sao de se ter resolucao da ordem de 0.05" por campos de ate cerca de 2'. Notem que isso ocorre para condicoes medianas de seeing, o que significa que, mesmo com nossa minuscula fracao de tempo de telescopio, temos condicoes de propor observacoes com essas restricoes, sem correr um grande risco de jamais ter as observacoes concluidas. Um abraco, Dimitri. PS: O (rapido) Science Case segue abaixo. Ainda ha' a questao: e' possivel termos um analogo do Hubble Deep Field em L (3.3 um)? ----------------------------------------------------------------------------------- > Title > PI + collaborators and institution > Abstract To obtain very deep restband red optical and near-infrared images of galaxies at z ~ 1 at a spatial resolution of 0.05 arcsec. At K band this corresponds to J (at rest) imaging with unprecedent spatial resolution. Taken for a sufficiently large number of galaxies, these images will help settle on a firmer observational basis the formation of disk and bulges in spirals, the formation of elliptical galaxies and the evolution of the stellar populations in these systems. > Background Science The information we have now on the origin of the Hubble sequence and the different galactic luminous components (spheroid and disk) are based on either restband UV-optical images with excellent spatial resolution, or near-infrared images with poorer (~ 0.4 arcsec) quality. On the one hand, short wavelenght images are not a faithful source for understanding the structure of galaxies since they represent the less numerous young stars; and, on the other hand, images with poor resolution can not tell us nothing about the structure of galaxies with angular sizes as small as a few arcsec. Is based on these shaking grounds that important questions are answered nowadays. High spatial resolution at long wavelenghts allow us, e.g., to definitely answer questions as: "Are these fuzzy blobs disks or spheroids? Are they part of a larger system or are they galaxies themselves? How often galaxies host bars at these redshifts?". A true knowledge of the processes responsible for the formation of bulges and disks, elliptical galaxies, how the stellar populations evolve in these different components at these early stages, and, finally, details on the role played by dark matter haloes, can only result in putting together excellent image quality and deep near-infrared imaging. > Proposed observations (As many as possible) deep fields of 2 x 2 arcmin in J, H and K at image quality of ~ 0.05 arcsec. It can be HDF-N and S for instance. > Instrument requirements (field, spatial and spectral resolution, > wavelength coverage) 2 x 2 arcmin field; 0.05 arcsec resolution; J, H and K bands > Sensitivity requirements As it is now. The 1.5 mag raise in sensitivity from MCAO would give better statistics, confidence levels and a better sampling at outer radii. > Target density Around 50 z~1 galaxies per field (based on FIRES experience, see AJ122,2205). > Time requirements Around 7 hours per field per filter, plus small overheads. > Guide star availability Normal. Maybe laser stars are crucial for image quality? > Advantages over AO (try to quantify) > Could this program be done with classical AO field of view > (10-30";) ? No, the number of observed galaxies would be too small for good statistics. > Is this program enabled by MCAO ? In what sense ? Yes, since it is essential to have excellent image quality through the whole field. > Does this program need a very uniform image quality ? Yes. > Is this program benefiting from the gain in angular > resolution or from the gain in sensitivity (or both) ? Both. A higher sensitity will enable to probe the outer parts of disks, for instance. > Complementarity with other future facilities (ALMA, NGST, ...) Studies can be done at longer wavelenghts and pushing to higher redshifts.