Rubin-LSST

Abstract:

The Large Synoptic Survey Telescope (LSST) is a proposed ground based telescope that will perform a comprehensive astronomical survey by imaging the entire visible sky in a continuous series of short exposures. Four special purpose rafts, mounted at the corners of the LSST science camera, contain wavefront sensors and guide sensors. Wavefront measurements are accomplished using curvature sensing, in which the spatial intensity distribution of stars is measured at equal distances on either side of focus by CCD detectors. The four Corner Rafts also each hold two guide sensors. The guide sensors monitor the locations of bright stars to provide feedback that controls and maintains the tracking of the telescope during an exposure. The baseline sensor for the guider is a Hybrid Visible Silicon hybrid-CMOS detector. We present here a conceptual mechanical and electrical design for the LSST Corner Rafts that meets the requirements imposed by the camera structure, and the precision of both the wavefront reconstruction and the tracking. We find that a single design can accommodate two guide sensors and one split-plane wavefront sensor integrated into the four corner locations in the camera. © 2010 SPIE.

Abstract:

We present observations of early-type galaxies with laser guide star adaptive optics (LGS AO) obtained at Gemini North telescope using the NIFS integral field unit (IFU). We employ an innovative technique where the focus compensation due to the changing distance to the sodium layer is made 'open loop', allowing the extended galaxy nucleus to be used only for tip-tilt correction. The purpose of these observations is to determine high spatial resolution stellar kinematics within the nuclei of these galaxies to determine the masses of the super-massive black holes. The resulting data have spatial resolution of 0.2" FWHM or better. This is sufficient to positively constrain the presence of the central black hole in even low-mass early-type galaxies, suggesting that larger samples of such objects could be observed with this technique in the future. The open-loop focus correction technique is a supported queue-observing mode at Gemini, significantly extending the sky coverage in particular for faint, extended guide sources. We also provide preliminary results from tests combining tip/tilt correction from the Gemini peripheral guider with on-axis LGS. The current test system demonstrates feasibility of this mode, providing about a factor 2-3 improvement over natural seeing. With planned upgrades to the peripheral wave-front sensor, we hope to provide close to 100% sky coverage with low Strehl corrections, or 'improved seeing', significantly increasing flux concentration for deep field and extended object studies. © 2010 SPIE.

Abstract:

We present a derivation of the star formation rate per comoving volume of quasar host galaxies, derived from stacking analyses of far-infrared to mm-wave photometry of quasars with redshifts 0 < z < 6 and absolute I-band magnitudes -22 > IAB > -32 We use the science demonstration observations of the first ∼ 16 deg2 from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) in which there are 240 quasars from the Sloan Digital Sky Survey (SDSS) and a further 171 from the 2dF-SDSS LRG and QSO (2SLAQ) survey. We supplement this data with a compilation of data from IRAS, ISO, Spitzer, SCUBA and MAMBO. H-ATLAS alone statistically detects the quasars in its survey area at > 5σ at 250, 350 and 500 μ m. From the compilation as a whole we find striking evidence of downsizing in quasar host galaxy formation: low-luminosity quasars with absolute magnitudes in the range -22 > IAB > -24 have a comoving star formation rate (derived from 100 μ m rest-frame luminosities) peaking between redshifts of 1 and 2, while high-luminosity quasars with IAB < -26 have a maximum contribution to the star formation density at z ∼ 3. The volume-averaged star formation rate of -22 > IAB > -24 quasars evolves as (1 + z)2.3±0.7 at z < 2, but the evolution at higher luminosities is much faster reaching (1 + z) 10±1 at -26 > IAB > -28. We tentatively interpret this as a combination of a declining major merger rate with time and gas consumption reducing fuel for both black hole accretion and star formation. © 2010 ESO.

Abstract:

We present Herschel-PACS observations of rest-frame mid-infrared and far-infrared spectral line emissions from two lensed, ultraluminous infrared galaxies at high redshift: MIPS J142824.0+352619 (MIPS J1428), a starburst-dominated system at z = 1.3, and IRAS F10214+4724 (F10214), a source at z = 2.3 hosting both star-formation and a luminous AGN. We have detected [OI]63μm and [OIII]52μm in MIPS J1428, and tentatively [O III]52μm in F10214. Together with the recent ZEUS-CSO [CII]158μm detection in MIPS J1428 we can for the first time combine [OI], [CII] and far-IR (FIR) continuum measurements for PDR modeling of an ultra-luminous (LIR ≥ 10 12 L⊙) star forming galaxy at the peak epoch of cosmic star formation. We find that MIPS J1428, contrary to average local ULIRGs, does not show a deficit in [OI] relative to FIR. The combination of far-UV flux G0 and gas density n (derived from the PDR models), as well as the star formation efficiency (derived from CO and FIR) is similar to normal or starburst galaxies, despite the high infrared luminosity of this system. In contrast, F10214 has stringent upper limits on [O IV] and [S III], and an [O III]/FIR ratio at least an order of magnitude lower than local starbursts or AGN, similar to local ULIRGs. © ESO 2010.