Search

We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the solar system, exploring the transient optical sky, and mapping the Milky Way. LSST will be a large, wide-field ground-based system designed to obtain repeated images covering the sky visible from Cerro Pachón in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg 2 field of view, a 3.2-gigapixel camera, and six filters (ugrizy) covering the wavelength range 320-1050 nm. The project is in the construction phase and will begin regular survey operations by 2022. About 90% of the observing time will be devoted to a deep-wide-fast survey mode that will uniformly observe a 18,000 deg 2 region about 800 times (summed over all six bands) during the anticipated 10 yr of operations and will yield a co-added map to r ∼27.5. These data will result in databases including about 32 trillion observations of 20 billion galaxies and a similar number of stars, and they will serve the majority of the primary science programs. The remaining 10% of the observing time will be allocated to special projects such as Very Deep and Very Fast time domain surveys, whose details are currently under discussion. We illustrate how the LSST science drivers led to these choices of system parameters, and we describe the expected data products and their characteristics.

We present extensive photometry at ultraviolet (UV), optical, and near-infrared (NIR) wavelengths, as well as dense sampling of optical spectra, for the normal Type Ia supernova (SN Ia) 2005cf. The optical photometry, performed at eight different telescopes, shows a 1σ scatter of ≲0.03 mag after proper corrections for the instrument responses. From the well-sampled light curves, we find that SN 2005cf reached a B-band maximum at 13.63 0.02 mag, with an observed luminosity decline rate Δm 15(B) = 1.05 0.03 mag. The correlations between the decline rate and various color indexes, recalibrated on the basis of an expanded SN Ia sample, yield a consistent estimate for the host-galaxy reddening of SN 2005cf, E(B - V)host = 0.10 0.03 mag. The UV photometry was obtained with the Hubble Space Telescope and the Swift Ultraviolet/Optical Telescope, and the results match each other to within 0.1-0.2 mag. The UV light curves show similar evolution to the broadband U, with an exception in the 2000-2500 spectral range (corresponding to the F220W/uvm2 filters), where the light curve appears broader and much fainter than that on either side (likely owing to the intrinsic spectral evolution). Combining the UV data with the ground-based optical and NIR data, we establish the generic UV-optical-NIR bolometric light curve for SN 2005cf and derive the bolometric corrections in the absence of UV and/or NIR data. The overall spectral evolution of SN 2005cf is similar to that of a normal SN Ia, but with variety in the strength and profile of the main feature lines. The spectra at early times displayed strong, high-velocity (HV) features in the CaII H&K doublet and NIR triplet, which were distinctly detached from the photosphere (v 10,000 km s-1) at a velocity ranging from 20,000 to 25,000 km s -1. One interesting feature is the flat-bottomed absorption observed near 6000 in the earliest spectrum, which rapidly evolved into a triangular shape and then became a normal SiII λ6355 absorption profile at about one week before maximum brightness. This premaximum spectral evolution is perhaps due to the blending of the SiIIλ6355 at photospheric velocity and another HV absorption component (e.g., an SiII shell at a velocity 18,000 km s -1) in the outer ejecta, and may be common in other normal SNe Ia. The possible origin of the HV absorption features is briefly discussed. © 2009. The American Astronomical Society.

The recent robust and homogeneous analysis of the world's supernova distance-redshift data, together with cosmic microwave background and baryon acoustic oscillation data-provides a powerful tool for constraining cosmological models. Here we examine particular classes of scalar field, modified gravity, and phenomenological models to assess whether they are consistent with observations even when their behavior deviates from the cosmological constant ?. Some models have tension with the data, while others survive only by approaching the cosmological constant, and a couple are statistically favored over ? cold dark matter. Dark energy described by two equation-of-state parameters has considerable phase space to avoid ? and next-generation data will be required to constrain such physics, with the level of complementarity between probes varying with cosmology.

In the epoch of precise and accurate cosmology, cross-confirmation using a variety of cosmographic methods is paramount to circumvent systematic uncertainties. Owing to progenitor histories and explosion physics differing from those of Type Ia supernovae (SNeIa), Type II-plateau supernovae (SNeII-P) are unlikely to be affected by evolution in the same way. Based on a new analysis of 17 SNeII-P, and on an improved methodology, we find that SNeII-P are good standardizable candles, almost comparable to SNeIa. We derive a tight Hubble diagram with a dispersion of 10% in distance, using the simple correlation between luminosity and photospheric velocity introduced by Hamuy and Pinto. We show that the descendent method of Nugent etal. can be further simplified and that the correction for dust extinction has low statistical impact. We find that our SN sample favors, on average, a very steep dust law with total to selective extinction RV < 2. Such an extinction law has been recently inferred for many SNeIa. Our results indicate that a distance measurement can be obtained with a single spectrum of a SNII-P during the plateau phase combined with sparse photometric measurements. © 2009. The American Astronomical Society. All rights reserved.

We present spectroscopy of 15 star-forming BzK galaxies (sBzKs) with K(AB)

We present spectroscopy of 15 star-forming BzK galaxies (sBzKs) with K(AB)

We consider sterile neutrinos with rest masses ∼ 0.2 GeV and with vacuum flavor mixing angles θ2 > 10-8 for mixing with τ-neutrinos, or 10-8 < θ2 < 10-7 for mixing with muon neutrinos. Such sterile neutrinos could augment core collapse supernova shock energies by enhancing energy transport from the core to the vicinity of the shock front. The decay of these neutrinos could produce a flux of very energetic active neutrinos, detectable by future neutrino observations from galactic supernova. The relevant range of sterile neutrino masses and mixing angles can be probed in future laboratory experiments. © 2008 Elsevier B.V. All rights reserved.

We consider sterile neutrinos with rest masses ∼ 0.2 GeV and with vacuum flavor mixing angles θ2 > 10-8 for mixing with τ-neutrinos, or 10-8 < θ2 < 10-7 for mixing with muon neutrinos. Such sterile neutrinos could augment core collapse supernova shock energies by enhancing energy transport from the core to the vicinity of the shock front. The decay of these neutrinos could produce a flux of very energetic active neutrinos, detectable by future neutrino observations from galactic supernova. The relevant range of sterile neutrino masses and mixing angles can be probed in future laboratory experiments. © 2008 Elsevier B.V. All rights reserved.

We consider the prospects for testing the dark matter interpretation of the DAMA/LIBRA signal with the Super-Kamiokande experiment. The DAMA/LIBRA signal favors dark matter with low mass and high scattering cross section. We show that these characteristics imply that the scattering cross section that enters the DAMA/LIBRA event rate determines the annihilation rate probed by Super-Kamiokande. Current limits from Super-Kamiokande through-going events do not test the DAMA/LIBRA favored region. We show, however, that upcoming analyses including fully-contained events with sensitivity to dark matter masses from 5 to 10 GeV may corroborate the DAMA/LIBRA signal. We conclude by considering three specific dark matter candidates, neutralinos, WIMPless dark matter, and mirror dark matter, which illustrate the various model-dependent assumptions entering our analysis. © 2009 IOP Publishing Ltd and SISSA.

We have recently completed a 64 night spectroscopic monitoring campaign at the Lick Observatory 3 m Shane telescope with the aim of measuring the masses of the black holes in 13 nearby (z

We propose that dark matter is composed of particles that naturally have the correct thermal relic density, but have neither weak-scale masses nor weak interactions. These models emerge naturally from gauge-mediated supersymmetry breaking, where they elegantly solve the dark-matter problem. The framework accommodates single or multiple component dark matter, dark-matter masses from 10 MeV to 10 TeV, and interaction strengths from gravitational to strong. These candidates enhance many direct and indirect signals relative to weakly interacting massive particles and have qualitatively new implications for dark-matter searches and cosmological implications for colliders.

This is a report on the findings of the dark matter science working group forthe white paper on the status and future of TeV gamma-ray astronomy. The whitepaper was commissioned by the American Physical Society, and the full whitepaper can be found on astro-ph (arXiv:0810.0444). This detailed sectiondiscusses the prospects for dark matter detection with future gamma-rayexperiments, and the complementarity of gamma-ray measurements with otherindirect, direct or accelerator-based searches. We conclude that anycomprehensive search for dark matter should include gamma-ray observations,both to identify the dark matter particle (through the charac- teristics of thegamma-ray spectrum) and to measure the distribution of dark matter in galactichalos.

We discuss a new kind of astrophysical transport problem: the coherent evolution of neutrino flavor in core collapse supernovae. Solution of this problem requires a numerical approach which can simulate accurately the quantum mechanical coupling of intersecting neutrino trajectories and the associated nonlinearity which characterizes neutrino flavor conversion. We describe here the two codes developed to attack this problem. We also describe the surprising phenomena revealed by these numerical calculations. Chief among these is that the nonlinearities in the problem can engineer neutrino flavor transformation which is dramatically different to that in standard Mikheyev-Smirnov-Wolfenstein treatments. This happens even though the neutrino mass-squared differences are measured to be small, and even when neutrino self-coupling is sub-dominant. Our numerical work has revealed potential signatures which, if detected in the neutrino burst from a Galactic core collapse event, could reveal heretofore unmeasurable properties of the neutrinos, such as the mass hierarchy and vacuum mixing angle 13. © 2008 IOP Publishing Ltd.

WIMPless dark matter provides a framework in which dark matter particles with a wide range of masses naturally have the correct thermal relic density. We show that WIMPless dark matter with mass around 2-10 GeV can explain the annual modulation observed by the DAMA experiment without violating the constraints of other dark matter searches. This explanation implies distinctive and promising signals for other direct detection experiments, GLAST, and the LHC. © 2008 Elsevier B.V. All rights reserved.

The NSF has chosen the site for the Deep Underground Science and EngineeringLaboratory (DUSEL) to be in Lead, South Dakota. In fact, the state of SouthDakota has already stepped up to the plate and contributed its own funding forthe proposed lab, see http://www.sanfordlaboratoryathomestake.org/index.html.The final decision by NSF for funding the Initial Suite of Experiments forDUSEL will be made early in 2009. At that time the NSF Science Board must makea decision. Of order 200 experimentalists have already expressed an interest inperforming experiments at DUSEL. In order to assess the interest of thetheoretical community, the Center for Cosmology and Astro-Particle Physics(CCAPP) at The Ohio State University (OSU) organized a 3-day DUSEL TheoryWorkshop in Columbus, Ohio from April 4 - 6, 2008. The workshop focused on thescientific case for six proposed experiments for DUSEL: long baseline neutrinooscillations, proton decay, dark matter, astrophysical neutrinos, neutrinolessdouble beta decay and N-Nbar oscillations. The outcome of this workshop is the DUSEL Theory White paper addressing thescientific case at a level which may be useful in the decision making processfor policy makers at the NSF and in the U.S. Congress. In order to assess thephysics interest in the DUSEL project we have posted the DUSEL Theory Whitepaper on the following CCAPP link http://ccapp.osu.edu/whitepaper.html . Pleaseread the white paper and, if you are interested, use the link to show yoursupport by co-signing the white paper.

The use of Type Ia supernovae as distance indicators led to the discovery ofthe accelerating expansion of the universe a decade ago. Now that large secondgeneration surveys have significantly increased the size and quality of thehigh-redshift sample, the cosmological constraints are limited by the currentlyavailable sample of ~50 cosmologically useful nearby supernovae. The NearbySupernova Factory addresses this problem by discovering nearby supernovae andobserving their spectrophotometric time development. Our data sample includesover 2400 spectra from spectral timeseries of 185 supernovae. This talkpresents results from a portion of this sample including a Hubble diagram(relative distance vs. redshift) and a description of some analyses using thisrich dataset.

We present a new compilation of Type Ia supernovae (SNe Ia), a new data set of low-redshift nearby-Hubble-flow SNe, and new analysis procedures to work with these heterogeneous compilations. This "Union" compilation of 414 SNe Ia, which reduces to 307 SNe after selection cuts, includes the recent large samples of SNe Ia from the Supernova Legacy Survey and ESSENCE Survey, the older data sets, as well as the recently extended data set of distant supernovae observed with the Hubble Space Telescope (HST). A single, consistent, and blind analysis procedure is used for all the various SN Ia subsamples, and a new procedure is implemented that consistently weights the heterogeneous data sets and rejects outliers. We present the latest results from this Union compilation and discuss the cosmological constraints from this new compilation and its combination with other cosmological measurements (CMB and BAO). The constraint we obtain from supernovae on the dark energy density isΩΛ = 0.713-0.029+0.027(stat) -0.039+0.036(sys), for a flat, ACDM universe. Assuming a constant equation of state parameter, w, the combined constraints from SNe, BAO, and CMB give w = -0.969-0.063+0.059(stat) -0.066+0.063(sys). While our results are consistent with a cosmological constant, we obtain only relatively weak constraints on a w that varies with redshift. In particular, the current SN data do not yet significantly constrain w at z > 1. With the addition of our new nearby Hubble-flow SNe Ia, these resulting cosmological constraints are currently the tightest available. © 2008. The American Astronomical Society. All rights reserved.

Energetic young pulsars and expanding blast waves (supernova remnants, SNRs)are the most visible remains after massive stars, ending their lives, explodein core-collapse supernovae. The Fermi Gamma-Ray Space Telescope has unveiled aradio quiet pulsar located near the center of the compact synchrotron nebulainside the supernova remnant CTA 1. The pulsar, discovered through itsgamma-ray pulsations, has a period of 316.86 ms, a period derivative of 3.614 x10-13 s s-1 . Its characteristic age of 104 years is comparable to thatestimated for the SNR. It is conjectured that most unidentified Galactic gammaray sources associated with star-forming regions and SNRs are such youngpulsars.

Owing to its extremely high luminosity and long duration, supernova (SN) 2006gy radiated more energy in visual light than any other known SN. Two hypotheses to explain its high luminosity at early times - that it was powered by shock interaction with circumstellar material (CSM) as implied by its Type IIn spectrum, or that it was fueled by radioactive decay from a large mass of 56Ni synthesized in a pair-instability SN-predicted different late-time properties. Here we present observations of SN 2006gy obtained more than a year after discovery. We were unable to detect it at visual wavelengths, but clear near-infrared (IR) K′ and H-band detections show that it is still at least as luminous as the peak of a normal Type II SN. We also present spectra giving an upper limit to the late-time Ha luminosity of ≲S10 39 erg s-1. Based on the weak late-time Ha, X-ray, and radio emission, combined with the difficulty of explaining the shift to IR wavelengths, we can rule out ongoing CSM interaction as the primary late-time power source of SN 2006gy. Instead, we propose that the evolution of SN 2006gy is consistent with one of two possible scenarios: (1)apairinstability SN plus modest CSM interaction, where the radioactive decay luminosity shifts to the IR because of dust formation; or (2) an IR echo, where radiation emitted during peak luminosity heats a pre-existing dust shell at radii near 1 light year, requiring the progenitor star to have ejected another shell of ∼10 M ⊙ about 1500 yr before the SN. © 2008. The American Astronomical Society. All rights reserved.

Owing to its extremely high luminosity and long duration, supernova (SN) 2006gy radiated more energy in visual light than any other known SN. Two hypotheses to explain its high luminosity at early times - that it was powered by shock interaction with circumstellar material (CSM) as implied by its Type IIn spectrum, or that it was fueled by radioactive decay from a large mass of 56Ni synthesized in a pair-instability SN-predicted different late-time properties. Here we present observations of SN 2006gy obtained more than a year after discovery. We were unable to detect it at visual wavelengths, but clear near-infrared (IR) K′ and H-band detections show that it is still at least as luminous as the peak of a normal Type II SN. We also present spectra giving an upper limit to the late-time Ha luminosity of ≲S10 39 erg s-1. Based on the weak late-time Ha, X-ray, and radio emission, combined with the difficulty of explaining the shift to IR wavelengths, we can rule out ongoing CSM interaction as the primary late-time power source of SN 2006gy. Instead, we propose that the evolution of SN 2006gy is consistent with one of two possible scenarios: (1)apairinstability SN plus modest CSM interaction, where the radioactive decay luminosity shifts to the IR because of dust formation; or (2) an IR echo, where radiation emitted during peak luminosity heats a pre-existing dust shell at radii near 1 light year, requiring the progenitor star to have ejected another shell of ∼10 M ⊙ about 1500 yr before the SN. © 2008. The American Astronomical Society. All rights reserved.

Dark matter may be hidden, with no standard model gauge interactions. At the same time, in WIMPless models (WIMP: weakly interacting massive particles) with hidden matter masses proportional to hidden gauge couplings squared, the hidden dark matter's thermal relic density may naturally be in the right range, preserving the key quantitative virtue of WIMPs. We consider this possibility in detail. We first determine model-independent constraints on hidden sectors from big bang nucleosynthesis and the cosmic microwave background. Contrary to conventional wisdom, large hidden sectors are easily accommodated. A flavour-free version of the standard model is allowed if the hidden sector is just 30% colder than the observable sector after reheating. Alternatively, if the hidden sector contains a one-generation version of the standard model with characteristic mass scale below 1MeV, even identical reheating temperatures are allowed. We then analyse hidden sector freeze-out in detail for a concrete model, solving the Boltzmann equation numerically and explaining the results from both observable and hidden sector points of view. We find that WIMPless dark matter does indeed obtain the correct relic density for masses in the range . The upper bound results from the requirement of perturbativity, and the lower bound assumes that the observable and hidden sectors reheat to the same temperature, and is raised to the MeV scale if the hidden sector is ten times colder. WIMPless dark matter therefore generalizes the WIMP paradigm to the largest mass range possible for viable thermal relics and provides a unified framework for exploring dark matter signals across nine orders of magnitude in dark matter mass. © 2008 IOP Publishing Ltd.

The Spitzer high resolution spectra of 72 Seyfert galaxies from the 12$\mu$mGalaxy Sample are presented and discussed. The presence of starburst componentsin these galaxies can be quantified by powerful mid-IR diagnostics tools (i.e.11.25$\mu$m PAH feature equivalent width and the H$_2$ emission lineintensity), as well as the AGN dominance can be measured by specific finestructure line ratios (e.g. [NeV]/[NeII], [NeV]/[SiII], etc.). The two types ofSeyfert galaxies do not show any statistical difference in our diagnostictools. However, the Seyfert 2's showing hidden Broad Line Regions inspectro-polarimetric observations have on average an higher AGN dominance, aweaker star formation component and a warmer [60 - 25] spectral index thanthose without broad emission lines.

We measure the evolution of the correlation between black hole mass and host spheroid velocity dispersion (MBH-σ*) over the last 6 billion years, by studying three carefully selected samples of active galaxies at z = 0.57, z = 0.36 and z < 0.1. For all three samples, virial black hole masses are consistently estimated using the line dispersion of Hβ and the continuum luminosity at 5100 Å or Hα line luminosity, based on our cross calibration of the broad-line region size-luminosity relation. For the z = 0.57 sample, new stellar velocity dispersions are measured from high signal-to-noise ratio spectra obtained at the Keck Telescope, while for the two lower redshift samples they are compiled from previous works. Extending our previous result at z = 0.36, we find an offset from the local relation, suggesting that for fixed MBH, distant spheroids have on average smaller velocity dispersions than local ones. The measured offset at z = 0.57 is Δ log σ* = 0.12 ± 0.05 ± 0.06 (or Δ log MBH = 0.50 ± 0.22 ± 0.25), i.e., Δ log M BH = (3.1 ± 1.5) log (1 + z) + 0.05 ± 0.21. This is inconsistent with a tight and nonevolving universal M BH-σ* relation at the 95% CL. © 2008. The American Astronomical Society. All rights reserved.

We measure the evolution of the correlation between black hole mass and host spheroid velocity dispersion (MBH-σ*) over the last 6 billion years, by studying three carefully selected samples of active galaxies at z = 0.57, z = 0.36 and z < 0.1. For all three samples, virial black hole masses are consistently estimated using the line dispersion of Hβ and the continuum luminosity at 5100 Å or Hα line luminosity, based on our cross calibration of the broad-line region size-luminosity relation. For the z = 0.57 sample, new stellar velocity dispersions are measured from high signal-to-noise ratio spectra obtained at the Keck Telescope, while for the two lower redshift samples they are compiled from previous works. Extending our previous result at z = 0.36, we find an offset from the local relation, suggesting that for fixed MBH, distant spheroids have on average smaller velocity dispersions than local ones. The measured offset at z = 0.57 is Δ log σ* = 0.12 ± 0.05 ± 0.06 (or Δ log MBH = 0.50 ± 0.22 ± 0.25), i.e., Δ log M BH = (3.1 ± 1.5) log (1 + z) + 0.05 ± 0.21. This is inconsistent with a tight and nonevolving universal M BH-σ* relation at the 95% CL. © 2008. The American Astronomical Society. All rights reserved.

We investigate the sky distribution of z ~ 6 Lyman break galaxies selected asi'-dropouts having i' - z' > 1.45 down to z' < 26.5 in the Subaru Deep Field(SDF). We discover 37 i'-dropouts clustered in a projected comoving 21.6 x 21.6Mpc^2 region at z = 6, showing a local density excess. Carrying out follow-upspectroscopy, we identify four of them as Lyman-alpha emitters at z = 5.92,6.01, 6.03 and 6.03 (spread over a distance of 46.6 Mpc). The number density ofthe cluster itself in SDF is ~ 2.2 x 10^{-7} Mpc^{-3}, smaller than those ofprotoclusters (i.e., forming galaxy clusters) at z ~ 2-5.7. Also, the structureshows ~4-21 times larger galaxy number density than those of z ~ 6 galaxies ina general field. It has a mass of M ~ 1.5^{+1.8}_{-0.5} x 10^{15}M_sun,comparable to those of z ~ 0-5 protoclusters. Since the contamination of oursample by interlopers is estimated to be quite low, 5.9%, most of the otherunconfirmed i'-dropouts in the overdense region can be also z ~ 6 galaxies.Hence, it could be a candidate forming cluster at z ~ 6, representing aprogenitor of galaxy clusters seen in the recent-day Universe.

The first high-resolution Spitzer 1RS 9-37 μm spectra of 29 Seyfert galaxies of the 12 μm Active Galaxy Sample are presented. The spectroscopy was obtained with off-source observations, allowing excellent background subtraction and thus accurate measurements of continuum levels and strengths of weak emission lines. Several new combinations of emission-line ratios and line/continuum ratios were identified as effective diagnostics of the strength of the AGN component in these galaxies. The line ratios [Ne v]/[Ne II], [O IV]/[Ne II], already known, but also [Ne III]/[Ne II] and [Ne v]/[Si II] can be used to measure the dominance of the AGN. The equivalent width of the 11.25 μm PAH feature, like that of the 6.2 μm PAH feature, already studied, also anticorrelates with the dominance of the AGN. Our measurements indicate that the 11.25 μm PAH feature has a constant ratio with H2 S(1) irrespective of Seyfert type, approximately 10 to 1. The ratio of the 19 μm fluxes observed with the two spectrometer channels, with aperture areas differing by a factor of 4, measures the source extendedness, giving another estimate of the AGN dominance, which correlates with both the EWs of [Ne n] and PAH emission. Using the rotational transitions of H2, we estimated temperatures (200-300 K) and masses (1 -10 × 106 M⊙) for the warm molecular component. Finally, we used the ratios of the doublets of [Ne v] and of [S III] to estimate the gas electron density, which appears to be of the order of ne ∼ 103-104 cm-3 for the highly ionized component and a factor 10 lower for the intermediate- ionization gas. © 2008. The American Astronomical Society. All rights reserved.

We present our survey for optically faint variable objects using multiepoch (8-10 epochs over 2-4 years) i′-band imaging data obtained with Subaru Suprime-Cam over 0.918 deg2 in the Subaru/XMM-Newton Deep Field (SXDF). We found 1040 optically variable objects by image subtraction for all the combinations of images at different epochs. This is the first statistical sample of variable objects at depths achieved with 8-10 m class telescopes or the Hubble Space Telescope. The detection limit for variable components is i′vari ∼ 25.5 mag. These variable objects were classified into variable stars, supernovae (SNe), and active galactic nuclei (AGNs), based on the optical morphologies, magnitudes, colors, and optical-mid-infrared colors of the host objects, spatial offsets of variable components from the host objects, and light curves. Detection completeness was examined by simulating light curves for periodic and irregular variability. We detected optical variability for 36% ± 2% (51% ± 3% for a bright sample with i′ < 24.4 mag) of X-ray sources in the field. Number densities of variable objects as functions of time intervals Δt and variable component magnitudes i′vari are obtained. Number densities of variable stars, SNe, and AGNs are 120, 489, and 579 objects deg-2, respectively. Bimodal distributions of variable stars in the color-magnitude diagrams indicate that the variable star sample consists of bright (V ∼ 22 mag) blue variable stars of the halo population and faint (V ∼ 23.5 mag) red variable stars of the disk population. There are a few candidates of RR Lyrae providing a possible number density of ∼10-2 kpc-3 at a distance of >150 kpc from the Galactic center. © 2008. The American Astronomical Society. All rights reserved.

Black hole mass (MBH) is a fundamental property of active galactic nuclei (AGNs). In the distant universe, MBHis commonly estimated using the Mg II, Hβ, or Hα emission line widths and the optical/UV continuum or line luminosities as proxies for the characteristic velocity and size of the broad-line region. Although they all have a common calibration in the local universe, a number of different recipes are currently used in the literature. It is important to verify the relative accuracy and consistency of the recipes, as systematic changes could mimic evolutionary trends when comparing various samples. At z = 0.36, all three lines can be observed at optical wavelengths, providing a unique opportunity to compare different empirical recipes. We use spectra from the Keck Telescope and the Sloan Digital Sky Survey to compare MBHestimators for a sample of 19 AGNs at this redshift. We compare popular recipes available from the literature, finding that MBHestimates can differ up to 0.38 ± 0.05 dex in the mean (or 0.13 ± 0.05 dex, if the same virial coefficient is adopted). Finally, we provide a set of 30 internally self-consistent recipes for determining MBHfrom a variety of observables. The intrinsic scatter between cross-calibrated recipes is in the range 0.1-0.3 dex. This should be considered as a lower limit to the uncertainty of the MBHestimators. © 2008. The American Astronomical Society. All rights reserved.

We present results of 3-neutrino flavor evolution simulations for the neutronization burst from an O-Ne-Mg core-collapse supernova. We find that nonlinear neutrino self-coupling engineers a single spectral feature of stepwise conversion in the inverted neutrino mass hierarchy case and in the normal mass hierarchy case, a superposition of two such features corresponding to the vacuum neutrino mass-squared differences associated with solar and atmospheric neutrino oscillations. These neutrino spectral features offer a unique potential probe of the conditions in the supernova environment and may allow us to distinguish between O-Ne-Mg and Fe core-collapse supernovae.

Neutralino dark matter is well motivated, but also suffers from two shortcomings: it requires gravity-mediated supersymmetry breaking, which generically violates flavor constraints, and its thermal relic density Omega is typically too large. We propose a simple solution to both problems: neutralinos freeze-out with Omega approximately 10-100, but then decay to approximately 1 GeV gravitinos, which are simultaneously light enough to satisfy flavor constraints and heavy enough to be all of dark matter. This scenario is naturally realized in high-scale gauge-mediation models, ameliorates small scale structure problems, and implies that "cosmologically excluded" models may, in fact, be cosmologically preferred.

The two-dimensional (2D) distribution and kinematics of the molecular, ionized, and highly ionized gas in the nuclear regions of Seyfert 1 galaxies have been measured using high spatial resolution (∼0.09'') near-infrared spectroscopy from NIRSPEC with adaptive optics on the Keck telescope. Molecular hydrogen, H2, is detected in all nine Seyfert 1 galaxies and, in the majority of galaxies, has a spatially resolved flux distribution. In contrast, the narrow component of the Brγ emission has a distribution consistent with that of the K-band continuum. In general, the kinematics of the molecular hydrogen is consistent with thin disk rotation, with a velocity gradient of over 100 km s-1 measured across the central 0.5'' in three galaxies, and a similar gradient across the central 1.5'' in an additional two galaxies. The kinematics of Brγ is in agreement with the H2 rotation, except that in all four cases the central 0.5'' is either blue- or redshifted by more than 75 km s-1. The highly ionized gas, measured with the [Ca VIII] and [Si VII] coronal lines, is spatially and kinematically consistent with Brγ in the central 0.5''. In addition, the velocity dispersion of both the coronal and Bry emission is greater than that of H2 (by 1.3-2.0 times), suggesting that both originate from gas that is located closer to the nucleus than the H2 line emitting gas. Dynamical models have been fitted to the 2D H2 kinematics, taking into account the stellar mass distribution, the emission line flux distribution, and the point spread function. For NGC 3227 the modeling indicates a black hole mass of M BH = 2.0-4.0+1.0 × 107 M ⊙, and for NGC 4151 MBH = 3.0-2.2+0.75 × 107 M⊙. In NGC 7469 the best-fit model gives MBH < 5.0 × 107 M ⊙. In all three galaxies, modeling suggests a near face-on disk inclination angle, which is consistent with the unification theory of active galaxies. The direct black hole mass estimates verify that masses determined from technique of reverberation mapping are accurate to within a factor of 3 with no additional systematic errors. © 2008. The American Astronomical Society. All rights reserved.

We report the discovery of a z ∼ 9 Lyman break galaxy candidate, selected from the NICMOS Parallel Imaging Survey as a J-dropout with J 110 - H160 = 1.7. Spitzer/IRAC photometry reveals that the galaxy has a blue H160 - 3.6 μm color and a spectral break between 3.6 and 4.5 μm. We interpret this break as the Balmer break and derive a best-fit photometric redshift of z ∼ 9. We use Monte Carlo simulations to test the significance of this photometric redshift, and we show that there is a 96% probability of z ≥ 7. We estimate that the lower limit to the comoving number density of such galaxies at z ∼ 9 is ø > 3.8 × 10-6 Mpc-3. If the high redshift of this galaxy is confirmed, this will indicate that the luminous end of the rest-frame UV luminosity function has not evolved substantially from z ∼ 9 to z ∼ 3. Still, some small degeneracy remains between this z ∼ 9 model and models at z ∼ 2-3; deep optical imaging (reaching IAB ∼ 29) can rule out the lower z models. © 2008. The American Astronomical Society. All rights reserved.

We examine a phenomenon recently predicted by numerical simulations of supernova neutrino flavor evolution: the swapping of supernova nu(e) and nu(mu,tau) energy spectra below (above) energy E(C) for the normal (inverted) neutrino mass hierarchy. We present the results of large-scale numerical calculations which show that in the normal neutrino mass hierarchy case, E(C) decreases as the assumed effective 2x2 vacuum nu(e)nu(mu,tau) mixing angle (approximately theta13) is decreased. In contrast, these calculations indicate that E(C) is essentially independent of the vacuum mixing angle in the inverted neutrino mass hierarchy case. With a good neutrino signal from a future galactic supernova, the above results could be used to determine the neutrino mass hierarchy even if theta13 is too small to be measured by terrestrial neutrino oscillation experiments.

Dark matter particles need not be completely stable, and in fact they may be decaying now. We consider this possibility in the frameworks of universal extra dimensions and supersymmetry with very late decays of weakly interacting massive particles to Kaluza-Klein gravitons and gravitinos. The diffuse photon background is a sensitive probe, even for lifetimes far greater than the age of the Universe. Remarkably, both the energy spectrum and flux of the observed MeV gamma-ray excess may be simultaneously explained by decaying dark matter with MeV mass splittings. Future observations of continuum and line photon fluxes will test this explanation and may provide novel constraints on cosmological parameters.

We present a progress report on a project to derive the evolution of the volumetric supernova Type Ia rate from the Supernova Legacy Survey. Our preliminary estimate of the rate evolution divides the sample from Neill et al. into two redshift bins: 0.2 < z < 0.4, and 0.4 < z < 0.6. We extend this by adding a bin from the sample analyzed in Sullivan et al. in the range 0.6 < z < 0.75 from the same time period. We compare the derived trend with previously published rates and a supernova Type Ia production model having two components: one component associated closely with star formation and an additional component associated with host galaxy mass. Our observed trend is consistent with this model, which predicts a rising SN Ia rate out to at least z = 2. © 2007 American Institute of Physics.

We use high-resolution images obtained with the Advanced Camera for Surveys on board the Hubble Space Telescope to determine morphology, nuclear luminosity, and structural parameters of the spheroidal component for a sample of 20 Seyfert galaxies atz = 0.36. We combine these measurements with spectroscopic information from the Keck Telescope to determine the black hole mass-spheroid luminosity relation (MBH-LB), the fundamental plane (FP) of the host galaxies, and the black hole mass-spheroid velocity dispersion relation (MBH-σ). The FP is consistent with that of inactive spheroids at comparable redshifts. Assuming pure luminosity evolution, we find that the host spheroids had smaller luminosity and stellar velocity dispersion than today for a fixed MBH. The offsets correspond to Δ log LB,0 = 0.40 ± 0.11 ± 0.15 (Δlog MBH= 0.51 ± 0.14 ± 0.19) and Δloge σ = 0.13 ± 0.03 ± 0.05 (Δlog MBH = 0.54 ± 0.12 ± 0.21), respectively, for the MBH-L and M BH-σ relations (the double error bars indicate random and ystematic uncertainties, respectively). A detailed analysis of known systematic errors and selection effects shows that they cannot account for the observed offset. We conclude that the data are inconsistent with pure luminosity evolution and the existence of universal and tight scaling relations. In order to obey the three local scaling relations by z = 0, assuming no significant black hole growth, the distant spheroids have to grow their stellar mass by approximately 60% (Δ log Msph = 0.20 ± 0.14) in the next 4 billion years, while preserving their size and holding their stellar mass-to-light ratio approximately constant. The measured evolution can be expressed as MBH/Msph ∝ (1 + z) 1.5±1.0, consistent with black holes of a few × 10 8 M⊙ completing their growth before their host galaxies. Based on the disturbed morphologies of a fraction of the sample (6/20), we suggest collisional mergers with disk-dominated systems as the physical mechanism driving the evolution. © 2007. The American Astronomical Society. All rights reserved.

We develop a method to measure the strength of the absorption features in type la supernova (SN la) spectra and use it to make a quantitative comparisons between the spectra of type la supernovae at low and high redshifts. In this case study, we apply the method to 12 high-redshift (0.212 ≤ z ≤ 0.912) SNe la observed by the Supernova Cosmology Project. Through measurements of the strengths of these features and of the blueshift of the absorption minimum in Ca II H&K, we show that the spectra of the high-redshift SNe Ia are quantitatively similar to spectra of nearby SNe la (z < 0.15). One supernova in our high redshift sample, SN 2002fd at z = 0.279, is found to have spectral characteristics that are associated with peculiar SN 1991T/SN 1999aa-like supernovae. © ESO 2007.

We study the flavor evolution of a dense gas initially consisting of pure monoenergetic νe and ν̄e. Using adiabatic invariants and the special symmetry in such a system we are able to calculate the flavor evolution of the neutrino gas for the cases with slowly decreasing neutrino number densities. These calculations give new insights into the results of recent large-scale numerical simulations of neutrino flavor transformation in supernovae. For example, our calculations reveal the existence of what we term the "collective precession mode." Our analyses suggest that neutrinos which travel on intersecting trajectories subject to destructive quantum interference nevertheless can be in this mode. This mode can result in sharp transitions in the final energy-dependent neutrino survival probabilities across all trajectories, a feature seen in the numerical simulations. Moreover, this transition is qualitatively different for the normal and inverted neutrino mass hierarchies. Exploiting this difference, the neutrino signals from a future galactic supernova can potentially be used to determine the actual neutrino mass hierarchy. © 2007 The American Physical Society.

We report new follow-up spectroscopy of i′-dropout galaxies with an NB921-band depression found in the Subaru Deep Field. The NB921-depressed 1′-dropout selection method is expected to select galaxies with large equivalent-width Lyα emission over a wide redshift range, 6.0 ≲ z ≲ 6.5. Two of four observed targets show a strong emission line with a clear asymmetric profile, identified as Lyα emitters at z = 6.11 and 6.00. Their rest-frame equivalent widths are 153 Å and 114 Å, which are lower limits on the intrinsic equivalent widths. Through our spectroscopic observations (including previous ones) of NB921 -depressed i′-dropout galaxies, we identified 5 galaxies in total with a rest-frame equivalent width larger than 100 Å at 6.0 ≲ z ≲ 6.5 out of 8 photometric candidates, which suggests that the NB921 -depressed i′-dropout selection method is possibly an efficient way to search for Lyα emitters with a large Lyα equivalent width, in a wider redshift range than with usual narrow-band excess techniques. By combining these findings with our previous observational results, we infer that the fraction of broad-band selected galaxies having a rest-frame equivalent width larger than 100 Å is significantly higher at z ∼ 6 (the cosmic age of ∼1 Gyr) than that at z ∼ 3 (∼2 Gyr), being consistent with the idea that the typical stellar population of galaxies is significantly younger at z ∼ 6 than that at z ∼ 3. The NB921-depressed i′-dropout galaxies may be interesting candidates for hosts of massive, zero-metallicity Population III stars. © ESO 2007.

We monitored 13 moderate-luminosity active galactic nuclei at z = 0.36 to measure flux variability, explore feasibility of reverberation mapping, and determine uncertainties on estimating black hole mass from single-epoch data. Spectra and images were obtained with approximately weekly cadence for up to 4 months, using the Kast spectrograph on the 3 m Shane Telescope. In broad band we detect peak-to-peak variations of 9%-37% and rms variations of 2%-10%. The observed flux variability in the g′ band (rest frame 2800-4000 Å) is consistent with that in the r′ band (rest frame 4000-5200 Å), but with larger amplitude. However, after correcting for stellar light dilution using Hubble Space Telescope images, we find nuclear variability of 3%-24% (rms variation) with similar amplitudes in the g′ and r′ bands within the errors. Intrinsic flux variability of the Hβ line is also detected at the 3%-13% level, after accounting for systematic errors on the spectrophotometry. This demonstrates that a reverberation mapping campaign beyond the local universe can be carried out with a 3 m class telescope, provided that sufficiently long light curves are obtained. Finally, we compare the Hβ FWHM measured from mean spectra with that measured from single-epoch data, and find no bias but an rms scatter of 14%, mostly accounted for by the uncertainty on FWHM measurements. The propagated uncertainty on black hole mass estimates, due to the FWHM measurement errors using low S/N (10-15 pixel-1) single-epoch spectra, is 30%. © 2007. The American Astronomical Society. All rights reserved.

We monitored 13 moderate-luminosity active galactic nuclei at z = 0.36 to measure flux variability, explore feasibility of reverberation mapping, and determine uncertainties on estimating black hole mass from single-epoch data. Spectra and images were obtained with approximately weekly cadence for up to 4 months, using the Kast spectrograph on the 3 m Shane Telescope. In broad band we detect peak-to-peak variations of 9%-37% and rms variations of 2%-10%. The observed flux variability in the g′ band (rest frame 2800-4000 Å) is consistent with that in the r′ band (rest frame 4000-5200 Å), but with larger amplitude. However, after correcting for stellar light dilution using Hubble Space Telescope images, we find nuclear variability of 3%-24% (rms variation) with similar amplitudes in the g′ and r′ bands within the errors. Intrinsic flux variability of the Hβ line is also detected at the 3%-13% level, after accounting for systematic errors on the spectrophotometry. This demonstrates that a reverberation mapping campaign beyond the local universe can be carried out with a 3 m class telescope, provided that sufficiently long light curves are obtained. Finally, we compare the Hβ FWHM measured from mean spectra with that measured from single-epoch data, and find no bias but an rms scatter of 14%, mostly accounted for by the uncertainty on FWHM measurements. The propagated uncertainty on black hole mass estimates, due to the FWHM measurement errors using low S/N (10-15 pixel-1) single-epoch spectra, is 30%. © 2007. The American Astronomical Society. All rights reserved.

Table 1 in our paper, ApJ 648, 774 (2006) entitled "Intergalactic PhotonSpectra from the Far IR to the UV Lyman Limit for 0 < z < 6 and the OpticalDepth of the Universe to High Energy Gamma-Rays" had erroneous numbers for thecoefficients fitting the parametric form for the optical depth of the universeto gamma-rays. The correct values for these parameters as described in theoriginal text are given here in a corrected table for various redshifts for thebaseline model (upper row) and fast evolution (lower row) for each individualredshift. The parametric approximation is good for optical depths between 0.01and 100 and for gamma-ray energies up to ~2 TeV for all redshifts but also forenergies up to ~10 TeV for redshifts less than 1.

Table 1 in our paper, ApJ 648, 774 (2006) entitled "Intergalactic PhotonSpectra from the Far IR to the UV Lyman Limit for 0 < z < 6 and the OpticalDepth of the Universe to High Energy Gamma-Rays" had erroneous numbers for thecoefficients fitting the parametric form for the optical depth of the universeto gamma-rays. The correct values for these parameters as described in theoriginal text are given here in a corrected table for various redshifts for thebaseline model (upper row) and fast evolution (lower row) for each individualredshift. The parametric approximation is good for optical depths between 0.01and 100 and for gamma-ray energies up to ~2 TeV for all redshifts but also forenergies up to ~10 TeV for redshifts less than 1.

SDF line-emitting galaxies in four narrowband filters at low and intermediate redshifts are presented. Broadband colors, follow-up optical spectroscopy, and multiple NB filters are used to distinguish Hα, [O II], and [O III] emitters at z = 0.07-1.47 to construct their LFs. These LFs are derived down to faint magnitudes, allowing for an accurate determination of the faint-end slope. With a large (N ∼ 200-900) sample for each redshift interval, a Schechter profile is fitted to each LF. Prior to dust extinction corrections, the [O III] and [O II] LFs agree reasonably well with those of Hippelein et al. The z = 0.08 Ha LF, which reaches 2 orders of magnitude fainter than Gallego et al., is steeper by 25%. This indicates that there are more low-luminosity star-forming galaxies for z < 0.1. The faint-end slope α and Φ*, show a strong redshift evolution, while L * shows little evolution. The evolution in α indicates that low-luminosity galaxies have a stronger evolution compared to brighter ones. Integrated SFR densities are derived via Hα, [O III], and [O III] for 0.07 < z < 1.47. A steep increase in the SFR density, as a function of redshift, is seen for 0.4 < z < 0.9. For z > 1, the SFR densities are similar. The latter is consistent with previous UVand [O II] measurements. Below z < 0.4, the SFR densities are consistent with several Ha, [O II], and UV measurements, but others are a factor of 2 higher. For example, the z = 0.066-0.092 LF agrees with Jones & Bland-Hawthorn, but at z = 0.24 and 0.40, their number densities are twice as high. This discrepancy can be explained by cosmic variance. © 2007. The American Astronomical Society. All rights reserved.

We examine the utility of very high redshift Type Ia supernovae for cosmology and systematic uncertainty control. Next generation space surveys such as the Supernova/Acceleration Probe (SNAP) will obtain thousands of supernovae at z > 1.7, beyond the design redshift for which the supernovae will be exquisitely characterized. We find that any z ≳ 2 standard candles' use for cosmological parameter estimation is quite modest and subject to pitfalls; we examine gravitational lensing, redshift calibration, and contamination effects in some detail. The very high redshift supernovae - both thermonuclear and core collapse - will provide copious interesting information on star formation, environment, and evolution. However, the new observational systematics that must be faced, as well as the limited expansion of SN-parameter space afforded, does not point to high value for 1.7 < z < 3 SNe Ia in controlling evolutionary systematics relative to what SNAP can already achieve at z < 1.7. Synergy with observations from JWST and thirty meter class telescopes afford rich opportunities for advances throughout astrophysics. © 2006 Elsevier B.V. All rights reserved.

We discuss a cosmology in which cold dark matter particles decay into relativistic particles. We argue that such decays could lead naturally to a bulk viscosity in the cosmic fluid. For decay lifetimes comparable to the present Hubble age, this bulk viscosity enters the cosmic energy equation as an effective negative pressure. We investigate whether this negative pressure is of sufficient magnitude to account for the observed cosmic acceleration. We show that a single decaying species in a Λ=0, flat, dark-matter dominated cosmology can not reproduce the observed magnitude-redshift relation from Type Ia supernovae. However, a delayed bulk viscosity, possibly due to a cascade of decaying particles may be able to account for a significant fraction of the apparent cosmic acceleration. Possible candidate nonrelativistic particles for this scenario include sterile neutrinos or gauge-mediated decaying supersymmetric particles. © 2007 The American Physical Society.

Detecting heat from minor planets in the outer solar system is challenging,yet it is the most efficient means for constraining the albedos and sizes ofKuiper Belt Objects (KBOs) and their progeny, the Centaur objects. Thesephysical parameters are critical, e.g., for interpreting spectroscopic data,deriving densities from the masses of binary systems, and predictingoccultation tracks. Here we summarize Spitzer Space Telescope observations of47 KBOs and Centaurs at wavelengths near 24 and 70 microns. We interpret themeasurements using a variation of the Standard Thermal Model (STM) to derivethe physical properties (albedo and diameter) of the targets. We also summarizethe results of other efforts to measure the albedos and sizes of KBOs andCentaurs. The three or four largest KBOs appear to constitute a distinct classin terms of their albedos. From our Spitzer results, we find that the geometricalbedo of KBOs and Centaurs is correlated with perihelion distance (darkerobjects having smaller perihelia), and that the albedos of KBOs (but notCentaurs) are correlated with size (larger KBOs having higher albedos). We alsofind hints that albedo may be correlated with with visible color (forCentaurs). Interestingly, if the color correlation is real, redder Centaursappear to have higher albedos. Finally, we briefly discuss the prospects forfuture thermal observations of these primitive outer solar system objects.

We have selected 14 J-dropout Lyman break galaxy (LBG) candidates with J110 - H160 ≥ 2.5 from the NICMOS Parallel Imaging Survey. This survey consists of 135 arcmin2 of imaging in 228 independent sight lines, reaching average 5 σ sensitivities of J 110 = 25.8 and H160 = 25.6 (AB). Distinguishing these candidates from dust-reddened star-forming galaxies at z ∼ 2-3 is difficult and will require longer wavelength observations. We consider the likelihood that any J-dropout LBGs exist in this survey and find that if L*z= 9.5 is significantly brighter than L*z=6 (a factor of 4), then a few J-dropout LBGs are likely. A similar increase in luminosity has been suggested by Eyles et al. and Yan et al., but the magnitude of this increase is uncertain. © 2007. The American Astronomical Society. All rights reserved.

Minimal universal extra dimensions (mUED) is often thought to predict that the lightest Kaluza-Klein particle (LKP) is the Kaluza-Klein gauge boson B1, leading to conventional missing energy signals at colliders and weakly interacting massive particle (WIMP) dark matter. In fact, the implications of mUED are far richer: the B1, charged Higgs boson H±1, and graviton G1 are all possible LKPs, leading to many different phases with distinct signatures. Considering the complete phase diagram, we find predictions for charged or neutral particles with decay lengths of microns to tens of meters; WIMP, superWIMP, or charged relic particles; metastable particles with lifetimes of the order of or in excess of the age of the Universe; and scenarios combining two or more of these phenomena. In the cosmologically preferred region, the Higgs boson mass is between 180 and 245 GeV, the LKP mass is between 810 and 1400 GeV, and the maximal splitting between first Kaluza-Klein modes is less than 320 GeV. This region predicts a variety of exotic collider signals, such as slow charged particles, displaced vertices, tracks with nonvanishing impact parameters, track kinks, and even vanishing charged tracks, all of which provide early discovery possibilities at the Large Hadron Collider. © 2007 The American Physical Society.

Stable, hydrogen-burning, M dwarf stars make up about 75% of all stars in the Galaxy. They are extremely long-lived, and because they are much smaller in mass than the Sun (between 0.5 and 0.08 M(Sun)), their temperature and stellar luminosity are low and peaked in the red. We have re-examined what is known at present about the potential for a terrestrial planet forming within, or migrating into, the classic liquid-surface-water habitable zone close to an M dwarf star. Observations of protoplanetary disks suggest that planet-building materials are common around M dwarfs, but N-body simulations differ in their estimations of the likelihood of potentially habitable, wet planets that reside within their habitable zones, which are only about one-fifth to 1/50th of the width of that for a G star. Particularly in light of the claimed detection of the planets with masses as small as 5.5 and 7.5 M(Earth) orbiting M stars, there seems no reason to exclude the possibility of terrestrial planets. Tidally locked synchronous rotation within the narrow habitable zone does not necessarily lead to atmospheric collapse, and active stellar flaring may not be as much of an evolutionarily disadvantageous factor as has previously been supposed. We conclude that M dwarf stars may indeed be viable hosts for planets on which the origin and evolution of life can occur. A number of planetary processes such as cessation of geothermal activity or thermal and nonthermal atmospheric loss processes may limit the duration of planetary habitability to periods far shorter than the extreme lifetime of the M dwarf star. Nevertheless, it makes sense to include M dwarf stars in programs that seek to find habitable worlds and evidence of life. This paper presents the summary conclusions of an interdisciplinary workshop (http://mstars.seti.org) sponsored by the NASA Astrobiology Institute and convened at the SETI Institute.