32715941
THE TAIWAN ECDFS NEAR-INFRARED SURVEY: VERY BRIGHT END OF THE LUMINOSITY FUNCTION AT z > 7
The primary goal of the Taiwan ECDFS Near-Infrared Survey (TENIS) is to find well-screened galaxy candidates at z > 7 (z' dropout) in the Extended Chandra Deep Field-South (ECDFS). To this end, TENIS provides relatively deep J and Ks data (~25.3 ABmag, 5σ) for an area of 0.5 × 0.5 deg. Leveraged with existing data at mid-infrared to optical wavelengths, this allows us to screen for the most luminous high-z objects, which are rare and thus require a survey over a large field to be found. We introduce new color selection criteria to select a z > 7 sample with minimal contaminations from low-z galaxies and Galactic cool stars; to reduce confusion in the relatively low angular resolution Infrared Array Camera (IRAC) images, we introduce a novel deconvolution method to measure the IRAC fluxes of individual sources. Illustrating perhaps the effectiveness at which we screen out interlopers, we find only one z > 7 candidate, TENIS-ZD1. The candidate has a weighted z phot of 7.8, and its colors and luminosity indicate a young (45M years old) starburst galaxy with a stellar mass of 3.2 × 1010 M ☉. The result matches with the observational luminosity function analysis and the semianalytic simulation result based on the Millennium Simulations, which may over predict the volume density for high-z massive galaxies. The existence of TENIS-ZD1, if confirmed spectroscopically to be at z > 7, therefore poses a challenge to current theoretical models for how so much mass can accumulate in a galaxy at such a high redshift.
73576245
Submillimeter Sources behind the Massive Lensing Clusters A370 and A2390
We report 850 μm Submillimeter Array (SMA) observations of four gravitationally lensed submillimeter galaxies (SMGs), A370-2, A2390-1, A2390-3, and A2390-4, which were originally discovered with the Submillimeter Common-User Bolometer Array (SCUBA). Our SMA detection of A370-2 with a submillimeter flux of 7.95 ± 0.60 mJy unambiguously identifies the counterparts to this source at optical and radio wavelengths. A2390-1 is an ultraluminous infrared galaxy with a submillimeter flux of 5.55 ± 0.92 mJy and a redshift of 1.8 ± 0.2 computed from submillimeter/radio flux ratio analysis. We resolve A2390-3 into two components, A2390-3a and A2390-3b, with fluxes of 3.15 ± 0.63 mJy and 1.92 ± 0.60 mJy, respectively. The structure of the system could be consistent with morphological distortion by gravitational lensing. The lack of counterparts in the optical and infrared indicates a heavily dust-enshrouded nature, and a non-detection in the radio implies that these two sources probably lie at z > 4.7, which would make them among the most distant SMGs known to date. Our non-detection of A2390-4 suggests either that there are multiple fainter submillimeter sources within the SCUBA beam or that the SCUBA detection may have been false. Our precise positions allow us to determine accurate amplifications and fluxes for all of our detected sources. Our new results give a shallower power-law fit (–1.10) to the faint-end 850 μm cumulative number counts than previous work. We emphasize the need for high-resolution observations of single dish detected SMGs in order to measure accurately the faint end of the 850 μm counts.
17191883
ULTRADEEP NEAR-INFRARED OBSERVATIONS OF GOODS 850-5*, **
GOODS 850-5 is a hyperluminous radio-faint submillimeter source in the Great Observatories Origins Deep Survey-North. Although it is generally agreed that GOODS 850-5 is at a high redshift, z 4, its exact redshift is unknown. While its stellar spectral energy distribution (SED) suggests z ~ 6, its radio/far-IR (FIR) SED suggests a lower redshift of z ~ 4. To better constrain its stellar SED and redshift, we carried out nano-Jansky sensitivity ultradeep near-IR (NIR) observations between 1.2 and 2.1 μm with the Hubble Space Telescope and the 8 m Subaru Telescope. Even with such great depths we did not detect GOODS 850-5, and the results show that it is an extremely curious source. Between the Ks and 3.6 μm bands, its spectral slope is greater than 3 times that of an extremely red object, and the flux ratio between the two bands is greater than 8 times that of Lyman breaks. It is quite challenging to explain this unusually red color without a Lyman break (which would imply z > 17). It requires a large amount (M ~ 1011.5 M ☉) of reddened old stars at z ~ 6, coexisting with an even more extinguished violent ~2400-4400 M ☉ yr–1 starburst, which does not have any associated detectable rest-frame UV radiation. We discuss the discrepancy between the NIR and radio/FIR photometric redshifts. We conclude that GOODS 850-5 is at least at z > 4 and is more likely at z 6. We describe the unusual properties of GOODS 850-5, including its SED and formation history, and we discuss the implications of such massive z > 6 galaxies.
8377768
Near-infrared Survey of the GOODS-North Field: Search for Luminous Galaxy Candidates at z 6.5
We present near-infrared (NIR; J and K_s) survey of the Great Observatories Origins Deep Survey-North (GOODS-N) field. The publicly available imaging data were obtained using the MOIRCS instrument on the 8.2 m Subaru and the WIRCam instrument on the 3.6 m Canada-France-Hawaii Telescope (CFHT). These observations fulfill a serious wavelength gap in the GOODS-N data, i.e., lack of deep NIR observations. We combine the Subaru/MOIRCS and CFHT/WIRCam archival data to generate deep J- and K_s-band images, covering the full GOODS-N field (~169 arcmin^2) to an AB magnitude limit of ~25 mag (3σ). We applied z_850-band dropout color selection criteria, using the NIR data generated here. We have identified two possible Lyman break galaxy (LBG) candidates at z ≳ 6.5 with J ≲ 24.5. The first candidate is a likely LBG at z ≃ 6.5 based on a weak spectral feature tentatively identified as Lyα line in the deep Keck/DEIMOS spectrum, while the second candidate is a possible LBG at z ≃ 7 based on its photometric redshift. These z 850-dropout objects, if confirmed, are among the brightest such candidates found so far. At z ≳ 6.5, their star formation rate is estimated as 100-200 M_☉ yr^(–1). If they continue to form stars at this rate, they assemble a stellar mass of ~5 × 10^(10) M_☉ after about 400 million years, becoming the progenitors of massive galaxies observed at z ≃ 5. We study the implication of the z 850-band dropout candidates discovered here, in constraining the bright end of the luminosity function and understanding the nature of high-redshift galaxies.
117142035
Correlation between Global Parameters of Galaxies
Recently Disney et al. (2008) found a striking correlation among the five basic parameters that govern the galactic dynamics: R50, R90, Lr, Md, and MHI . They suggested that this is in conflict with the LCDM model, which predicts the hierarchical formation of cosmic structures from bottom up. In light of the importance of the issue, we performed a similar analysis on global parameters of galaxies with a significantly larger database and two additional parameters, LJ and RJ, of the near-infrared J band. We used databases from the Arecibo Legacy Fast Arecibo L-band Feed Array Survey for the atomic gas properties, the Sloan Digital Sky Survey for the optical properties, and the Two Micron All Sky Survey for the near-infrared properties, of the galaxies. We conducted principal component analysis (PCA) to find relations among these observational variables and confirmed that the five parameters in the work of Disney et al. are indeed correlated. The first principal component dominates the correlations among the five parameters and can explain 86% of the variation in the data. When color (g - i) is included, the first component still dominates and the color forms a second principal component that is almost independent of other parameters. The overall trend in our near-infrared PCA is very similar, except that color (i - J) seems even more decoupled from all other parameters. The dominance of the first principal component suggests that the structure of galaxies is governed by a single physical parameter. This confirms the observational results in Disney et al. However, based on the importance of the baryon physics in galaxy formation, we are not convinced that the hierarchical structure formation scenario and the notion of cold dark matter are necessarily flawed.
118328393
Clustering Properties of BzK-selected Galaxies in GOODS-N: Environmental Quenching and Triggering of Star Formation at z ~ 2
Using a sample of BzK-selected galaxies at z ~ 2 identified from the CFHT/WIRCAM near-infrared survey of GOODS-North, we discuss the relation between star formation rate (SFR), specific star formation rate (SSFR), and stellar mass (M *), and the clustering of galaxies as a function of these parameters. For star-forming galaxies (sBzKs), the UV-based SFR, corrected for extinction, scales with the stellar mass as SFR∝M α * with α = 0.74 ± 0.20 down to M * ~ 109 M ☉, indicating a weak dependence on the stellar mass of the SFR efficiency, namely, SSFR. We also measure the angular correlation function and hence infer the correlation length for sBzK galaxies as a function of M *, SFR, and SSFR, as well as K-band apparent magnitude. We show that passive galaxies (pBzKs) are more strongly clustered than sBzK galaxies at a given stellar mass, mirroring the color-density relation seen at lower redshifts. We also find that the correlation length of sBzK galaxies ranges from 4 to 20 h –1 Mpc, being a strong function of MK , M *, and SFR. On the other hand, the clustering dependence on SSFR changes abruptly at 2 × 10–9 yr–1, which is the typical value for "main-sequence" star-forming galaxies at z ~ 2. We show that the correlation length reaches a minimum at this characteristic value, and is larger for galaxies with both smaller and larger SSFRs; a dichotomy that is only marginally implied from the predictions of the semi-analytical models. Our results suggest that there are two types of environmental effects at work at z ~ 2. Stronger clustering for relatively quiescent galaxies implies that the environment has started to play a role in quenching star formation. At the same time, stronger clustering for galaxies with elevated SSFRs ("starbursts") might be attributed to an increased efficiency for galaxy interactions and mergers in dense environments.
119115457
Light dark matter in NMSSM and implication on Higgs phenomenology
For the experimental search of neutralino dark matter, it is important to know its allowed mass and scattering cross section with the nucleon. In order to figure out how light a neutralino dark matter can be predicted in low energy supersymmetry, we scan over the parameter space of the NMSSM (next-to-minimal supersymmetric model), assuming all the relevant soft mass parameters to be below TeV scale. We find that in the parameter space allowed by current experiments the neutralino dark matter can be as light as a few GeV and its scattering rate off the nucleon can reach the sensitivity of XENON100 and CoGeNT. As a result, a sizable parameter space is excluded by the current XENON100 and CoGeNT data (the plausible CoGeNT dark matter signal can also be explained). The future 6000 kg-days exposure of XENON100 will further explore (but cannot completely cover) the remained parameter space. Moreover, we find that in such a light dark matter scenario a light CP-even or CP-odd Higgs boson must be present to satisfy the measured dark matter relic density. Consequently, the SM-like Higgs boson h(SM) may decay predominantly into a pair of light Higgs bosons or a pair of neutralinos so that the conventional decays like h(SM) -> gamma gamma is much suppressed. (C) 2011 Elsevier B.V. All rights reserved.
118791439
Reactor Neutrino Experiments: $\theta_{13}$ and Beyond
We review the current-generation short-baseline reactor neutrino experiments that have firmly established the third neutrino mixing angle $\theta_{13}$ to be non-zero. The relative large value of $\theta_{13}$ (around 9$^\circ$) has opened many new and exciting opportunities for future neutrino experiments. Daya Bay experiment with the first measurement of $\Delta m^2_{ee}$ is aiming for a precision measurement of this atmospheric mass-squared splitting with a comparable precision as $\Delta m^2_{\mu\mu}$ from accelerator muon neutrino experiments. JUNO, a next-generation reactor neutrino experiment, is targeting to determine the neutrino mass hierarchy with medium baselines ($\sim$50 km). Beside these {\color{black} opportunities enabled by the large $\theta_{13}$}, the current-generation (Daya Bay, Double Chooz, and RENO) and the next-generation (JUNO, RENO-50, and PROSPECT) reactor experiments, with their unprecedented statistics, are also leading the precision era of the 3-flavor neutrino oscillation physics as well as constraining new physics beyond the neutrino Standard Model.
115397124
omega phi STATES IN CHIRAL QUARK MODEL
The omega phi states with spin S = 0, 1 and 2 are dynamically studied in a chiral SU(3) quark model by solving the resonating group method (RCM) equation. It is found that the interactions of omega phi systems are attractive, while no omega phi bound state or resonance state is obtained due to the insufficiency of the strength of omega phi attractions.
119244677
Target mass monitoring and instrumentation in the Daya Bay antineutrino detectors
The Daya Bay experiment measures sin 22θ13 using functionally identical antineutrino detectors located at distances of 300 to 2000 meters from the Daya Bay nuclear power complex. Each detector consists of three nested fluid volumes surrounded by photomultiplier tubes. These volumes are coupled to overflow tanks on top of the detector to allow for thermal expansion of the liquid. Antineutrinos are detected through the inverse beta decay reaction on the proton-rich scintillator target. A precise and continuous measurement of the detector's central target mass is achieved by monitoring the the fluid level in the overflow tanks with cameras and ultrasonic and capacitive sensors. In addition, the monitoring system records detector temperature and levelness at multiple positions. This monitoring information allows the precise determination of the detectors' effective number of target protons during data taking. We present the design, calibration, installation and in-situ tests of the Daya Bay real-time antineutrino detector monitoring sensors and readout electronics.
119115506
High-precision measurement of atmospheric mass-squared splitting with T2K and NOvA
A precise measurement of the atmospheric mass-squared splitting |\Delta m^2_{\mu\mu}| is crucial to establish the three-flavor paradigm and to constrain the neutrino mass models. In addition, a precise value of |\Delta m^2_{\mu\mu}| will significantly enhance the hierarchy reach of future medium-baseline reactor experiments like JUNO and RENO-50. In this work, we explore the precision in |\Delta m^2_{\mu\mu}| that will be available after the full runs of T2K and NOvA. We find that the combined data will be able to improve the precision in |\Delta m^2_{\mu\mu}| to sub-percent level for maximal 2-3 mixing. Depending on the true value of \sin^2\theta_{23} in the currently-allowed 3 sigma range, the precision in |\Delta m^2_{\mu\mu}| will vary from 0.87% to 1.24%. We further demonstrate that this is a robust measurement as it remains almost unaffected by the present uncertainties in \theta_{13}, \delta_{CP}, the choice of mass hierarchy, and the systematic errors.