We report on a sensitive search for redshifted H$alpha$ line-emission from three high-metallicity damped Ly$alpha$ absorbers (DLAs) at $z approx 2.4$ with the Near-infrared Integral Field Spectrometer (NIFS) on the Gemini-North telescope, assisted by
the ALTtitude conjugate Adaptive optics for the InfraRed (ALTAIR) system with a laser guide star. Within the NIFS field-of-view, $approx 3.22 times 2.92$ corresponding to $approx 25$ kpc $ times 23$ kpc at $z=2.4$, we detect no statistically significant line-emission at the expected redshifted H$alpha$ wavelengths. The measured root-mean-square noise fluctuations in $0.4$ apertures are $1-3times10^{-18}$ erg s$^{-1}$ cm$^{-2}$. Our analysis of simulated, compact, line-emitting sources yields stringent limits on the star-formation rates (SFRs) of the three DLAs, $< 2.2$~M$_{odot}$ yr$^{-1}$ ($3sigma$) for two absorbers, and $< 11$~M$_{odot}$ yr$^{-1}$ ($3sigma$) for the third, at all impact parameters within $approx 12.5$~kpc to the quasar sightline at the DLA redshift. For the third absorber, the SFR limit is $< 4.4$~M$_odot$ yr$^{-1}$ for locations away from the quasar sightline. These results demonstrate the potential of adaptive optics-assisted, integral field unit searches for galaxies associated with high-$z$ DLAs.
We present a statistical detection of 1.5 GHz radio continuum emission from a sample of faint z~4 Lyman-break galaxies (LBGs). LBGs are key tracers of the high-redshift star formation history and important sources of UV photons that ionized the inter
galactic medium in the early universe. In order to better constrain the extinction and intrinsic star formation rate (SFR) of high-redshift LBGs, we combine the latest ultradeep Karl G. Jansky Very Large Array 1.5 GHz radio image and the Hubble Space Telescope Advance Camera for Surveys (ACS) optical images in the Great Observatories Origins Deep Survey-North. We select a large sample of 1771 z~4 LBGs from the ACS catalogue using $bband$-dropout color criteria. Our LBG samples have $iband$~25-28 (AB), ~0-3 magnitudes fainter than M*_UV at z~4. In our stacked radio images, we find the LBGs to be point-like under our 2 angular resolution. We measure their mean 1.5 GHz flux by stacking the measurements on the individual objects. We achieve a statistical detection of $S_{1.5GHz}$=0.210+-0.075 uJy at ~3 sigma, first time on such a faint LBG population at z~4. The measurement takes into account the effects of source size and blending of multiple objects. The detection is visually confirmed by stacking the radio images of the LBGs, and the uncertainty is quantified with Monte Carlo simulations on the radio image. The stacked radio flux corresponds to an intrinsic SFR of 16.0+-5.7 M/yr, which is 2.8X the SFR derived from the rest-frame UV continuum luminosity. This factor of 2.8 is in excellent agreement with the extinction correction derived from the observed UV continuum spectral slope, using the local calibration of meurer99. This result supports the use of the local calibration on high-redshift LBGs for deriving the extinction correction and SFR, and also disfavors a steep reddening curve such as that of the Small Magellanic Cloud.
For some samples, it has been shown that spectra of QSOs with low redshift are bluer during their brighter phases. For the FIRST bright QSO sample, we assemble their spectra from SDSS DR7 to investigate variability between the spectra from White et a
l. (2000) and from the SDSS for a long rest-frame time-lag, up to 10 years. There are 312 radio loud QSOs and 232 radio quiet QSOs in this sample, up to $z sim 3.5$. With two-epoch variation, it is found that spectra of half of the QSOs appear redder during their brighter phases. There is no obvious difference in slope variability between sub-samples of radio quiet and radio loud QSOs. This result implies that the presence of a radio jet does not affect the slope variability on 10-year timescales. The arithmetic composite difference spectrum for variable QSOs is steep at blueward of $sim$ 2500AA. The variability for the region blueward of 2500 AA is different to that for the region redward of 2500 AA.
Using the properties of SDSS DR7 QSOs catalog from Shen et al., the Baldwin effect, its slope evolution, the underlying drive for a large sample of 35019 QSOs with reliable spectral analysis are investigated. We find that the Baldwin effect exists in
this large QSOs sample, which is almost the same in 11 different redshift bins, up to $zsim 5$. The slope is -0.238 by the BCES (civ EW depends on the continuum), -0.787 by the BCES bisector. For 11 redshift-bins, there is an increasing of the Baldwin effect slope from $zsim1.5$ to $zsim2.0$. From $zsim2.0$ to $zsim5.0$, the slope change is not clear considering their uncertainties or larger redshift bins. There is a strong correlation between the rest-frame civ EW and civ-based mbh while the relation between the civ EW and mgii-based mbh is very weak. With the correction of civ-based mbh from the civ blueshift relative to mgii, we suggest that this strong correlation is due to the bias of the civ-based mbh, with respect to that from the mgii line. Considering the mgii-based mbh, a medium strong correlation is found between the civ EW and the Eddington ratio, which implies that the Eddington ratio seems to be a better underlying physical parameter than the central black hole mass.
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,
5-sigma) for an area of 0.5*0.5 degree. 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 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*10^10 M_sun. The result matches with the observational luminosity function analysis and the semi-analytic 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.
In order to find the most extreme dust-hidden high-redshift galaxies, we select 196 extremely red objects in the Ks and IRAC bands (KIEROs, [Ks-4.5um](AB)>1.6) in the 0.06 deg^2 GOODS-N region. This selection avoids the Balmer breaks of galactic spec
tra at z<4 and picks up red galaxies with strong dust extinction. The photometric redshifts of KIEROs are between 1.5 and 5, with ~70% at z~2-4. KIEROs are very massive, with M*~10^10-10^12 Msun. They are optically faint and usually cannot be picked out by the Lyman break selection. On the other hand, the KIERO selection includes approximately half of the known millimeter and submillimeter galaxies in the GOODS-N. Stacking analyses in the radio, millimeter, and submillimeter all show that KIEROs are much more luminous than average 4.5um selected galaxies. Interestingly, the stacked fluxes for ACS-undetected KIEROs in these wavebands are 2.5-5 times larger than those for ACS-detected KIEROs. With the stacked radio fluxes and the local radio-FIR correlation, we derive mean infrared luminosities of 2-7x10^12 Lsun and mean star formation rates of 300-1200 Msun/yr for KIEROs with redshifts. We do not find evidence of a significant subpopulation of passive KIEROs. The large stellar masses and star formation rates imply that KIEROs are $z>2$ massive galaxies in rapid formation. Our results show that a large sample of dusty ultraluminous sources can be selected in this way and that a large fraction of high-redshift star formation is hidden by dust.
We present an ultradeep Ks-band image that covers 0.5*0.5 deg^2 centered on the Great Observatories Origins Deep Survey-North (GOODS-N). The image reaches a 5 sigma depth of Ks(AB) = 24.45 in the GOODS-N region, which is as deep as the GOODS-N Spitze
r Infrared Array Camera (IRAC) 3.6 mu m image. We present a new method of constructing IRAC catalogs that uses the higher spatial resolution Ks image and catalog as priors and iteratively subtracts fluxes from the IRAC images to estimate the IRAC fluxes. Our iterative method is different from the chi^2 approach adopted by other groups. We verified our results using data taken in two different epochs of observations, as well as by comparing our colors with the colors of stars and with the colors derived from model spectral energy distributions (SEDs) of galaxies at various redshifts. We make available to the community our WIRCam Ks-band image and catalog (94951 objects in 0.25 deg^2), the Interactive Data Language (IDL) pipeline used for reducing the WIRCam images, and our IRAC 3.6 to 8.0 mu m catalog (16950 objects in 0.06 deg^2 at 3.6 mu m). With this improved Ks and IRAC catalog and a large spectroscopic sample from our previous work, we study the color-magnitude and color-color diagrams of galaxies. We compare the effectiveness of using Ks and IRAC colors to select active galactic nuclei (AGNs) and galaxies at various redshifts. We also study a color selection of z = 0.65--1.2 galaxies using the Ks, 3.6 mu m, and 4.5 mu m bands.
GOODS 850-5 is a hyperluminous radio-faint submillimeter source in the GOODS-N. Although it is generally agreed that GOODS 850-5 is at a high redshift z>~4, its exact redshift is unknown. While its stellar SED suggests z~6, its radio/FIR SED suggests
a lower redshift of z~4. To better constrain its stellar SED and redshift, we carried out nano-Jansky sensitivity ultradeep NIR observations between 1.2 and 2.1 um with the HST 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 um bands its spectral slope is >3x that of an ERO, and the flux ratio between the two bands is >8x 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* ~ 10^11.5 Msun) of reddened old stars at z~6, coexisting with an even more extinguished violent ~2400-4400 Msun/yr 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.
The second moment of the H$beta$ emission line is calculated for 329 narrow line Seyfert 1 galaxies (NLS1s) selected from the Sloan Digital Sky Survey (SDSS), which is used to calculate the central supermassive black hole (SMBHs) mass of each. We fin
d that the second moment depends strongly on the broader component of the H$beta$ line profile. We find that for the NLS1s requiring two Gaussians to fit the H$beta$ line the mean value of the SMBH mass from the H$beta$ second moment is larger by about 0.50 dex than that from the full width at half maximum (FWHM). Using the gas velocity dispersion of the core/narrow component of oiii $lambda$ 5007 to estimate the stellar velocity dispersion, $sigma_{*}$, the new mass makes NLS1s fall very close to the $mbh - sigma_{*}$ relation for normal AGNs. By using $sigma_{*}$ measured directly from SDSS spectra with a simple stellar population synthesis method, we find that for NLS1s with mass lower than $10^7 msun$, they fall only marginally below the $mbh - sigma_{*}$ relation considering the large scatter in the mass calculation.
Type II AGNs with polarimetric broad emission line provided strong evidence for the orientation-based unified model for AGNs. We want to investigate whether the polarimetric broad emission line in type II AGNs can be used to calculate their central s
upermassive black hole (SMBH) masses, like that for type I AGNs. We collected 12 type II AGNs with polarimetric broad emission line width from the literatures, and calculated their central black hole masses from the polarimetric broad line width and the isotropic oiii luminosity. We also calculate the mass from stellar velocity dispersion, $sigma_*$, with the $mbh-sigma_*$ relation.We find that: (1) the black hole masses derived from the polarimetric broad line width is averagely larger than that from the $mbh- sigma_*$ relation by about 0.6 dex, (2) If these type II AGNs follow $mbh-sigma_*$ relation, we find that the random velocity cant not be omitted and is comparable with the BLRs Keplerian velocity. It is consistent with the scenery of large outflow from the accretion disk suggested by Yong et al.
