Highest Redshift Bin Research Articles

Weak-lensing calibration of a stellar mass-based mass proxy for redMaPPer and Voronoi Tessellation clusters in SDSS Stripe 82

We present the first weak lensing calibration of $\mu_{\star}$, a new galaxy cluster mass proxy corresponding to the total stellar mass of red and blue members, in two cluster samples selected from the SDSS Stripe 82 data: 230 redMaPPer clusters at redshift $0.1\leq z<0.33$ and 136 Voronoi Tessellation (VT) clusters at $0.1 \leq z < 0.6$. We use the CS82 shear catalog and stack the clusters in $\mu_{\star}$ bins to measure a mass-observable power law relation. For redMaPPer clusters we obtain $M_0 = (1.77 \pm 0.36) \times 10^{14}h^{-1} M_{\odot}$, $\alpha = 1.74 \pm 0.62$. For VT clusters, we find $M_0 = (4.31 \pm 0.89) \times 10^{14}h^{-1} M_{\odot}$, $\alpha = 0.59 \pm 0.54$ and $M_0 = (3.67 \pm 0.56) \times 10^{14}h^{-1} M_{\odot}$, $\alpha = 0.68 \pm 0.49$ for a low and a high redshift bin, respectively. Our results are consistent, internally and with the literature, indicating that our method can be applied to any cluster finding algorithm. In particular, we recommend that $\mu_{\star}$ be used as the mass proxy for VT clusters. Catalogs including $\mu_{\star}$ measurements will enable its use in studies of galaxy evolution in clusters and cluster cosmology.

The redshift evolution of major merger triggering of luminous AGNs: a slight enhancement at z ∼ 2

Active galactic nuclei (AGN), particularly the most luminous AGN, are commonly assumed to be triggered through major mergers, however observational evidence for this scenario is mixed. To investigate any influence of galaxy mergers on AGN triggering and luminosities through cosmic time, we present a sample of 106 luminous X-ray selected type 1 AGN from the COSMOS survey. These AGN occupy a large redshift range (0.5 < z < 2.2) and two orders of magnitude in X-ray luminosity ($\sim$10$^{43}$ - 10$^{45}$ erg s$^{-1}$). AGN hosts are carefully mass and redshift matched to 486 control galaxies. A novel technique for identifying and quantifying merger features in galaxies is developed, subtracting GALFIT galaxy models and quantifying the residuals. Comparison to visual classification confirms this measure reliably picks out disturbance features in galaxies. No enhancement of merger features with increasing AGN luminosity is found with this metric, or by visual inspection. We analyse the redshift evolution of AGN associated with galaxy mergers and find no merger enhancement in lower redshift bins. Contrarily, in the highest redshift bin (z$\sim$2) AGN are $\sim$4 times more likely to be in galaxies exhibiting evidence of morphological disturbance compared to control galaxies, at 99% confidence level ($\sim$2.4$\sigma$) from visual inspection. Since only $\sim$15% of these AGN are found to be in morphologically disturbed galaxies, it is implied that major mergers at high redshift make a noticeable but subdominant contribution to AGN fuelling. At low redshifts other processes dominate and mergers become a less significant triggering mechanism.

Constraining the relative velocity effect using the Baryon Oscillation Spectroscopic Survey

We analyse the power spectrum of the Baryon Oscillation Spectroscopic Survey (BOSS), Data Release 12 (DR12) to constrain the relative velocity effect, which represents a potential systematic for measurements of the Baryon Acoustic Oscillation (BAO) scale. The relative velocity effect is sourced by the different evolution of baryon and cold dark matter perturbations before decoupling. Our power spectrum model includes all $1$-loop redshift-space terms corresponding to $v_{\rm bc}$ parameterised by the bias parameter $b_{v^2}$. We also include the linear terms proportional to the relative density, $\delta_{\rm bc}$, and relative velocity dispersion, $\theta_{\rm bc}$, which we parameterise with the bias parameters $b^{\rm bc}_{\delta}$ and $b^{\rm bc}_{\theta}$. Our data does not support a detection of the relative velocity effect in any of these parameters. Combining the low and high redshift bins of BOSS, we find limits of $b_{v^2} = 0.012 \pm 0.015\;(\pm 0.031)$, $b^{\rm bc}_{\delta} = -1.0 \pm 2.5\;(\pm 6.2)$ and $b^{\rm bc}_{\theta} = -114 \pm 55\;(\pm 175)$ with $68\%$ ($95\%$) confidence levels. These constraints restrict the potential systematic shift in $D_A(z)$, $H(z)$ and $f\sigma_8$, due to the relative velocity, to $1\%$, $0.8\%$ and $2\%$, respectively. Given the current uncertainties on the BAO measurements of BOSS these shifts correspond to $0.53\sigma$, $0.5\sigma$ and $0.22\sigma$ for $D_A(z)$, $H(z)$ and $f\sigma_8$, respectively.

The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: baryon acoustic oscillations in the Fourier space

We analyse the Baryon Acoustic Oscillation (BAO) signal of the final Baryon Oscillation Spectroscopic Survey (BOSS) data release (DR12). Our analysis is performed in Fourier-space, using the power spectrum monopole and quadrupole. The dataset includes $1\,198\,006$ galaxies over the redshift range $0.2 < z < 0.75$. We divide this dataset into three (overlapping) redshift bins with the effective redshifts $\zeff = 0.38$, $0.51$ and $0.61$. We demonstrate the reliability of our analysis pipeline using N-body simulations as well as $\sim 1000$ MultiDark-Patchy mock catalogues, which mimic the BOSS-DR12 target selection. We apply density field reconstruction to enhance the BAO signal-to-noise ratio. By including the power spectrum quadrupole we can separate the line-of-sight and angular modes, which allows us to constrain the angular diameter distance $D_A(z)$ and the Hubble parameter $H(z)$ separately. We obtain two independent $1.6\%$ and $1.5\%$ constraints on $D_A(z)$ and $2.9\%$ and $2.3\%$ constraints on $H(z)$ for the low ($\zeff=0.38$) and high ($\zeff=0.61$) redshift bin, respectively. We obtain two independent $1\%$ and $0.9\%$ constraints on the angular averaged distance $D_V(z)$, when ignoring the Alcock-Paczynski effect. The detection significance of the BAO signal is of the order of $8\sigma$ (post-reconstruction) for each of the three redshift bins. Our results are in good agreement with the Planck prediction within $\Lambda$CDM. This paper is part of a set that analyses the final galaxy clustering dataset from BOSS. The measurements and likelihoods presented here are combined with others in~\citet{Alam2016} to produce the final cosmological constraints from BOSS.

CONSTRAINING AGN FEEDBACK IN MASSIVE ELLIPTICALS WITH SOUTH POLE TELESCOPE MEASUREMENTS OF THE THERMAL SUNYAEV–ZEL’DOVICH EFFECT

ABSTRACT Energetic feedback due to active galactic nuclei (AGNs) is likely to play an important role in the observed anti-hierarchical trend in the evolution of galaxies, and yet the energy injected into the circumgalactic medium by this process is largely unknown. One promising approach to constrain this feedback is through measurements of spectral distortions in the cosmic microwave background due to the thermal Sunyaev–Zeldovich (tSZ) effect, whose magnitude is directly proportional to the energy input by AGNs. With current instruments, making such measurements requires stacking large numbers of objects to increase signal-to-noise. While one possible target for such stacks is AGNs themselves, these are relatively scarce sources that contain contaminating emission that complicates tSZ measurements. Here we adopt an alternative approach and co-add South Pole Telescope SZ (SPT-SZ) survey data around a large set of massive quiescent elliptical galaxies at z &ge; 0.5 ?> , which are much more numerous and less contaminated than active AGNs, yet are subject to the same feedback processes from the AGNs they hosted in the past. We use data from the Blanco Cosmology Survey and VISTA Hemisphere Survey to create a large catalog of galaxies split up into two redshift bins: one with 3394 galaxies at 0.5 &le; z &le; 1.0 ?> and one with 924 galaxies at 1.0 &le; z &le; 1.5 , ?> with typical stellar masses of 1.5 &times; 10 11 M &CircleDot; . ?> We then co-add the emission around these galaxies, resulting in a measured tSZ signal at 2.2 &sgr; ?> significance for the lower redshift bin and a contaminating signal at 1.1 &sgr; ?> for the higher redshift bin. To remove contamination due to dust emission, we use SPT-SZ source counts to model a contaminant source population in both the SPT-SZ bands and Planck high-frequency bands for a subset of 937 galaxies in the low-redshift bin and 240 galaxies in the high-redshift bin. This increases our detection to 3.6 &sgr; ?> for low redshifts and 0.9 &sgr; ?> for high redshifts. We find the mean angularly integrated Compton-y values to be 2.2 &minus; 0.7 &plus; 0.9 &times; 10 &minus; 7 ?> Mpc2 for low redshifts and 1.7 &minus; 1.8 &plus; 2.2 &times; 10 &minus; 7 ?> Mpc2 for high redshifts, corresponding to total thermal energies of 7.6 &minus; 2.3 &plus; 3.0 &times; 10 60 ?> erg and 6.0 &minus; 6.3 &plus; 7.7 &times; 10 60 ?> erg, respectively. These numbers are higher than expected from simple theoretical models that do not include AGN feedback, and serve as constraints that can be applied to current simulations of massive galaxy formation.

The bulge-disc decomposition of AGN host galaxies

We present the results from a study of the morphologies of moderate luminosity X-ray selected AGN host galaxies in comparison to a carefully mass-matched control sample at 0.5 < z < 3 in the CANDELS GOODS-S field. We apply a multi-wavelength morphological decomposition analysis to these two samples and report on the differences between the morphologies as fitted from single Sersic and multiple Sersic models, and models which include an additional nuclear point-source component. Thus, we are able to compare the widely adopted single Sersic fits from previous studies to the results from a full morphological decomposition, and address the issue of how biased the inferred properties of AGN hosts are by a potential nuclear contribution from the AGN itself. We find that the AGN hosts are mixed systems which have higher bulge fractions than the control sample in our highest redshift bins at the >99.7% confidence level, according to all model fits even those which adopt a point-source component. This serves to alleviate concerns that previous, purely single Sersic, analyses of AGN hosts could have been spuriously biased towards higher bulge fractions. This dataset allows us to further probe the physical nature of these point-source components; we find no strong correlation between the point-source component and AGN activity, and that these point-source components are best modelled physically by nuclear starbursts. Our analysis of the bulge and disk fractions of these AGN hosts in comparison to a mass-matched control sample reveals a similar morphological evolutionary track for both the active and non-active populations, providing further evidence in favour of a model where AGN activity is triggered by secular processes.

HerMES: SPIRE emission from radio-selected active galactic nuclei★

We examine the rest-frame far-infrared emission from powerful radio sources with 1.4GHz luminosity densities of 25<=log(L_1.4/WHz^-1)<=26.5 in the extragalactic Spitzer First Look Survey field. We combine Herschel/SPIRE flux densities with Spitzer/IRAC and MIPS infrared data to obtain total (8-1000um) infrared luminosities for these radio sources. We separate our sources into a moderate, 0.4<z<0.9, and a high, 1.2<z<3.0, redshift sub-sample and we use Spitzer observations of a z<0.1 3CRR sample as a local comparison. By comparison to numbers from the SKA Simulated Skies we find that our moderate redshift sample is complete and our high redshift sample is 14per cent complete. We constrain the ranges of mean star formation rates (SFRs) to be 3.4-4.2, 18-41 and 80-581Msun/yr for the local, moderate and high redshift samples respectively. Hence, we observe an increase in the mean SFR with increasing redshift which we can parameterise as ~(1+z)^Q, where Q=4.2+/-0.8. However we observe no trends of mean SFR with radio luminosity within the moderate or high redshift bins. We estimate that radio-loud AGN in the high redshift sample contribute 0.1-0.5per cent to the total SFR density at that epoch. Hence, if all luminous starbursts host radio-loud AGN we infer a radio-loud phase duty cycle of 0.001-0.005.

ERRATUM: “SPACE DENSITY OF OPTICALLY SELECTED TYPE 2 QUASARS” (2008, AJ, 136, 2373)

Figure 12 of the paper Space Density of Optically Selected Type 2 Quasars compares the obscured quasar fractions derived in our work with those of other studies. Unfortunately, some of the points from these other studies were shown incorrectly. Specifically, the results from X-ray data—Hasinger (2004; open circles) and Ueda et al. (2003; open squares)—which we had taken from Figure 16 of Hopkins et al. (2006), were affected by a luminosity conversion error, in the sense that the displayed luminosities for these data were too high by ~1 dex. With this erratum, we correct this problem and update the figure. The new version (Figure 12) shows more recent results from Hasinger (2008), in lieu of the Hasinger (2004) data points. These are based on data in the redshift range z = 0.2-3.2 (open circles) in that work. The best linear fit to these data (black dashed line) is consistent with that derived for the redshift slice z = 0.4-0.8, which overlaps with the highest redshift bin in our study, and is higher than that derived for redshifts smaller than 0.4 (corresponding to a shift of ~0.7 dex in luminosity). Figure 12 also shows estimates of the obscured quasar fraction derived from the ratio of IR to bolometric luminosities of an AGN sample at redshift z ~ 1 (Treister et al. 2008; filled triangles). Because the obscured quasar fractions derived from our analysis (colored arrows) are strict lower limits, there was already a hint in the previous version of Figure 12 that at high quasar luminosities, we find higher obscured quasar fractions than X-ray surveys. The correction and updates of Figure 12 strengthen this conclusion. At face value, our derived obscured quasar fractions are consistent with those from IR data (Treister et al. 2008; filled triangles). However, we find that they are significantly higher than those derived from X-ray surveys at , especially those from the recent analysis by Hasinger (2008). This comparison strongly suggests that optical selection successfully identifies a population of luminous obscured quasars that are missed by X-ray selection.

Investigating the far-IR/radio correlation of star-forming Galaxies toz= 3

In order to examine the far-IR/radio correlation at high redshift we have studied the Spitzer 70um/far-infrared (far-IR) properties of sub-mJy radio sources from the 13^H XMM-Newton/Chandra Deep Field by redshift and galaxy type: active galactic nucleus (AGN) or star forming galaxy (SFG). We directly detect 70um counterparts (at >3sigma significance) for 22.5% (92/408) of the radio sources, while for the rest we perform stacking analysis by redshift and galaxy type. For the sources detected at 70um we find that the median and scatter of the observed flux density ratio, q70, are similar to previous results in the literature, but with a slight decrease in q70 towards higher redshifts. Of the radio sources detected at 70um 8/92 were already classified as AGN, but two of which maybe SFGs. For the stacked sources we obtain a detection for the SFGs at every redshift bin which implies they have mean flux densities a factor ~5 below the original 70um detection limit. For the stacked AGN we obtain a detection only in our highest redshift bin (1<~z<~5) where we may be sampling hot dust associated with the AGN at rest-frame 12-35um. The combined observed mean value of q70 for the SFGs (detected and non-detected at 70um) decreases gradually with redshift, consistent with tracks derived from empirical spectral energy distributions (SEDs) of local SFGs. Upon closer inspection and when comparing with tracks of appropriate luminosity, the values of q70 broadly agree at low redshift. However, at z~1, the observed q70 (for ULIRGs) is 2sigma below the value seen for local ULIRGs tracks, implying a difference in the SED between local and z~1 ULIRGs. At higher redshifts, the convergence of the tracks and the higher uncertainties in q70 do not allow us to determine if such a difference persists.

Bright highzSnIa: A challenge forΛCDM

It has recently been pointed out by Kowalski et. al. [Astrophys. J. 686, 749 (2008).] that there is ``an unexpected brightness of the SnIa data at $z&gt;1$.'' We quantify this statement by constructing a new statistic which is applicable directly on the type Ia supernova (SnIa) distance moduli. This statistic is designed to pick up systematic brightness trends of SnIa data points with respect to a best fit cosmological model at high redshifts. It is based on binning the normalized differences between the SnIa distance moduli and the corresponding best fit values in the context of a specific cosmological model (e.g. $\ensuremath{\Lambda}\mathrm{CDM}$). These differences are normalized by the standard errors of the observed distance moduli. We then focus on the highest redshift bin and extend its size toward lower redshifts until the binned normalized difference (BND) changes sign (crosses 0) at a redshift ${z}_{c}$ (bin size ${N}_{c}$). The bin size ${N}_{c}$ of this crossing (the statistical variable) is then compared with the corresponding crossing bin size ${N}_{mc}$ for Monte Carlo data realizations based on the best fit model. We find that the crossing bin size ${N}_{c}$ obtained from the Union08 and Gold06 data with respect to the best fit $\ensuremath{\Lambda}\mathrm{CDM}$ model is anomalously large compared to ${N}_{mc}$ of the corresponding Monte Carlo data sets obtained from the best fit $\ensuremath{\Lambda}\mathrm{CDM}$ in each case. In particular, only 2.2% of the Monte Carlo $\ensuremath{\Lambda}\mathrm{CDM}$ data sets are consistent with the Gold06 value of ${N}_{c}$ while the corresponding probability for the Union08 value of ${N}_{c}$ is 5.3%. Thus, according to this statistic, the probability that the high redshift brightness bias of the Union08 and Gold06 data sets is realized in the context of a $({w}_{0},{w}_{1})=(\ensuremath{-}1,0)$ model ($\ensuremath{\Lambda}\mathrm{CDM}$ cosmology) is less than 6%. The corresponding realization probability in the context of a $({w}_{0},{w}_{1})=(\ensuremath{-}1.4,2)$ model is more than 30% for both the Union08 and the Gold06 data sets indicating a much better consistency for this model with respect to the BND statistic.

REDSHIFT EVOLUTION IN THE IRON ABUNDANCE OF THE INTRACLUSTER MEDIUM

Clusters of galaxies provide a closed box within which one can determine the chemical evolution of the gaseous baryons with cosmic time. We studied this metallicity evolution in the hot X-ray emitting baryons through an analysis of XMM-Newton observations of 29 galaxy clusters in the redshift range 0.3 < z < 1.3. Taken alone, this data set does not show evidence for significant evolution. However, when we also include a comparable sample of 115 clusters observed with Chandra (Maughan et al. 2008) and a lower redshift sample of 70 clusters observed with XMM at z < 0.3 (Snowden et al. 2008), there is definitive evidence for a decrease in the metallicity. This decrease is approximately a factor of two from z = 0 to z \approx 1, over which we find a least-squares best-fit line Z(z) / Z_{\odot} = (0.46 \pm 0.05) - (0.38 \pm 0.03)z. The greatest uncertainty in the evolution comes from poorly constrained metallicities in the highest redshift bin.

AEGIS: Infrared Spectral Energy Distributions of MIPS 70 μm-selected Sources

We present 0.5-160 μm spectral energy distributions (SEDs) of galaxies, detected at 70 μm with the Multiband Imaging Photometer for Spitzer (MIPS), using broadband imaging data from Spitzer and ground-based telescopes. Spectroscopic redshifts, in the range 0.2 ≤ z ≤ 1.5, have been measured as part of the Deep Extragalactic Evolutionary Probe 2 (DEEP2) project. On the basis of the SEDs, we explore the nature and physical properties of the sources. Using the optical spectra, we derive Hβ and [O II]-based star formation rates (SFRs) that are 10-100 times lower than SFR estimates based on IR and radio. The median offset in SFR between optical and IR is reduced by a factor of ~3 when we apply a typical extinction correction. We investigate mid- to far-infrared correlations for low-redshift (>0.5) and high-redshift (0.5 < z < 1.2) bins. Using this unique far-infrared-selected sample, we derive an empirical mid- to far-infrared relationship that can be used to estimate the infrared energy budget of galaxies in the high-redshift universe. Our sample can be used as a template to translate far-infrared luminosities into bolometric luminosities for high-redshift objects.

The Ultraviolet Galaxy Luminosity Function from GALEX Data: Color-Dependent Evolution at Low Redshift

We present measurements of the far-UV (FUV; 1530 Å) and near-UV (NUV; 2310 Å) galaxy luminosity functions (LFs) at low redshift (z ≤ 0.2) from Galaxy Evolution Explorer observations matched to the Two-Degree Field (2dF) Galaxy Redshift Survey. We split our FUV and NUV samples into two UV - bJ color bins and two redshift bins. As observed at optical wavelengths, the local LF of the bluest galaxies tend to have steeper faint-end slopes and fainter characteristic magnitudes M* than the reddest subsamples. We find evidence for color-dependent evolution at very low redshift in both bands, with bright blue galaxies becoming dominant in the highest redshift bin. The evolution of the total LF is consistent with an ~0.3 mag brightening between z ~ 0 and 0.13, in agreement with the first analysis of deeper GALEX fields probing adjacent and higher redshifts.

Evolution of the colour-radius and morphology-radius relations in SDSS galaxy clusters

We have investigated the redshift evolution of the colour--cluster-centric-radius relation and the morphology--cluster-centric-radius relation in three redshift bins, $0.02\leq z\leq 0.14$, $0.14< z\leq 0.20$, and $0.20< z\leq 0.30$ using a homogeneous sample of 736 galaxy clusters selected from the Sloan Digital Sky Survey. Both the relations are well-defined in all the redshift bins; the fraction of blue/late-type galaxies increases toward outside of clusters.Blue/late-type galaxy fractions are found to decrease with decreasing redshift at any cluster-centric radius. The trend is consistent with the Butcher-Oemler effect and the morphological Butcher-Oemlereffect. In addition, we find that colour (spectral) evolution is almost completed by $z\sim0.2$, whereas morphological evolution continues to the present day. The colour-radius relation is smooth inall the redshift bins, while the morphology--radius relation has a break only in the highest redshift bin. It is also found thatfractions of blue-late type galaxies decreases mostly between the highest and the intermediate redshift bins, while fractions of red-late type galaxies continuously decreases with decreasing redshift through all the redshift bins. These results are consistent with the interpretation that the timescale of the colour (spectral) evolution is shorter than that of the morphological evolution. It is suggested that red-late type galaxies in the middle of the transformation are observed as passive spiral galaxies.

A European Southern Observatory Very Large Telescope Survey of Near‐Infrared (Z≤ 25) Selected Galaxies at Redshifts 4.5 &lt;z&lt; 6: Constraining the Cosmic Star Formation Rate near the Reionization Epoch

We present the results of a Very Large Telescope (VLT) and Hubble Space Telescope imaging survey aimed at the identification of 4.5 4.5 galaxies. The resulting integral surface density of the ZAB 4.5 is in the range 0.13-0.44 arcmin-2, and that in the highest redshift bin 5 < z ? 6 is between 0.07 and 0.13 arcmin-2. In the two HDFs, we identify 25 galaxies at IAB ? 27.2 in the range 4.5 ? z < 5 and 16 at 5 ? z ? 6, corresponding to surface densities of 3.1 and 2 arcmin-2, respectively. We show that the observed ZAB < 25 UV luminosity density (LD) appears to drop by about 1 order of magnitude from z 3 to 6. However, if we apply a threshold to obtain an absolute magnitude-limited sample, the UV LD is roughly constant up to z 6. We finally show that recent semianalytic hierarchical models for galaxy formation, while predicting a nearly constant total UV LD up to z 6, underpredict the observed UV LD at ZAB ? 25 and overpredict the IAB ? 27.2 one. This behavior can be understood in terms of a poor match to the slope of the UV luminosity function.