arXiv subjects

Huanyuan Shan

Publications and source records attributed to Huanyuan Shan.

At least 91 records · Page 5Linked to original sources

arXiv2020

Pre-selection of the Candidate Fields for Deep Imaging of the Epoch of Reionization with SKA1-Low

The Square Kilometre Array (SKA) will be the first low-frequency instrument with the capability to directly image the structures of the Epoch of Reionization (EoR). Indeed, deep imaging of the EoR over 5 targeted fields of 20 square degrees each has been selected as the highest priority science objective for SKA1. Aiming at preparing for this highly challenging observation, we perform an extensive pre-selection of the `quietest' and `cleanest' candidate fields in the southern sky to be suited for deep imaging of the EoR using existing catalogs and observations over a broad frequency range. The candidate fields should meet a number of strict criteria to avoid contaminations from foreground structures and sources. The candidate fields should also exhibit both the lowest average surface brightness and smallest variance to ensure uniformity and high quality deep imaging over the fields. Our selection eventually yields a sample of 7 `ideal' fields of 20 square degrees in the southern sky that could be targeted for deep imaging of the EoR. Finally, these selected fields are convolved with the synthesized beam of SKA1-low stations to ensure that the effect of sidelobes from the far field bright sources is also weak.

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arXiv2020

Separating the Intrinsic Alignment Signal and the Lensing Signal using Self-Calibration in Photo-z Surveys with KiDS450 and KV450 Data

To reach the full potential for the next generation of weak lensing surveys, it is necessary to mitigate the contamination of intrinsic alignments (IA) of galaxies in the observed cosmic shear signal. The self calibration (SC) of intrinsic alignments provides an independent method to measure the IA signal from the survey data and the photometric redshift information. It operates differently from the marginalization method based on IA modeling. In this work, we present the first application of SC to the KiDS450 data and the KV450 data, to split directly the intrinsic shape - galaxy density (Ig) correlation signal and the gravitational shear - galaxy density (Gg) correlation signal, using the information from photometric redshift (photo-z). We achieved a clear separation of the two signals and performed several validation tests. Our measured signals are found to be in general agreement with the KiDS450 cosmic shear best-fit cosmology, for both lensing and IA measurements. For KV450, we use partial (high-z) data, and our lensing measurements are also in good agreement with KV450 cosmic shear best-fit, however, our IA signal suggests a larger IA amplitude. We discussed the impact of photo-z quality on IA detection and several other potential systematic biases. Finally, we discuss the potential application of the information extracted for both the lensing signal and the IA signal in future surveys.

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arXiv2020

The BUFFALO HST Survey

The Beyond Ultra-deep Frontier Fields and Legacy Observations (BUFFALO) is a 101 orbit + 101 parallel Cycle 25 Hubble Space Telescope Treasury program taking data from 2018-2020. BUFFALO will expand existing coverage of the Hubble Frontier Fields (HFF) in WFC3/IR F105W, F125W, and F160W and ACS/WFC F606W and F814W around each of the six HFF clusters and flanking fields. This additional area has not been observed by HST but is already covered by deep multi-wavelength datasets, including Spitzer and Chandra. As with the original HFF program, BUFFALO is designed to take advantage of gravitational lensing from massive clusters to simultaneously find high-redshift galaxies which would otherwise lie below HST detection limits and model foreground clusters to study properties of dark matter and galaxy assembly. The expanded area will provide a first opportunity to study both cosmic variance at high redshift and galaxy assembly in the outskirts of the large HFF clusters. Five additional orbits are reserved for transient followup. BUFFALO data including mosaics, value-added catalogs and cluster mass distribution models will be released via MAST on a regular basis, as the observations and analysis are completed for the six individual clusters.

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arXiv2019

Science from an Ultra-Deep, High-Resolution Millimeter-Wave Survey

Opening up a new window of millimeter-wave observations that span frequency bands in the range of 30 to 500 GHz, survey half the sky, and are both an order of magnitude deeper (about 0.5 uK-arcmin) and of higher-resolution (about 10 arcseconds) than currently funded surveys would yield an enormous gain in understanding of both fundamental physics and astrophysics. In particular, such a survey would allow for major advances in measuring the distribution of dark matter and gas on small-scales, and yield needed insight on 1.) dark matter particle properties, 2.) the evolution of gas and galaxies, 3.) new light particle species, 4.) the epoch of inflation, and 5.) the census of bodies orbiting in the outer Solar System.

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arXiv2018

Deep CFHT Y-band imaging of VVDS-F22 field: I. data products and photometric redshifts

We present our deep $Y$-band imaging data of a two square degree field within the F22 region of the VIMOS VLT Deep Survey. The observations were conducted using the WIRCam instrument mounted at the Canada--France--Hawaii Telescope (CFHT). The total on-sky time was 9 hours, distributed uniformly over 18 tiles. The scientific goals of the project are to select faint quasar candidates at redshift $z>2.2$, and constrain the photometric redshifts for quasars and galaxies. In this paper, we present the observation and the image reduction, as well as the photometric redshifts that we derived by combining our $Y$-band data with the CFHTLenS $u^*g'r'i'z'$ optical data and UKIDSS DXS $JHK$ near-infrared data. With $J$-band image as reference total $\sim$80,000 galaxies are detected in the final mosaic down to $Y$-band $5σ$ point source limiting depth of 22.86 mag. Compared with the $\sim$3500 spectroscopic redshifts, our photometric redshifts for galaxies with $z<1.5$ and $i'\lesssim24.0$ mag have a small systematic offset of $|Δ{z}|\lesssim0.2$, 1$σ$ scatter $0.03<σ_{Δz} < 0.06$, and less than 4.0% of catastrophic failures. We also compare to the CFHTLenS photometric redshifts, and find that ours are more reliable at $z\gtrsim0.6$ because of the inclusion of the near-infrared bands. In particular, including the $Y$-band data can improve the accuracy at $z\sim 1.0-2.0$ because the location of the 4000Å-break is better constrained. The $Y$-band images, the multi-band photometry catalog and the photometric redshifts are released at \url{http://astro.pku.edu.cn/astro/data/DYI.html}.

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arXiv2018

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 $μ_{\star}$, 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 $μ_{\star}$ bins to measure a mass-observable power law relation. For redMaPPer clusters we obtain $M_0 = (1.77 \pm 0.36) \times 10^{14}h^{-1} M_{\odot}$, $α= 1.74 \pm 0.62$. For VT clusters, we find $M_0 = (4.31 \pm 0.89) \times 10^{14}h^{-1} M_{\odot}$, $α= 0.59 \pm 0.54$ and $M_0 = (3.67 \pm 0.56) \times 10^{14}h^{-1} M_{\odot}$, $α= 0.68 \pm 0.49$ 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 $μ_{\star}$ be used as the mass proxy for VT clusters. Catalogs including $μ_{\star}$ measurements will enable its use in studies of galaxy evolution in clusters and cluster cosmology.

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arXiv2018

Morpho-z: improving photometric redshifts with galaxy morphology

We conduct a comprehensive study of the effects of incorporating galaxy morphology information in photometric redshift estimation. Using machine learning methods, we assess the changes in the scatter and catastrophic outlier fraction of photometric redshifts when galaxy size, ellipticity, Sérsic index and surface brightness are included in training on galaxy samples from the SDSS and the CFHT Stripe-82 Survey (CS82). We show that by adding galaxy morphological parameters to full $ugriz$ photometry, only mild improvements are obtained, while the gains are substantial in cases where fewer passbands are available. For instance, the combination of $grz$ photometry and morphological parameters almost fully recovers the metrics of $5$-band photometric redshifts. We demonstrate that with morphology it is possible to determine useful redshift distribution $N(z)$ of galaxy samples without any colour information. We also find that the inclusion of quasar redshifts and associated object sizes in training improves the quality of photometric redshift catalogues, compensating for the lack of a good star-galaxy separator. We further show that morphological information can mitigate biases and scatter due to bad photometry. As an application, we derive both point estimates and posterior distributions of redshifts for the official CS82 catalogue, training on morphology and SDSS Stripe-82 $ugriz$ bands when available. Our redshifts yield a 68th percentile error of $0.058(1+z)$, and a catastrophic outlier fraction of $5.2$ per cent. We further include a deep extension trained on morphology and single $i$-band CS82 photometry.

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arXiv2018

Do satellite galaxies trace matter in galaxy clusters?

The spatial distribution of satellite galaxies encodes rich information of the structure and assembly history of galaxy clusters. In this paper, we select a redMaPPer cluster sample in SDSS Stripe 82 region with $0.1 \le z \le 0.33$, $20<λ<100$ and $P_{\rm cen}>0.7$. Using the high-quality weak lensing data from CS82 Survey, we constrain the mass profile of this sample. Then we compare directly the mass density profile with the satellite number density profile. We find that the total mass and number density profiles have the same shape, both well fitted by an NFW profile. The scale radii agree with each other within 1$σ$ error ($r_{\rm s,gal}=0.34_{-0.03}^{+0.04}$Mpc vs $r_{\rm s}=0.37_{-0.10}^{+0.15}$Mpc ).

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arXiv2018

Deep CFHT Y-band Imaging of VVDS-F22 Field: II. Quasar Selection and Quasar Luminosity Function

We report the result of a faint quasar survey in a one square degree field. The aim is to test the Y-K/g-z and J-K/i-Y color selection criteria for quasars at faint magnitude, to obtain a complete sample of quasars based on deep optical and near-infrared color-color selection, and to measure the faint end of quasar luminosity function (QLF) over a wide redshift range. We carried out a quasar survey based on the Y-K/g-z and J-K/i-Y quasar selection criteria, using the deep Y-band data obtained from our CFHT/WIRCam Y-band images in a two-degree field within the F22 field of the VIMOS VLT deep survey, optical co-added data from Sloan Digital Sky Survey Stripe 82 and deep near-infrared data from the UKIDSS Deep Extragalactic Survey in the same field. We discovered 25 new quasars at 0.5 < z < 4.5 and i < 22.5 mag within one square degree field. The survey significantly increases the number of faint quasars in this field, especially at z ~ 2-3. It confirms that our color selections are highly complete in a wide redshift range (z < 4.5), especially over the quasar number density peak at z ~ 2-3, even for faint quasars. Combining all previous known quasars and new discoveries, we construct a sample with 109 quasars, and measure the binned QLF and parametric QLF. Although the sample is small, our results agree with a pure luminosity evolution at lower redshift and luminosity evolution and density evolution model at redshift z > 2.5.

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arXiv2017

The Mass-Concentration Relation and the Stellar-to-Halo Mass Ratio in the CFHT Stripe 82 Survey

We present a new measurement of the mass-concentration relation and the stellar-to-halo mass ratio over the halo mass range $5\times 10^{12}$ to $2\times 10^{14}M_{\odot}$. To achieve this, we use weak lensing measurements from the CFHT Stripe 82 Survey (CS82), combined with the central galaxies from the redMaPPer cluster catalogue and the LOWZ/CMASS galaxy sample of the Sloan Digital Sky Survey-III Baryon Oscillation Spectroscopic Survey Tenth Data Release. The stacked lensing signals around these samples are modelled as a sum of contributions from the central galaxy, its dark matter halo, and the neighboring halos, as well as a term for possible centering errors. We measure the mass-concentration relation: $c_{200c}(M)=A(\frac{M_{200c}}{M_0})^{B}$ with $A=5.24\pm1.24, B=-0.13\pm0.10$ for $0.2<z<0.4$ and $A=6.61\pm0.75, B=-0.15\pm0.05$ for $0.4<z<0.6$. These amplitudes and slopes are completely consistent with predictions from recent simulations. We also measure the stellar-to-halo mass ratio for our samples, and find results consistent with previous measurements from lensing and other techniques.

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arXiv2017

Stellar-to-halo mass relation of cluster galaxies

In the hierarchical formation model, galaxy clusters grow by accretion of smaller groups or isolated galaxies. During the infall into the centre of a cluster, the properties of accreted galaxies change. In particular, both observations and numerical simulations suggest that its dark matter halo is stripped by the tidal forces of the host. We use galaxy-galaxy weak lensing to measure the average mass of dark matter haloes of satellite galaxies as a function of projected distance to the centre of the host, for different stellar mass bins. Assuming that the stellar component of the galaxy is less disrupted by tidal stripping, stellar mass can be used as a proxy of the infall mass. We study the stellar to halo mass relation of satellites as a function of the cluster-centric distance to measure tidal stripping. We use the shear catalogues of the DES science verification archive, the CFHTLenS and the CFHT Stripe 82 (CS82) surveys, and we select satellites from the redMaPPer catalogue of clusters. For galaxies located in the outskirts of clusters, we find a stellar to halo mass relation in good agreement with the theoretical expectations from \citet{moster2013} for central galaxies. In the centre of the cluster, we find that this relation is shifted to smaller halo mass for a given stellar mass. We interpret this finding as further evidence for tidal stripping of dark matter haloes in high density environments.

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arXiv2016

Measuring subhalo mass in redMaPPer clusters with CFHT Stripe 82 Survey

We use the shear catalog from the CFHT Stripe-82 Survey to measure the subhalo masses of satellite galaxies in redMaPPer clusters. Assuming a Chabrier Initial Mass Function (IMF) and a truncated NFW model for the subhalo mass distribution, we find that the sub-halo mass to galaxy stellar mass ratio increases as a function of projected halo-centric radius $r_p$, from $M_{\rm sub}/M_{\rm star}=4.43^{+ 6.63}_{- 2.23}$ at $r_p \in [0.1,0.3]$ $h^{-1}Mpc$ to $M_{\rm sub}/M_{\rm star}=75.40^{+ 19.73}_{- 19.09}$ at $r_p \in [0.6,0.9]$ $h^{-1}Mpc$. We also investigate the dependence of subhalo masses on stellar mass by splitting satellite galaxies into two stellar mass bins: $10<\log(M_{\rm star}/M_{\rm sun})<10.5$ and $11<\log(M_{\rm star}/M_{\rm sun})<12$. The best-fit subhalo mass of the more massive satellite galaxy bin is larger than that of the less massive satellites: $\log(M_{\rm sub}/M_{\rm sun})=11.14 ^{+ 0.66 }_{- 0.73}$ ($M_{\rm sub}/M_{\rm star}=19.5^{+19.8}_{-17.9}$) versus $\log(M_{\rm sub}/M_{\rm sun})=12.38 ^{+ 0.16 }_{- 0.16}$ ($M_{\rm sub}/M_{\rm star}=21.1^{+7.4}_{-7.7}$).

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arXiv2015

Mass-concentration relation of clusters of galaxies from CFHTLenS

Based on weak lensing data from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), in this paper we study the mass-concentration ($M$-$c$) relation for $\sim 200$ redMaPPer clusters in the fields. We extract the $M$-$c$ relation by measuring the density profiles of individual clusters instead of using stacked weak lensing signals. By performing Monte Carlo simulations, we demonstrate that although the signal-to-noise ratio for each individual cluster is low, the unbiased $M$-$c$ relation can still be reliably derived from a large sample of clusters by carefully taking into account the impacts of shape noise, cluster center offset, dilution effect from member or foreground galaxies, and the projection effect. Our results show that within error bars the derived $M$-$c$ relation for redMaPPer clusters is in agreement with simulation predictions. There is a weak deviation in that the halo concentrations calibrated by Monte Carlo simulations are somewhat higher than that predicted from ${\it Planck}$ cosmology.

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arXiv2015

Cosmological Constraints From Weak Lensing Peak Statistics With CFHT Stripe 82 Survey

We derived constraints on cosmological parameters using weak lensing peak statistics measured on the $\sim130~{\rm deg}^2$ of the Canada-France-Hawaii Telescope Stripe 82 Survey (CS82). This analysis demonstrates the feasibility of using peak statistics in cosmological studies. For our measurements, we considered peaks with signal-to-noise ratio in the range of $ν=[3,6]$. For a flat $Λ$CDM model with only $(Ω_{\rm m}, σ_8)$ as free parameters, we constrained the parameters of the following relation $Σ_8=σ_8(Ω_{\rm m}/0.27)^α$ to be: $Σ_8=0.82 \pm 0.03 $ and $α=0.43\pm 0.02$. The $α$ value found is considerably smaller than the one measured in two-point and three-point cosmic shear correlation analyses, showing a significant complement of peak statistics to standard weak lensing cosmological studies. The derived constraints on $(Ω_{\rm m}, σ_8)$ are fully consistent with the ones from either WMAP9 or Planck. From the weak lensing peak abundances alone, we obtained marginalised mean values of $Ω_{\rm m}=0.38^{+0.27}_{-0.24}$ and $σ_8=0.81\pm 0.26$. Finally, we also explored the potential of using weak lensing peak statistics to constrain the mass-concentration relation of dark matter halos simultaneously with cosmological parameters.

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arXiv2015

Overview of Complementarity and Synergy with Other Wavelengths in Cosmology in the SKA era

We give an overview of complementarity and synergy in cosmology between the Square Kilometre Array and future survey projects in other wavelengths. In the SKA era, precision cosmology will be limited by systematic errors and cosmic variance, rather than statistical errors. However, combining and/or cross-correlating multi-wavelength data, from the SKA to the cosmic microwave background, optical/infrared and X-ray, substantially reduce these limiting factors. In this chapter, we summarize future survey projects and show highlights of complementarity and synergy, which can be very powerful to probe major cosmological problems such as dark energy, modified gravity and primordial non-Gaussianity.

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arXiv2014

First Measurement of the Cross-Correlation of CMB Lensing and Galaxy Lensing

We measure the cross-correlation of cosmic microwave background lensing convergence maps derived from Atacama Cosmology Telescope data with galaxy lensing convergence maps as measured by the Canada-France-Hawaii Telescope Stripe 82 Survey. The CMB-galaxy lensing cross power spectrum is measured for the first time with a significance of 4.2σ, which corresponds to a 12% constraint on the amplitude of density fluctuations at redshifts ~ 0.9. With upcoming improved lensing data, this novel type of measurement will become a powerful cosmological probe, providing a precise measurement of the mass distribution at intermediate redshifts and serving as a calibrator for systematic biases in weak lensing measurements.

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arXiv2013

First Galaxy-Galaxy Lensing Measurement of Satellite Halo Mass in the CFHT Stripe-82 Survey

We select satellite galaxies from the galaxy group catalog constructed with the SDSS spectroscopic galaxies and measure the tangential shear around these galaxies with source catalog extracted from CFHT/MegaCam Stripe-82 Survey to constrain the mass of subhalos associated with them. The lensing signal is measured around satellites in groups with masses in the range [10^{13}, 5x10^{14}]h^{-1}M_{sun}, and is found to agree well with theoretical expectation. Fitting the data with a truncated NFW profile, we obtain an average subhalo mass of log M_{sub}= 11.68 \pm 0.67 for satellites whose projected distances to central galaxies are in the range [0.1, 0.3] h^{-1}Mpc, and log M_{sub}= 11.68 \pm 0.76 for satellites with projected halo-centric distance in [0.3, 0.5] h^{-1}Mpc. The best-fit subhalo masses are comparable to the truncated subhalo masses assigned to satellite galaxies using abundance matching and about 5 to 10 times higher than the average stellar mass of the lensing satellite galaxies.

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arXiv2010

Comparison of Halo Detection from Noisy Weak Lensing Convergence Maps with Gaussian Smoothing and MRLens Treatment

Taking into account the noise from intrinsic ellipticities of source galaxies, we study the efficiency and completeness of halo detections from weak lensing convergence maps. Particularly, with numerical simulations, we compare the Gaussian filter with the so called MRLens treatment based on the modification of the Maximum Entropy Method. For a pure noise field without lensing signals, a Gaussian smoothing results a residual noise field that is approximately Gaussian in statistics if a large enough number of galaxies are included in the smoothing window. On the other hand, the noise field after the MRLens treatment is significantly non-Gaussian, resulting complications in characterizing the noise effects. Considering weak-lensing cluster detections, although the MRLens treatment effectively deletes false peaks arising from noise, it removes the real peaks heavily due to its inability to distinguish real signals with relatively low amplitudes from noise in its restoration process. The higher the noise level is, the larger the removal effects are for the real peaks. For a survey with a source density n_g~30 arcmin^(2), the number of peaks found in an area of 3x3 sq.deg after MRLens filtering is only ~50 for the detection threshold kappa=0.02, while the number of halos with M>5x10^{13} M_{\odot} and with redshift z<=2 in the same area is expected to be ~530. For the Gaussian smoothing treatment, the number of detections is ~260, much larger than that of the MRLens. The Gaussianity of the noise statistics in the Gaussian smoothing case adds further advantages for this method to circumvent the problem of the relatively low efficiency in weak-lensing cluster detections. Therefore, in studies aiming to construct large cluster samples from weak-lensing surveys, the Gaussian smoothing method performs significantly better than the MRLens.

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