分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We carry out a thermal energy census of hot baryons at $z < 1$, by cross-correlating the \emph{Planck} MILCA y-map with 0.8 million clusters/groups selected from the Yang et.al (2021) catalog. The thermal Sunyaev-Zel'dovich (tSZ) effect around these clusters/groups are reliably obtained, which enables us to make our model constraints based on one-halo (1h) and two-halo (2h) contributions, respectively. (1) The total measurement S/N of the one-halo term is 63. We constrain the $Y$-$M$ relation over the halo mass range of $10^{13}$-$10^{15} M_\odot/h$, and find $Y\propto M^{\alpha}$ with $\alpha= 1.8$ at $z=0.14$ ($\alpha=2.1$ at $z=0.75$). The total thermal energy of gas bound to clusters/groups increases from $0.1\ \rm meV/cm^3$ at $z=0.14$ to $0.22\ \rm meV/cm^3$ at $z=0.75$. (2) The two-halo term is used to constrain the bias-weighted electron pressure $\langle b_yP_e \rangle$. We find that $\langle b_yP_e \rangle$ (in unit of $\rm meV/cm^3$) increases from $0.24\pm 0.02$ at $z=0.14$ to $0.45\pm 0.02$ at $z=0.75$. These results lead to several implications. (i) The hot gas fraction $f_{\rm gas}$ in clusters/groups monotonically increase with halo mass, where $f_{\rm gas}$ of a $10^{14} M_\odot/h$ halo is $\sim 50\%$ ($25\%$) of the cosmic mean at $z=0.14\ (0.75)$. (ii) By comparing the 1h- and 2h-terms, we obtain tentative constraint on the thermal energy of unbound gas. (iii) The above results lead to significant suppression of matter and weak lensing power spectrum at small scales. These implications are important for astrophysics and cosmology, and we will further investigate them with improved data and gas modeling.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We carry out a thermal energy census of hot baryons at $z < 1$, by cross-correlating the \emph{Planck} MILCA y-map with 0.8 million clusters/groups selected from the Yang et.al (2021) catalog. The thermal Sunyaev-Zel'dovich (tSZ) effect around these clusters/groups are reliably obtained, which enables us to make our model constraints based on one-halo (1h) and two-halo (2h) contributions, respectively. (1) The total measurement S/N of the one-halo term is 63. We constrain the $Y$-$M$ relation over the halo mass range of $10^{13}$-$10^{15} M_\odot/h$, and find $Y\propto M^{\alpha}$ with $\alpha= 1.8$ at $z=0.14$ ($\alpha=2.1$ at $z=0.75$). The total thermal energy of gas bound to clusters/groups increases from $0.1\ \rm meV/cm^3$ at $z=0.14$ to $0.22\ \rm meV/cm^3$ at $z=0.75$. (2) The two-halo term is used to constrain the bias-weighted electron pressure $\langle b_yP_e \rangle$. We find that $\langle b_yP_e \rangle$ (in unit of $\rm meV/cm^3$) increases from $0.24\pm 0.02$ at $z=0.14$ to $0.45\pm 0.02$ at $z=0.75$. These results lead to several implications. (i) The hot gas fraction $f_{\rm gas}$ in clusters/groups monotonically increase with halo mass, where $f_{\rm gas}$ of a $10^{14} M_\odot/h$ halo is $\sim 50\%$ ($25\%$) of the cosmic mean at $z=0.14\ (0.75)$. (ii) By comparing the 1h- and 2h-terms, we obtain tentative constraint on the thermal energy of unbound gas. (iii) The above results lead to significant suppression of matter and weak lensing power spectrum at small scales. These implications are important for astrophysics and cosmology, and we will further investigate them with improved data and gas modeling.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Based on galaxies in the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) and dark matter haloes in the dark matter only, cosmological and constrained ELUCID simulation, we investigate the relation between the observed radii of central galaxies with stellar mass $\gtrsim 10^{8} h^{-2}{\rm M}_\odot$ and the virial radii of their host dark matter haloes with virial mass $\gtrsim 10^{10.5} h^{-1}{\rm M}_\odot$, and the dependence of galaxy-halo size relation on the halo spin and concentration. Galaxies in observation are matched to dark matter (sub-)haloes in the ELUCID simulation using a novel neighborhood subhalo abundance matching method. For galaxy 2D half-light radii $R_{50}$, we find that early- and late-type galaxies have the same power-law index 0.55 with $R_{50} \propto R_{\rm vir}^{0.55}$, although early-type galaxies have smaller 2D half-light radii than late-type galaxies at fixed halo virial radii. When converting the 2D half-light radii $R_{50}$ to 3D half-mass radii $r_{1/2}$, both early- and late-type galaxies display similar galaxy-halo size relations with $\log r_{1/2} = 0.55 \log (R_{\rm vir}/210 h^{-1}{\rm kpc}) + 0.39$. We find that the galaxy-halo size ratio $r_{1/2}/ R_{\rm vir}$ decreases with increasing halo mass. At fixed halo mass, there is no significant dependence of galaxy-halo size ratio on the halo spin or concentration.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： By linking galaxies in Sloan Digital Sky Survey (SDSS) to subhaloes in the ELUCID simulation, we investigate the relation between subhalo formation time and the galaxy properties, and the dependence of galaxy properties on the cosmic web environment. We find that central and satellite subhaloes have different formation time, where satellite subhaloes are older than central subhaloes at fixed mass. At fixed mass, the galaxy stellar-to-subhalo mass ratio is a good proxy of the subhalo formation time, and increases with the subhalo formation redshifts, especially for massive galaxies. The subhalo formation time is dependent on the cosmic web environment. For central subhaloes, there is a characteristic subhalo mass of $\sim 10^{12} \msun$, below which subhaloes in knots are older than subhaloes of the same mass in filaments, sheets, or voids, while above which it reverses. The cosmic web environmental dependence of stellar-to-subhalo mass ratio is similar to that of the subhalo formation time. For centrals, there is a characteristic subhalo mass of $\sim 10^{12} \msun$, below which the stellar-to-subhalo mass ratio is higher in knots than in filaments, sheets and voids, above which it reverses. Galaxies in knots have redder colors below $10^{12} \msun$, while above $10^{12} \msun$, the environmental dependence vanishes. Satellite fraction is strongly dependent on the cosmic web environment, and decreases from knots to filaments to sheets to voids, especially for low-mass galaxies.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We report a $5\sigma$ detection of the pairwise kinematic Sunyaev-Zel'dovich (kSZ) effect, combining galaxy clusters in DESI imaging surveys and the Planck temperature maps. The detection is facilitated by both improvements in the data and in the analysis method. For the data, we adopt the recently released galaxy group catalog (Y20: \cite{yang2020extended}) with $\sim 10^6$ robustly-identified groups, and construct various galaxy cluster samples for the kSZ measurement. The Y20 catalogue also provides estimation of halo mass, which further improves the kSZ measurement by $\sim 10\%$. For the analysis method, we derive an optimal estimator of pairwise kSZ through the maximum likelihood analysis. It also handles potential systematic errors self-consistently. The baseline cluster sample, containing the $1.2\times 10^5$ richest galaxy clusters of typical mass ~$ 10^{14} M_{\odot}/h$ at typical redshift $0.2$-$0.5$, rules out the null hypothesis at $5\sigma$. When fitting with a pairwise kSZ template from simulations, the signal is detected at $4.7\sigma$ and the average optical depth is constrained as $\bar{\tau}_e=(1.66\pm 0.35)\times 10^{-4}$. We perform various internal checks, with different cluster selection criteria, different sky coverage and redshift range, different CMB maps, different filter sizes, different treatments of potential systematics and the covariance matrix. The kSZ effect is consistently detected with $2.5\leq $S/N$\leq 5.6$ and acceptable $\chi^2_{\rm min}$, across a variety of cluster samples. The S/N is limited by both the Planck resolution and the photo-z accuracy, and therefore can be significant improved with DESI spectroscopic redshift information and with other CMB experiments.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Using hydrodynamical simulations, we study how well the underlying gravitational potential of a galaxy cluster can be modelled dynamically with different types of tracers. In order to segregate different systematics and the effects of varying estimator performances, we first focus on applying a generic minimal assumption method (oPDF) to model the simulated haloes using the full 6-D phasespace information. We show that the halo mass and concentration can be recovered in an ensemble unbiased way, with a stochastic bias that varies from halo to halo, mostly reflecting deviations from steady state in the tracer distribution. The typical systematic uncertainty is $\sim 0.17$ dex in the virial mass and $\sim 0.17$ dex in the concentration as well when dark matter particles are used as tracers. The dynamical state of satellite galaxies are close to that of dark matter particles, while intracluster stars are less in a steady state, resulting in a $\sim$ 0.26 dex systematic uncertainty in mass. Compared with galactic haloes hosting Milky-Way-like galaxies, cluster haloes show a larger stochastic bias in the recovered mass profiles. We also test the accuracy of using intracluster gas as a dynamical tracer modelled through a generalised hydrostatic equilibrium equation, and find a comparable systematic uncertainty in the estimated mass to that using dark matter. Lastly, we demonstrate that our conclusions are largely applicable to other steady-state dynamical models including the spherical Jeans equation, by quantitatively segregating their statistical efficiencies and robustness to systematics. We also estimate the limiting number of tracers that leads to the systematics-dominated regime in each case.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We measure the cross-correlation between galaxy groups constructed from DESI
Legacy Imaging Survey DR8 and \emph{Planck} CMB lensing, over overlapping sky
area of 16876 $\rm deg^2$. The detections are significant and consistent with
the expected signal of the large-scale structure of the universe, over group
samples of various redshift, mass, richness $N_{\rm g}$ and over various scale
cuts. The overall S/N is 40 for a conservative sample with $N_{\rm g}\geq 5$,
and increases to $50$ for the sample with $N_{\rm g}\geq 2$. Adopting the
\emph{Planck} 2018 cosmology, we constrain the density bias of groups with
$N_{\rm g}\geq 5$ as $b_{\rm g}=1.31\pm 0.10$, $2.22\pm 0.10$, $3.52\pm 0.20$
at $0.1
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We employ a set of high resolution N-body simulations to study the merger rate of dark matter halos. We define a specific merger rate by normalizing the average number of mergers per halo with the logarithmic mass growth change of the hosts at the time of accretion. Based on the simulation results, we find that this specific merger rate, $\mathrm{d}N_{\mathrm{merge}}(\xi|M,z)/\mathrm{d}\xi/\mathrm{d}\log M(z)$, has a universal form, which is only a function of the mass ratio of merging halo pairs, $\xi$, and does not depend on the host halo mass, $M$, or redshift, $z$, over a wide range of masses ($10^{12}\lesssim M \lesssim10^{14}\,M_\odot/h$) and merger ratios ($\xi\ge 1e-2$). We further test with simulations of different $\Omega_m$ and $\sigma_8$, and get the same specific merger rate. The universality of the specific merger rate shows that halos in the universe are built up self-similarly, with a universal composition in the mass contributions and an absolute merger rate that grows in proportion to the halo mass growth. As a result, the absolute merger rate relates with redshift and cosmology only through the halo mass variable, whose evolution can be readily obtained from the universal mass accretion history (MAH) model of \cite{2009ApJ...707..354Z}. Lastly, we show that this universal specific merger rate immediately predicts an universal un-evolved subhalo mass function that is independent on the redshift, MAH or the final halo mass, and vice versa.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Low Density Points (LDPs, \citet{2019ApJ...874....7D}), obtained by removing
high-density regions of observed galaxies, can trace the Large-Scale Structures
(LSSs) of the universe. In particular, it offers an intriguing opportunity to
detect weak gravitational lensing from low-density regions. In this work, we
investigate tomographic cross-correlation between Planck CMB lensing maps and
LDP-traced LSSs, where LDPs are constructed from the DR8 data release of the
DESI legacy imaging survey, with about $10^6$-$10^7$ galaxies. We find that,
due to the large sky coverage (20,000 deg$^2$) and large redshift depth ($z\leq
1.2$), a significant detection ($10\sigma$--$30\sigma$) of the CMB lensing-LDP
cross-correlation in all six redshift bins can be achieved, with a total
significance of $\sim 53\sigma$ over $ \ell\le1024$. Moreover, the measurements
are in good agreement with a theoretical template constructed from our
numerical simulation in the WMAP 9-year $\Lambda$CDM cosmology. A scaling
factor for the lensing amplitude $A_{\rm lens}$ is constrained to $A_{\rm
lens}=1\pm0.12$ for $z<0.2$, $A_{\rm lens}=1.07\pm0.07$ for $0.2
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present an algorithm to extend subhalo merger trees in a low-resolution dark-matter-only simulation by conditionally matching them to those in a high-resolution simulation. The algorithm is general and can be applied to simulation data with different resolutions using different target variables. We instantiate the algorithm by a case in which trees from ELUCID, a constrained simulation of $(500h^{-1}{\rm Mpc})^3$ volume of the local universe, are extended by matching trees from TNGDark, a simulation with much higher resolution. Our tests show that the extended trees are statistically equivalent to the high-resolution trees in the joint distribution of subhalo quantities and in important summary statistics relevant to modeling galaxy formation and evolution in halos. The extended trees preserve certain information of individual systems in the target simulation, including properties of resolved satellite subhalos, and shapes and orientations of their host halos. With the extension, subhalo merger trees in a cosmological scale simulation are extrapolated to a mass resolution comparable to that in a higher-resolution simulation carried out in a smaller volume, which can be used as the input for (sub)halo-based models of galaxy formation. The source code of the algorithm, and halo merger trees extended to a mass resolution of $\sim 2 \times 10^8 h^{-1}M_\odot$ in the entire ELUCID simulation, are available.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present an algorithm to extend subhalo merger trees in a low-resolution dark-matter-only simulation by conditionally matching them to those in a high-resolution simulation. The algorithm is general and can be applied to simulation data with different resolutions using different target variables. We instantiate the algorithm by a case in which trees from ELUCID, a constrained simulation of $(500h^{-1}{\rm Mpc})^3$ volume of the local universe, are extended by matching trees from TNGDark, a simulation with much higher resolution. Our tests show that the extended trees are statistically equivalent to the high-resolution trees in the joint distribution of subhalo quantities and in important summary statistics relevant to modeling galaxy formation and evolution in halos. The extended trees preserve certain information of individual systems in the target simulation, including properties of resolved satellite subhalos, and shapes and orientations of their host halos. With the extension, subhalo merger trees in a cosmological scale simulation are extrapolated to a mass resolution comparable to that in a higher-resolution simulation carried out in a smaller volume, which can be used as the input for (sub)halo-based models of galaxy formation. The source code of the algorithm, and halo merger trees extended to a mass resolution of $\sim 2 \times 10^8 h^{-1}M_\odot$ in the entire ELUCID simulation, are available.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Cluster cosmology depends critically on how the optical clusters are selected from imaging surveys. We compare the conditional luminosity function (CLF) and weak lensing halo masses between two different cluster samples at fixed richness, detected within the same volume ($0.1{<}z{<}0.34$) using the red-sequence and halo-based methods. After calibrating our CLF deprojection method against mock galaxy samples, we measure the 3D CLFs by cross-correlating clusters with SDSS photometric galaxies. As expected, the CLFs of the red-sequence and halo-based finders exhibit redder and bluer populations, respectively. We also find significant shape discrepancies between the two CLFs at the faint end, where the red-sequence clusters show a strong deficit of faint galaxies but a bump at $M_r{\sim}-20.5$, while the halo-based clusters host an increasing number of blue satellites. By comparing the subsamples of clusters that have a match between the two catalogues to those without matches, we discover that the CLF shape depends sensitively on the cluster centroiding. However, the average weak lensing halo mass between the matched and non-matched clusters are roughly consistent with each other in either cluster sample. Since the colour preferences of the two cluster finders are almost orthogonal, such a consistency indicates that the scatter in the mass-richness relation of either cluster sample is close to random. Therefore, while the choice of how optical clusters are identified impacts the satellite content, our result suggests that it should not introduce strong systematics biases in cluster cosmology.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： In a recent study, we developed a method to model the impact of photometric redshift uncertainty on the two-point correlation function (2PCF). In this method, we can obtain both the intrinsic clustering strength and the photometric redshift errors simultaneously by fitting the projected 2PCF with two integration depths along the line-of-sight. Here we apply this method to the DESI Legacy Imaging Surveys Data Release 8 (LS DR8), the largest galaxy sample currently available. We separate galaxies into 20 samples in 8 redshift bins from $z=0.1$ to $z=1.0$, and a few $\rm z$-band absolute magnitude bins, with $M_{\rm z} \le -20$. These galaxies are further separated into red and blue sub-samples according to their $M^{0.5}_{\rm r}-M^{0.5}_{\rm z}$ colors. We measure the projected 2PCFs for all these galaxy (sub-)samples, and fit them using our photometric redshift 2PCF model. We find that the photometric redshift errors are smaller in red sub-samples than the overall population. On the other hand, there might be some systematic photometric redshift errors in the blue sub-samples, so that some of the sub-samples show significantly enhanced 2PCF at large scales. Therefore, focusing only on the red and all (sub-)samples, we find that the biases of galaxies in these (sub-)samples show clear color, redshift and luminosity dependencies, in that red brighter galaxies at higher redshift are more biased than their bluer and low redshift counterparts. Apart from the best fit set of parameters, $\sigma_{z}$ and $b$, from this state-of-the-art photometric redshift survey, we obtain high precision intrinsic clustering measurements for these 40 red and all galaxy (sub-)samples. These measurements on large and small scales hold important information regarding the cosmology and galaxy formation, which will be used in our subsequent probes in this series.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We investigate the importances of various dynamical features in predicting the dynamical state (DS) of galaxy clusters, based on the Random Forest (RF) machine learning approach. We use a large sample of galaxy clusters from the Three Hundred Project of hydrodynamical zoomed-in simulations, and construct dynamical features from the raw data as well as from the corresponding mock maps in the optical, X-ray, and Sunyaev-Zel'dovich (SZ) channels. Instead of relying on the impurity based feature importance of the RF algorithm, we directly use the out-of-bag (OOB) scores to evaluate the importances of individual features and different feature combinations. Among all the features studied, we find the virial ratio, $\eta$, to be the most important single feature. The features calculated directly from the simulations and in 3-dimensions carry more information on the DS than those constructed from the mock maps. Compared with the features based on X-ray or SZ maps, features related to the centroid positions are more important. Despite the large number of investigated features, a combination of up to three features of different types can already saturate the score of the prediction. Lastly, we show that the most sensitive feature $\eta$ is strongly correlated with the well-known half-mass bias in dynamical modelling. Without a selection in DS, cluster halos have an asymmetric distribution in $\eta$, corresponding to an overall positive half-mass bias. Our work provides a quantitative reference for selecting the best features to discriminate the DS of galaxy clusters in both simulations and observations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： In the local Universe, the efficiency for converting baryonic gas into stars is very low. In dark matter halos where galaxies form and evolve, the average efficiency varies with galaxy stellar mass and has a maximum of about twenty percent for Milky-Way-like galaxies. The low efficiency at higher mass is believed to be produced by some quenching processes, such as the feedback from active galactic nuclei. We perform an analysis of weak lensing and satellite kinematics for SDSS central galaxies. Our results reveal that the efficiency is much higher, more than sixty percent, for a large population of massive star-forming galaxies around $10^{11}M_{\odot}$. This suggests that these galaxies acquired most of the gas in their halos and converted it into stars without being affected significantly by quenching processes. This population of galaxies is not reproduced in current galaxy formation models, indicating that our understanding of galaxy formation is incomplete. The implications of our results on circumgalactic media, star formation quenching and disc galaxy rotation curves are discussed. We also examine systematic uncertainties in halo-mass and stellar-mass measurements that might influence our results.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Wentao Luo
Jiajun Zhang
Vitali Halenka
Xiaohu Yang
Surhud More
Chris Miller
Tomomi Sunayama
Lei Liu
Feng Shi
摘要： We test the Emergent Gravity(EG) theory using the galaxy-galaxy lensing technique based on SDSS DR7 data. In the EG scenario, we do not expect color dependence of the galaxy sample in the 'apparent dark matter' predicted by EG, which is exerted only by the baryonic mass. If the baryonic mass is similar, then the predicted lensing profiles from the baryonic mass should be similar according to the EG, regardless of the color of the galaxy sample. We use the stellar mass of the galaxy as a proxy of its baryonic mass. We divide our galaxy sample into 5 stellar mass bins, and further classify them as red and blue subsamples in each stellar mass bin. If we set halo mass and concentration as free parameters, $\Lambda$CDM is favored by our data in terms of the reduced $\chi^2$ while EG fails to explain the color dependence of ESDs from the galaxy-galaxy lensing measurement.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Recent observations reveal that, at a given stellar mass, blue galaxies tend to live in haloes with lower mass while red galaxies live in more massive host haloes. The physical driver behind this is still unclear because theoretical models predict that, at the same halo mass, galaxies with high stellar masses tend to live in early-formed haloes which naively leads to an opposite trend. Here, we show that the {\sc Simba} simulation quantitatively reproduces the colour bimodality in SHMR and reveals an inverse relationship between halo formation time and galaxy transition time. It suggests that the origin of this bimodality is rooted in the intrinsic variations of the cold gas content due to halo assembly bias. {\sc Simba}'s SHMR bimodality quantitatively relies on two aspects of its input physics: (1) Jet-mode AGN feedback, which quenches galaxies and sets the qualitative trend; and (2) X-ray AGN feedback, which fully quenches galaxies and yields better agreement with observations. The interplay between the growth of cold gas and the AGN quenching in {\sc Simba} results in the observed SHMR bimodality.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We develop a model to establish the interconnection between galaxies and their dark matter halos. We use Principal Component Analysis (PCA) to reduce the dimensionality of both the mass assembly histories of halos/subhalos and the star formation histories of galaxies, and Gradient Boosted Decision Trees (GBDT) to transform halo/subhalo properties into galaxy properties. We use two sets of hydrodynamic simulations to motivate our model architecture and to train the transformation. We then apply the two sets of trained models to dark matter only (DMO) simulations to show that the transformation is reliable and statistically accurate. The model trained by a high-resolution hydrodynamic simulation, or by a set of such simulations implementing the same physics of galaxy formation, can thus be applied to large DMO simulations to make "mock" copies of the hydrodynamic simulation. The model is both flexible and interpretable, which paves the way for future applications in which we will constrain the model using observations at different redshifts simultaneously and explore how galaxies form and evolve in dark matter halos empirically.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Calibrating the redshift distributions of photometric galaxy samples is essential in weak lensing studies. The self-calibration method combines angular auto- and cross-correlations between galaxies in multiple photometric redshift (photo-$z$) bins to reconstruct the scattering rates matrix between redshift bins. In this paper, we test a recently proposed self-calibration algorithm using the DECaLS Data Release 9 and investigate to what extent the scattering rates are determined. We first mitigate the spurious angular correlations due to imaging systematics by a machine learning based method. We then improve the algorithm for $\chi^2$ minimization and error estimation. Finally, we solve for the scattering matrices, carry out a series of consistency tests and find reasonable agreements: (1) finer photo-$z$ bins return a high-resolution scattering matrix, and it is broadly consistent with the low-resolution matrix from wider bins; (2) the scattering matrix from the Northern Galactic Cap is almost identical to that from Southern Galactic Cap; (3) the scattering matrices are in reasonable agreement with those constructed from the power spectrum and the weighted spectroscopic subsample. We also evaluate the impact of cosmic magnification. Although it changes little the diagonal elements of the scattering matrix, it affects the off-diagonals significantly. The scattering matrix also shows some dependence on scale cut of input correlations, which may be related to a known numerical degeneracy between certain scattering pairs. This work demonstrates the feasibility of the self-calibration method in real data and provides a practical alternative to calibrate the redshift distributions of photometric samples.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Calibrating the redshift distributions of photometric galaxy samples is essential in weak lensing studies. The self-calibration method combines angular auto- and cross-correlations between galaxies in multiple photometric redshift (photo-$z$) bins to reconstruct the scattering rates matrix between redshift bins. In this paper, we test a recently proposed self-calibration algorithm using the DECaLS Data Release 9 and investigate to what extent the scattering rates are determined. We first mitigate the spurious angular correlations due to imaging systematics by a machine learning based method. We then improve the algorithm for $\chi^2$ minimization and error estimation. Finally, we solve for the scattering matrices, carry out a series of consistency tests and find reasonable agreements: (1) finer photo-$z$ bins return a high-resolution scattering matrix, and it is broadly consistent with the low-resolution matrix from wider bins; (2) the scattering matrix from the Northern Galactic Cap is almost identical to that from Southern Galactic Cap; (3) the scattering matrices are in reasonable agreement with those constructed from the power spectrum and the weighted spectroscopic subsample. We also evaluate the impact of cosmic magnification. Although it changes little the diagonal elements of the scattering matrix, it affects the off-diagonals significantly. The scattering matrix also shows some dependence on scale cut of input correlations, which may be related to a known numerical degeneracy between certain scattering pairs. This work demonstrates the feasibility of the self-calibration method in real data and provides a practical alternative to calibrate the redshift distributions of photometric samples.
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