您选择的条件: H. J. Mo
  • Shock-induced stripping of satellite ISM/CGM in IllustrisTNG clusters at $z\sim0$

    分类: 天文学 >> 天文学 提交时间: 2023-02-19

    摘要: Using the IllustrisTNG simulation, we study the interaction of large-scale shocks with the circumgalactic medium (CGM) and interstellar medium (ISM) of star-forming (SF) satellite galaxies in galaxy clusters. These shocks are usually produced by mergers and massive accretion. Our visual inspection shows that approximately half of SF satellites have encountered shocks in their host clusters at $z\leq0.11$. After a satellite crosses a shock front and enters the postshock region, the ram pressure on it is boosted significantly. Both the CGM and ISM can be severely impacted, either by striping or compression. The stripping of the ISM is particularly important for low-mass galaxies with $\log (M_{*}/M_{\odot})<10$ and can occur even in the outskirts of galaxy clusters. In comparison, satellites that do not interact with shocks lose their ISM only in the inner regions of clusters. About half of the ISM is stripped within about 0.6 Gyr after it crosses the shock front. Our results show that shock-induced stripping plays an important role in quenching satellite galaxies in clusters.

  • Finding proto-clusters to trace galaxy evolution: I. The finder and its performance

    分类: 天文学 >> 天文学 提交时间: 2023-02-19

    摘要: We develop a method to identify proto-clusters based on dark matter halos represented by galaxy groups selected from surveys of galaxies at high redshift. We test the performance of this method on halos in N-body simulations, and find it can correctly identify more than 85% of the true proto-clusters with $\gtrsim$ 95% purity and with mass estimates typical within 0.25 dex from their true values. We show how the information provided by the proto-clusters can be used to link galaxies in present-day clusters of galaxies with their high redshift progenitors. Our tests show that the proto-clusters identified by our method can recover reliably the progenitor stellar mass distribution of galaxies, thereby providing an avenue to investigate the formation and evolution of present-day galaxy clusters and their member galaxies.

  • Evaluating the origins of the secondary bias based on the correlation of halo properties with the linear density field

    分类: 天文学 >> 天文学 提交时间: 2023-02-19

    摘要: Using two sets of large $N$-body simulations, we study the origin of the correlations of halo assembly time ($z_{\rm f}$), concentration ($v_{\rm max}/v_{\rm 200}$) and spin ($\lambda$) with the large-scale evolved density field at given halo mass, i.e. the secondary bias. We find that the secondary bias is the secondary effect of the correlations of halo properties with the linear density estimated at the same comoving scale. Using the linear density on different scales, we find two types of correlations. The internal correlation, which reflects the correlation of halo properties with the mean linear over-density $\delta_{\rm L}$ within the halo Lagrangian radius $R_{\rm L}$, is positive for both $z_{\rm f}$ and $v_{\rm max}/v_{\rm 200}$, and negative for $\lambda$. The external correlation, which describes the correlation of halo properties with linear overdensity at $R>R_{\rm L}$ for given $\delta_{\rm L}$, shows trends opposite to the internal correlation. Both of the external and internal correlations depend only weakly on halo mass, indicating a similar origin for halos of different masses. Our findings offer a transparent perspective on the origin of the secondary bias. The secondary bias can be largely explained by the competition of the external and internal correlations together with the correlation of the linear density field on different scales. These two types of correlations combined can establish the complex halo-mass dependence of the secondary bias observed in the simulations.

  • Anisotropy and characteristic scales in halo density gradient profiles

    分类: 天文学 >> 天文学 提交时间: 2023-02-19

    摘要: We use a large N-body simulation to study the characteristic scales in the density gradient profiles in and around halos with masses ranging from $10^{12}$ to $10^{15} h^{-1}{\rm M_\odot}$. We investigate the profiles separately along the major (T_1) and minor (T_3) axes of the local tidal tensor and how the characteristic scales depend on halo mass, formation time, and environment. We find two kinds of prominent characteristic features in the gradient profiles, a deep `valley' and a prominent `peak'. We use the Gaussian Process Regression to fit the gradient profiles and identify the local extrema to determine the scales associate with these features. Around the valley, we identify three types of distinct local minima, corresponding to caustics of particles orbiting around halos. The appearance and depth of the three caustics depend significantly on the direction defined by the local tidal field, formation time and environment of halos. The first caustic is located at a radius r>0.8R_{200}, corresponding to the splashback feature, and is dominated by particles at their first apocenter after infall. The second and third caustics, around 0.6R_{200} and 0.4R_{200} respectively, can be determined reliably only for old halos. The first caustic is always the most prominent feature along T_3, but may not be the case along T_1 or in azimuthally-averaged profiles, suggesting that caution must be taken when using averaged profiles to investigate the splashback radius. We find that the splashback feature is approximately isotropic when proper separations are made between the first and the other caustics. We also identify a peak feature located at $\sim$ 2.5R_{200} in the density gradient profile. This feature is the most prominent along T_1 and is produced by mass accumulations from the structure outside halos. We also discuss the origins of these features and their observational implications.

  • Conditional HI mass functions and the HI-to-halo mass relation in the local Universe

    分类: 天文学 >> 天文学 提交时间: 2023-02-19

    摘要: We present a new HI mass estimator which relates the HI-to-stellar mass ratio to four galaxy properties: stellar surface mass density, color index $u-r$, stellar mass and concentration index, with the scatter of individual galaxies around the mean HI mass modeled with a Gaussian distribution. We calibrate the estimator using the xGASS sample, including both HI detection and non-detection, and constrain the model parameters through Bayesian inferences. Tests with mock catalogs demonstrate that our estimator provides unbiased HI masses for optical samples like the SDSS, thus suitable for statistical studies of HI gas contents in galaxies and dark matter halos. We apply our estimator to the SDSS spectroscopic sample to estimate the local HI mass function (HIMF), the conditional HI mass function (CHIMF) in galaxy groups and the HI-halo mass (HIHM) relation. Our HIMF agrees with the ALFALFA measurements at $M_{HI}\gtrsim 5\times 10^9M_{\odot}$, but with higher amplitude and a steeper slope at lower masses. We show that this discrepancy is caused primarily by the cosmic variance which is corrected for the SDSS sample but not for the ALFALFA. The CHIMFs for all halo masses can be described by a single Schechter function, and this is true for red, blue and satellite galaxies. For central galaxies the CHIMFs show a double-Gaussian profile, with the two components contributed by the red and blue galaxies, respectively. The total HI mass in a group increases monotonically with halo mass. The HI mass of central galaxies in galaxy groups increases rapidly with halo mass only at $M_h\lesssim10^{12}M_{\odot}$, while the mass dependence becomes much weaker at higher halo masses. The observed HI-halo mass relation is not reproduced by current hydrodynamic simulations and semi-analytic models of galaxy formation.

  • Massive Star-Forming Galaxies Have Converted Most of Their Halo Gas into Stars

    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.

  • MAHGIC: A Model Adapter for the Halo-Galaxy Inter-Connection

    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.

  • Hosts and triggers of AGNs in the Local Universe

    分类: 天文学 >> 天文学 提交时间: 2023-02-19

    摘要: Based on the spectroscopic and shear catalogs for SDSS galaxies in the local Universe, we compare optically-selected active galactic nuclei (AGNs) with control star-forming and quiescent galaxies on galactic, inter-halo and larger scales. We find that AGNs are preferentially found in two specific stages of galaxy evolution: star-burst and `green valley' phases, and that the stellar population of their host galaxies is quite independent of stellar mass, different from normal galaxies. Combining galaxy-galaxy lensing and galaxy clustering on large scales, we measure the mass of AGN host halos. The typical halo mass is about $10^{12}h^{-1}\rm M_{\odot}$, similar to the characteristic mass in the stellar mass-halo mass relation (SHMR). For given stellar mass, AGN host galaxies and star-forming galaxies share the same SHMR, while quiescent galaxies have more massive halos. Clustering analysis on halo scales reveals that AGNs are surrounded by a larger number of satellites (with stellar mass down to 1/1000 of the mass of the central galaxy) than star-forming galaxies, and that galaxies with larger stellar velocity dispersion have more satellites. The number of satellites also increase with halo mass, reaching unity around $10^{12}h^{-1}\rm M_{\odot}$. Our results suggest a scenario, in which the interaction of the central galaxy with the satellites triggers an early episode of star burst and AGN activities, followed by multiple AGN cycles driven by the non-axisymmetric structure produced by the interaction. The feedback from the starburst and AGN reduces the amount of cold gas for fueling the central black hole, producing a characteristic halo mass scale, $\sim 10^{12}h^{-1}\rm M_{\odot}$, where the AGN fraction peaks.

  • Shock-induced stripping of satellite ISM/CGM in IllustrisTNG clusters at $z\sim0$

    分类: 天文学 >> 天文学 提交时间: 2023-02-19

    摘要: Using the IllustrisTNG simulation, we study the interaction of large-scale shocks with the circumgalactic medium (CGM) and interstellar medium (ISM) of star-forming (SF) satellite galaxies in galaxy clusters. These shocks are usually produced by mergers and massive accretion. Our visual inspection shows that approximately half of SF satellites have encountered shocks in their host clusters at $z\leq0.11$. After a satellite crosses a shock front and enters the postshock region, the ram pressure on it is boosted significantly. Both the CGM and ISM can be severely impacted, either by striping or compression. The stripping of the ISM is particularly important for low-mass galaxies with $\log (M_{*}/M_{\odot})<10$ and can occur even in the outskirts of galaxy clusters. In comparison, satellites that do not interact with shocks lose their ISM only in the inner regions of clusters. About half of the ISM is stripped within about 0.6 Gyr after it crosses the shock front. Our results show that shock-induced stripping plays an important role in quenching satellite galaxies in clusters.

  • Groups and protocluster candidates in the CLAUDS and HSC-SSP joint deep surveys

    分类: 天文学 >> 天文学 提交时间: 2023-02-19

    摘要: Using the extended halo-based group finder developed by Yang et al. (2021), which is able to deal with galaxies via spectroscopic and photometric redshifts simultaneously, we construct galaxy group and candidate protocluster catalogs in a wide redshift range ($0 2.0$. By checking the galaxy number distributions within a $5-7\ h^{-1}\mathrm{Mpc}$ projected separation and a redshift difference $\Delta z \le 0.1$ around those richest groups at redshift $z>2$, we identified a list of 761, 343 and 43 protocluster candidates in the redshift bins $2\leq z<3$, $3\leq z<4$ and $z \geq 4$, respectively. In general, these catalogs of galaxy groups and protocluster candidates will provide useful environmental information in probing galaxy evolution along the cosmic time.

  • ELUCID VII: Using Constrained Hydro Simulations to Explore the Gas Component of the Cosmic Web

    分类: 天文学 >> 天文学 提交时间: 2023-02-19

    摘要: Using reconstructed initial conditions in the SDSS survey volume, we carry out constrained hydrodynamic simulations in three regions representing different types of the cosmic web: the Coma cluster of galaxies; the SDSS great wall; and a large low-density region at $z\sim 0.05$. These simulations, which include star formation and stellar feedback but no AGN formation and feedback, are used to investigate the properties and evolution of intergalactic and intra-cluster media. About half of the warm-hot intergalactic gas is associated with filaments in the local cosmic web. Gas in the outskirts of massive filaments and halos can be heated significantly by accretion shocks generated by mergers of filaments and halos, respectively, and there is a tight correlation between gas temperature and the strength of the local tidal field. The simulations also predict some discontinuities associated with shock fronts and contact edges, which can be tested using observations of the thermal SZ effect and X-rays. A large fraction of the sky is covered by Ly$\alpha$ and OVI absorption systems, and most of the OVI systems and low-column density HI systems are associated with filaments in the cosmic web. The constrained simulations, which follow the formation and heating history of the observed cosmic web, provide an important avenue to interpret observational data. With full information about the origin and location of the cosmic gas to be observed, such simulations can also be used to develop observational strategies.

  • A Conditional Abundance Matching Method of Extending Simulated Halo Merger Trees to Resolve Low-Mass Progenitors and Sub-halos

    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.

  • A Conditional Abundance Matching Method of Extending Simulated Halo Merger Trees to Resolve Low-Mass Progenitors and Sub-halos

    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.

  • Conditional HI mass functions and the HI-to-halo mass relation in the local Universe

    分类: 天文学 >> 天文学 提交时间: 2023-02-19

    摘要: We present a new HI mass estimator which relates the HI-to-stellar mass ratio to four galaxy properties: stellar surface mass density, color index $u-r$, stellar mass and concentration index, with the scatter of individual galaxies around the mean HI mass modeled with a Gaussian distribution. We calibrate the estimator using the xGASS sample, including both HI detection and non-detection, and constrain the model parameters through Bayesian inferences. Tests with mock catalogs demonstrate that our estimator provides unbiased HI masses for optical samples like the SDSS, thus suitable for statistical studies of HI gas contents in galaxies and dark matter halos. We apply our estimator to the SDSS spectroscopic sample to estimate the local HI mass function (HIMF), the conditional HI mass function (CHIMF) in galaxy groups and the HI-halo mass (HIHM) relation. Our HIMF agrees with the ALFALFA measurements at $M_{HI}\gtrsim 5\times 10^9M_{\odot}$, but with higher amplitude and a steeper slope at lower masses. We show that this discrepancy is caused primarily by the cosmic variance which is corrected for the SDSS sample but not for the ALFALFA. The CHIMFs for all halo masses can be described by a single Schechter function, and this is true for red, blue and satellite galaxies. For central galaxies the CHIMFs show a double-Gaussian profile, with the two components contributed by the red and blue galaxies, respectively. The total HI mass in a group increases monotonically with halo mass. The HI mass of central galaxies in galaxy groups increases rapidly with halo mass only at $M_h\lesssim10^{12}M_{\odot}$, while the mass dependence becomes much weaker at higher halo masses. The observed HI-halo mass relation is not reproduced by current hydrodynamic simulations and semi-analytic models of galaxy formation.