arXiv subjects

Paramita Barai

Publications and source records attributed to Paramita Barai.

At least 19 recordsLinked to original sources

arXiv2026

Gas Accretion versus BH Merger driven Growth Modes of Supermassive Black Holes and Implications for the Little Red Dots

We investigate the growth of central supermassive black holes in galaxies, aiming to distinguish between gas accretion versus BH merger-driven growth modes. By performing and analysing cosmological hydrodynamical simulations of $(50 ~ {\rm Mpc})^3$ comoving boxes, we also study how the BH feedback parameters affect the coevolution between SMBHs and their host galaxies. Starting as $10^5 M_{\odot}$ seeds, we find that the BHs grow initially via BH mergers to $\sim 10^7 M_{\odot}$. Gas accretion onto the BHs is initially low, then increases with time, and reaches the Eddington rate after $7-9$ Gyrs. The BHs then undergo very fast growth via efficient gas accretion over a period of $600 - 700$ Myr, when the BH mass increases $10^2 - 10^3$ times, causing their predominant growth from $10^7 M_{\odot}$ to $(10^9 - 10^{10}) M_{\odot}$. Taking into account the cosmological gas inflows and outflows, SMBHs do not grow to more than $10^{10} M_{\odot}$ by $z=0$, because of gas depletion from galaxy centers driven by AGN feedback. In terms of SMBH - host galaxy coevolution along the $M_{\rm BH} - M_{\star}$ relation, we find that they initially lie below and thereby move upward toward the relation. We make some physical implications of the growth of high-$z$ Little Red Dots recently observed by JWST: the normal-mass SMBHs had predominantly undergone BH merger driven evolution, whereas the overmassive BHs underwent periods of Eddington-limited or super-Eddington bursts of gas accretion.

astro-ph.GA↗

arXiv2025

The evolution of obscured AGN across cosmic time -- A large quasar survey for the 2040s

We propose a large quasar demographic optical multi-object spectroscopic (MOS) survey targeting over 50 million AGN candidates up to the highest redshifts possible in the optical (z~6.5), with repeat visits, using a variety of selection criteria available by 2040. A large MOS survey combining all AGN selection methods is the only way to unify a diverse range of different obscured AGN populations within a single, variability- and spectroscopy-based framework, rather than as disjoint classes selected by different methods.

astro-ph.GA↗

arXiv2024

Exploring the evolution of a dwarf spheroidal galaxy with SPH simulations: I. Stellar feedback

A fundamental question regarding the evolution of dwarf spheroidal galaxies is the identification of the key physical mechanisms responsible for gas depletion. Here, we focus on the study of stellar feedback in isolated dwarf spheroidal galaxies, by performing numerical simulations using a modified version of the SPH code GADGET-3. The Milky Way satellite Leo II (PGC 34176) in the Local Group was considered as our default model dwarf galaxy. The parameter space for the stellar feedback models was explored to match observational constraints of Leo II, such as residual gas mass, total mass within the tidal radius, star formation history, final stellar mass, stellar ages and metallicity. Additionally, we examined the impact of the binary fraction of stars, initial mass function, dark matter halo mass and initial gas reservoir. Many simulations revealed recent star formation quenching due to stellar feedback. In general, the gas depletion, expected star formation history, total mass of stars and total mass within the tidal radius were adequately reproduced in the simulations when compared to observational estimates. However, there were discrepancies in the distribution of stellar ages and metallicities, which suggested that the cosmic gas infall would play a more complex role in our dwarf spheroidal galaxy than captured by a monolithic infall scenario. Our results suggest that currently quenched dwarf galaxies may not necessarily need to evolve within clusters or groups, and that stellar feedback alone could be a sufficient factor in shaping at least some of these galaxies as we observe them today.

astro-ph.GA↗

arXiv2024

Design of an Analog Memory Cell in 0.25 micron CMOS process

CMOS VLSI technology is the most dominant integration methodology prevailing in the world today. Various signal-processing blocks are made using analog or digital design techniques in MOS VLSI. An important component is the Memory unit used to store data. In the project a memory cell has been built up using analog design method. A capacitor is used as the basic storage device. The main idea behind analog memory is that the analog value of the charge or voltage stored in the capacitor is the data stored. So the dielectric quality of the capacitor becomes important here to determine how effectively it can store some charge. Analog memory is a trade off between hardware cost, chip area and accuracy or quality of storage. The circuit of analog memory cell was developed starting from the idea that required voltage will be stored in a capacitor and MOS transistors were used as switches. A given technology of integration was used and hence the dielectric property of the capacitor was fixed. By suitable circuit configuration the analog voltage value was written to the capacitor, read out when required and the charge loss was also refreshed. The results obtained are as given in the thesis.

cs.OH↗

arXiv2023

Probing $z \gtrsim 6$ massive black holes with gravitational waves

We investigate the coalescence of massive black hole ($M_{\rm BH}\gtrsim 10^{6}~\rm M_{\odot}$) binaries (MBHBs) at $6 3 σ$) overdense regions ($M_h\sim 10^{12}~\rm M_{\odot}$ dark matter halos at $z = 6$) of the Universe. We first analyse the impact of different resolutions and AGN feedback prescriptions on the merger rate, assuming instantaneous mergers. Then, we compute the halo bias correction factor due to the overdense simulated region. Our simulations predict merger rates that range between 3 - 15 $\rm yr^{-1}$ at $z\sim 6$, depending on the run considered, and after correcting for a bias factor of $\sim 20-30$. For our fiducial model, we further consider the effect of delay in the MBHB coalescence due to dynamical friction. We find that 83 per cent of MBHBs will merge within the Hubble time, and 21 per cent within 1 Gyr, namely the age of the Universe at $z > 6$. We finally compute the expected properties of the gravitational wave (GW) signals and find the fraction of LISA detectable events with high signal-to-noise ratio (SNR $>$ 5) to range between 66-69 per cent. However, identifying the electro-magnetic counterpart of these events remains challenging due to the poor LISA sky localization that, for the loudest signals ($\mathcal M_c\sim 10^6~\rm M_{\odot}$ at $z=6$), is around 10 $\rm deg^2$.

astro-ph.GA↗

arXiv2022

Enhanced star formation in $z\sim6$ quasar companions

Quasars powered by supermassive black holes (MBH, $>10^8~M_{\odot}$) at $z\sim 6$ are predicted to reside in cosmic over-dense regions. However, observations so far could not confirm this expectation due to limited statistics. The picture is further complicated by the possible effects of quasar outflows (i.e. feedback) that could either suppress or stimulate the star formation rate (SFR) of companion galaxies, thus modifying the expected bias. Here we quantify feedback effects on the properties and detectability of companions by comparing cosmological zoom-in simulations of a quasar in which feedback is either included or turned-off. With respect to the no-feedback case, companions (a) directly impacted by the outflow have their SFR increased by a factor $2-3$, and (b) tend to be more massive. Both effects shift the [CII]158$μ$m and UV luminosity functions toward brighter magnitudes. This leads us to conclude that quasar feedback slightly increases the effective quasar bias, boosting the number density of observable quasar companions, in agreement with what has been found around the brightest quasars of recent ALMA [CII] surveys. Deeper observations performed with JWST and/or ALMA will improve the statistical significance of this result by detecting a larger number of fainter quasar companions.

astro-ph.GA↗

arXiv2019

Intermediate-Mass Black Hole Growth and Feedback in Dwarf Galaxies at High Redshifts

Intermediate-mass black holes (IMBHs: masses between $100 - 10^{6} M_{\odot}$) historically comprise of an elusive population compared to stellar-mass and supermassive BHs. Recently IMBHs have started to be observed at the centers of low-mass galaxies. We perform cosmological hydrodynamical simulations of $(2 h^{-1} ~ {\rm Mpc})^3$ comoving boxes and investigate the growth and feedback of central IMBHs in dwarf galaxies (DGs). The earliest BHs appear at $z \sim 18 - 25$, and grow thereafter by accreting gas and by merger with other BHs. We find that, starting from $10^{2} M_{\odot}$, it is possible to build up IMBHs of a few$\times 10^{5} - 10^{6} M_{\odot}$ by $z = 5$, when the BHs are seeded in halos less massive than $4 \times 10^{7} M_{\odot}$. The BH accretion rates increase with time, and reaches $\dot{M}_{\rm BH} = (0.2 - 0.8) \dot{M}_{\rm Edd}$ for the massive IMBHs by $z = 4$. The star formation rate density (SFRD) evolution of the DGs (stellar mass $10^{5} - 10^{8} M_{\odot}$) has a peak plateau between $z = 4 - 6$. Star formation is quenched between $z = 9 - 4$. The SFRD is reduced by factors up to $3$, when the BHs have grown to a few times $10^5 M_{\odot}$. Even in the presence of stronger SN-driven mass ejection, the BHs continue to grow up to $z \sim 6$, sustained by gas inflows driven by galaxy mergers and interactions in a cosmological environment. Our conclusions, based on numerical simulation results, support the scenario that early feedback from IMBHs in gas-rich DGs at $z = 5 - 8$ can potentially solve several anomalies in the DG mass range within the concordance $Λ$CDM cosmological scenario (Silk 2017). Our results suggest that IMBHs at DG centers grow faster than their host galaxies in the early Universe, and the resulting BH feedback turns the DGs and the BHs dormant.

astro-ph.GA↗

arXiv2019

Supermassive and Intermediate-Mass Black Hole Growth at Galaxy Centers and Resulting Feedback using Cosmological Simulations

Accretion of matter onto central Black Holes (BHs) in galaxies liberates enormous amounts of feedback energy, which influence the formation and evolution of structures, affecting the environment from pc to Mpc scales. These BHs are usually Supermassive BHs (SMBHs: mass $\geq 10^6 M_{\odot}$) existing at the centers of active galactic nuclei (AGN), which are widely observed through their multi-wavelength emission at all cosmic epochs. The SMBH energy output is often observed as powerful AGN outflows in a wide variety of forms. Relatively recently, Intermediate-Mass BHs (IMBHs: mass = $100 - 10^6 M_{\odot}$) have started to be observed hosted in Dwarf Galaxy (DG) centers. Some of the central IMBHs in DGs show signatures of activity in the form of low-luminosity AGN. We have performed Cosmological Hydrodynamical Simulations to probe SMBHs in high-z quasars (Barai et al. 2018), and IMBHs in DGs (Barai & de Gouveia Dal Pino 2019). Our simulations employ the 3D TreePM SPH code GADGET-3, and include metal cooling, star formation, chemical enrichment, stellar evolution, supernova feedback, AGN accretion and feedback. Analyzing the simulation output in post-processing, we investigate the growth of the first IMBHs, and the growth of the first SMBHs, their impact on star-formation, as well as their co-evolution with the respective host galaxies. We quantify the impact of SMBHs and IMBHs on their host galaxies, especially the effects on quenching star-formation. We also study the corresponding BH outflow properties.

astro-ph.GA↗

arXiv2018

Intermediate-Mass Black Hole Feedback in Dwarf Galaxies: a View from Cosmological Simulations

Black holes are usually observed to be of stellar-mass or supermassive. By natural extension, there should be a population of Intermediate-Mass Black Holes (IMBHs: with mass between $100$ to $10^6 M_{\odot}$) in the Universe; which has started to been observed. An exciting claim has been made recently by Silk (2017): that early feedback by IMBHs in gas-rich dwarf galaxies at $z=5-8$, can potentially solve multiple dwarf galaxy problems within the $Λ$-cold-dark-matter cosmology. We are performing Cosmological Hydrodynamical Simulations of $(2 Mpc)^3$ volumes, starting from $z=100$, to test the case for IMBHs in Dwarf Galaxies. Black holes of mass $1000 M_{\odot}$ are seeded inside halos when they reach a mass of $10^7 M_{\odot}$. The black holes grow by accretion of gas from their surroundings and by merger with other black holes, and consequently eject feedback energy. We analyze the simulation output in post-processing to study the growth of the first IMBHs, and their impact on star-formation. Our conclusions, based on numerical simulation results, support the phenomenological ideas made by Silk (2017). IMBHs at the centers of dwarf galaxies can be a strong source of feedback to quench star-formation and generate outflows. At the same time, these IMBHs form the missing link between stellar-mass and supermassive BHs.

astro-ph.GA↗

arXiv2018

Large-Scale Diffuse Intergalactic Magnetic Fields Constraints with the Cherenkov Telescope Array

Magnetic fields of the order of $μ$-Gauss are observationally detected in galaxies and galaxy clusters, which can be (at least) in part originated by the amplification of much weaker primordial seed fields. These fields should be carried out by strong galactic outflows, magnetically enriching the InterGalactic Medium (IGM). However direct observation of magnetic fields in the IGM is scarce. This talk will give a review of how Intergalactic Magnetic Field (IGMF) can be constrained using gamma-ray observations. High-energy TeV photons emitted by distant blazars can interact with the cosmic extragalactic optical/infrared/microwave background light, producing electron-positron pairs, and initiating electromagnetic cascades in the IGM. The charged component of these cascades is deflected by IGMFs, thereby reducing the observed point-like TeV flux, and creating an extended image in the GeV energy range, which can potentially be detected with $γ$-ray telescopes (Fermi-LAT, HESS, CTA). Studies (e.g., Neronov & Vovk 2010, Dolag et al. 2011) have put lower limits on the IGMF strength of the order of $10^{-16} - 10^{-15} G$, and filling factors of $60\%$. This talk will describe the constraints which the Cherenkov Telescope Array sensitivity is expected to give (CTA Consortium 2018).

astro-ph.HE↗

arXiv2017

Quasar outflows at $z \geq 6$: the impact on the host galaxies

We investigate quasar outflows at $z \geq 6$ by performing zoom-in cosmological hydrodynamical simulations. By employing the SPH code GADGET-3, we zoom in the $2 R_{200}$ region around a $2 \times 10^{12} M_{\odot}$ halo at $z = 6$, inside a $(500 ~ {\rm Mpc})^3$ comoving volume. We compare the results of our AGN runs with a control simulation in which only stellar/SN feedback is considered. Seeding $10^5 M_{\odot}$ BHs at the centers of $10^{9} M_{\odot}$ halos, we find the following results. BHs accrete gas at the Eddington rate over $z = 9 - 6$. At $z = 6$, our most-massive BH has grown to $M_{\rm BH} = 4 \times 10^9 M_{\odot}$. Fast ($v_{r} > 1000$ km/s), powerful ($\dot{M}_{\rm out} \sim 2000 M_{\odot}$/yr) outflows of shock-heated low-density gas form at $z \sim 7$, and propagate up to hundreds kpc. Star-formation is quenched over $z = 8 - 6$, and the total SFR (SFR surface density near the galaxy center) is reduced by a factor of $5$ ($1000$). We analyse the relative contribution of multiple physical process: (i) disrupting cosmic filamentary cold gas inflows, (ii) reducing central gas density, (iii) ejecting gas outside the galaxy; and find that AGN feedback has the following effects at $z = 6$. The inflowing gas mass fraction is reduced by $\sim 12 \%$, the high-density gas fraction is lowered by $\sim 13 \%$, and $\sim 20 \%$ of the gas outflows at a speed larger than the escape velocity ($500$ km/s). We conclude that quasar-host galaxies at $z \geq 6$ are accreting non-negligible amount of cosmic gas, nevertheless AGN feedback quenches their star formation dominantly by powerful outflows ejecting gas out of the host galaxy halo.

astro-ph.GA↗

arXiv2016

Kinetic AGN Feedback Effects on Cluster Cool Cores Simulated using SPH

We implement novel numerical models of AGN feedback in the SPH code GADGET-3, where the energy from a supermassive black hole (BH) is coupled to the surrounding gas in the kinetic form. Gas particles lying inside a bi-conical volume around the BH are imparted a one-time velocity (10,000 km/s) increment. We perform hydrodynamical simulations of isolated cluster (total mass 10^14 /h M_sun), which is initially evolved to form a dense cool core, having central T<10^6 K. A BH resides at the cluster center, and ejects energy. The feedback-driven fast wind undergoes shock with the slower-moving gas, which causes the imparted kinetic energy to be thermalized. Bipolar bubble-like outflows form propagating radially outward to a distance of a few 100 kpc. The radial profiles of median gas properties are influenced by BH feedback in the inner regions (r<20-50 kpc). BH kinetic feedback, with a large value of the feedback efficiency, depletes the inner cool gas and reduces the hot gas content, such that the initial cool core of the cluster is heated up within a time 1.9 Gyr, whereby the core median temperature rises to above 10^7 K, and the central entropy flattens. Our implementation of BH thermal feedback (using the same efficiency as kinetic), within the star-formation model, cannot do this heating, where the cool core remains. The inclusion of cold gas accretion in the simulations produces naturally a duty cycle of the AGN with a periodicity of 100 Myr.

astro-ph.GA↗

arXiv2014

Black Hole spin dependence of general relativistic multi-transonic accretion close to the horizon

We introduce a novel formalism to investigate the role of the spin angular momentum of astrophysical black holes in influencing the behaviour of low angular momentum general relativistic accretion. We propose a metric independent analysis of axisymmetric general relativistic flow, and consequently formulate the space and time dependent equations describing the general relativistic hydrodynamic accretion flow in the Kerr metric. The associated stationary critical solutions for such flow equations are provided and the stability of the stationary transonic configuration is examined using an elegant linear perturbation technique. We examine the properties of infalling material for both prograde and retrograde accretion as a function of the Kerr parameter at extremely close proximity to the event horizon. Our formalism can be used to identify a new spectral signature of black hole spin, and has the potential of performing the black hole shadow imaging corresponding to the low angular momentum accretion flow.

astro-ph.HE↗

arXiv2014

Galactic outflow and diffuse gas properties at z>=1 using different baryonic feedback models

We measure and quantify properties of galactic outflows and diffuse gas at $z \geq 1$ in cosmological hydrodynamical simulations. Our novel sub-resolution model, MUPPI, implements supernova feedback using fully local gas properties, where the wind velocity and mass loading are not given as input. We find the following trends at $z = 2$ by analysing central galaxies having a stellar mass higher than $10^{9} M_{\odot}$. The outflow velocity and mass outflow rate ($\dot{M}_{\rm out}$) exhibit positive correlations with galaxy mass and with the star formation rate (SFR). However, most of the relations present a large scatter. The outflow mass loading factor ($η$) is between $0.2 - 10$. The comparison Effective model generates a constant outflow velocity, and a negative correlation of $η$ with halo mass. The number fraction of galaxies where outflow is detected decreases at lower redshifts, but remains more than $80 \%$ over $z = 1 - 5$. High SF activity at $z \sim 2 - 4$ drives strong outflows, causing the positive and steep correlations of velocity and $\dot{M}_{\rm out}$ with SFR. The outflow velocity correlation with SFR becomes flatter at $z = 1$, and $η$ displays a negative correlation with halo mass in massive galaxies. Our study demonstrates that both the MUPPI and Effective models produce significant outflows at $\sim 1 / 10$ of the virial radius; at the same time shows that the properties of outflows generated can be different from the input speed and mass loading in the Effective model. Our MUPPI model, using local properties of gas in the sub-resolution recipe, is able to develop galactic outflows whose properties correlate with global galaxy properties, and consistent with observations.

astro-ph.GA↗

arXiv2014

Major Cluster Mergers and the Location of the Brightest Cluster Galaxy

Using a large N-body cosmological simulation combined with a subgrid treatment of galaxy formation, we study the formation and evolution of the galaxy and cluster population in a comoving volume (100 Mpc)^3 in a LCDM universe. At z = 0, our computational volume contains 1788 clusters with mass M_cl > 1.1x10^12 Msun, including 18 massive clusters with M_cl > 10^14 Msun. It also contains 1 088 797 galaxies with mass M_gal > 2x10^9 Msun and luminosity L > 9.5x10^5 Lsun. For each cluster, we identified the brightest cluster galaxy (BCG). We then computed the fraction f_BNC of clusters in which the BCG is not the closest galaxy to the center of the cluster in projection, and the ratio Dv/s, where Dv is the difference in radial velocity between the BCG and the whole cluster, and s is the radial velocity dispersion of the cluster. f_BNC increases from 0.05 for low-mass clusters (M_cl ~ 10^12 Msun) to 0.5 for high-mass ones (M_cl > 10^14 Msun), with no dependence on cluster redshift. The values of Dv/s vary from 0 to 1.8. These results are consistent with previous observational studies, and indicate that the central galaxy paradigm, which states that the BCG should be at rest at the center of the cluster, is usually valid, but exceptions are too common to be ignored. Analysis of the merger trees for the 18 most massive clusters in the simulation reveals that 16 of these clusters have experienced major mergers in the past. These mergers leave each cluster in a non-equilibrium state, but eventually the cluster settles into an equilibrium configuration, unless it is disturbed by another major merger. We found evidence that these mergers are responsible for the off-center positions and peculiar velocities of some BCGs. Our results thus support the merging-group scenario, in which some clusters form by the merger of smaller groups in which the galaxies have already formed.

astro-ph.CO↗

arXiv2014

Simulated star formation rate functions at z~4-7, and the role of feedback in high-z galaxies

We study the role of feedback from supernovae and black holes in the evolution of the star formation rate function (SFRF) of z~4-7 galaxies. We use a new set of cosmological hydrodynamic simulations, ANGUS (AustraliaN GADGET-3 early Universe Simulations), run with a modified and improved version of the parallel TreePM-smoothed particle hydrodynamics code GADGET-3 called P-GADGET3(XXL), that includes a self-consistent implementation of stellar evolution and metal enrichment. In our simulations both Supernova (SN) driven galactic winds and Active Galactic Nuclei (AGN) act simultaneously in a complex interplay. The SFRF is insensitive to feedback prescription at z>5, meaning that it cannot be used to discriminate between feedback models during reionisation. However, the SFRF is sensitive to the details of feedback prescription at lower redshift. By exploring different SN driven wind velocities and regimes for the AGN feedback, we find that the key factor for reproducing the observed SFRFs is a combination of "strong" SN winds and early AGN feedback in low mass galaxies. Conversely, we show that the choice of initial mass function and inclusion of metal cooling have less impact on the evolution of the SFRF. When variable winds are considered, we find that a non-aggressive wind scaling is needed to reproduce the SFRFs at z>4. Otherwise, the amount of objects with low SFRs is greatly suppressed and at the same time winds are not effective enough in the most massive systems.

astro-ph.CO↗

arXiv2013

Kinetic or thermal AGN feedback in simulations of isolated and merging disk galaxies calibrated by the M-sigma relation

(Abridged) We investigate two modes of coupling the feedback energy from a central AGN to the neighboring gas in galaxy simulations: kinetic - velocity boost, and thermal - heating. We formulate kinetic feedback models for energy-driven wind (EDW) and momentum-driven wind (MDW), using two free parameters: feedback efficiency epsilon_f, and AGN wind velocity v_w. A novel numerical algorithm is implemented in the SPH code GADGET-3, to prevent the expansion of a hole in the gas distribution around the BH. We perform simulations of isolated evolution and merger of disk galaxies, of Milky-Way mass as well as lower and higher masses. We find that in the isolated galaxy BH kinetic feedback generates intermittent bipolar jet-like gas outflows. We infer that current prescriptions for BH subgrid physics in galaxy simulations can grow the BH to observed values even in an isolated disk galaxy. The BH growth is enhanced in a galaxy merger. Comparing the [M_BH - sigma_star] relation obtained in our simulations with observational data, we conclude that it is possible to find parameter sets for a fit in all the models, except for the case with MDW feedback in a galaxy merger, in which the BH is always too massive. The BH thermal feedback implementation of Springel, Di Matteo & Hernquist (2005) within the multiphase star-formation model is found to have negligible impact on gas properties; and the effect claimed in all previous studies is attributed to gas depletion around the BH by the creation of an artificial hole. The BH mass accretion rate in our simulations exhibit heavy fluctuations. The star formation rate is quenched with feedback by removal of gas. The CGM gas at galactocentric distances (20 - 100)/h kpc are found to give the best metallicity observational diagnostic to distinguish between BH models.

astro-ph.CO↗

arXiv2013

Galactic Winds in Cosmological Simulations of the Circumgalactic Medium

(Abridged) We explore new observationally-constrained sub-resolution models of galactic outflows and investigate their impact on the circumgalactic medium (CGM) over redshifts z = 2 - 4. We perform cosmological hydrodynamic simulations, including star formation, chemical enrichment, and four cases of SNe-driven outflows: no wind (NW), an energy-driven constant velocity wind (CW), a radially varying wind (RVWa) where the outflow velocity has a positive correlation with galactocentric distance (r), and a RVW with additional dependence on halo mass (RVWb). Overall, we find that the outflows expel metal-enriched gas away from galaxies, significantly quench star formation, and enrich the CGM. At z = 2, the radial profiles of gas properties around galaxy centers are most sensitive to the choice of the wind model for halo masses (10^9 - 10^11) M_sun. We infer that the RVWb model is similar to the NW case, except that it substantially enriches the CGM: the carbon metallicity (Z_C) is 10 times higher in RVWb than in NW at r > R_200; and the warm gas of 10^4 - 10^5 K and delta < 100 is enriched to 50 times higher than in NW. We also find that the impact of models CW and RVWa are similar, with the following differences. RVWa causes a greater suppression of star formation rate at z < 5, and has a higher fraction of low-density (delta < 10), warm-hot (10^4 - 10^6 K) gas than in CW. Outflows in CW produce a higher and earlier enrichment of some IGM phases than RVWa. By visual inspection, we note that the RVWa model shows more pronounced bipolar outflows and galactic disks. We present fitting formulae for [Z_C-delta] and [Z_C-r], also for the abundance of CIV as a function of r. We predict observational diagnostics to distinguish between different outflow scenarios: Z_C of the CGM gas at r = (30 - 300) kpc/h comoving, and CIV fraction of the inner gas at r < (4 - 5) kpc/h comoving.

astro-ph.CO↗