arXiv subjects

Aditya Manuwal

Publications and source records attributed to Aditya Manuwal.

10 recordsLinked to original sources

arXiv2026

Asymmetries in spatially unresolved 21-cm emission line profiles of isolated galaxies

The origin of asymmetry in the ${\rm H}\,{\scriptsize{\rm I}}$ of galaxies remains an elusive problem, largely due to the difficulties associated with distinguishing between its secular and external contributors. We have compiled a sample of local isolated galaxies from the UNAM-KIAS and the latest AMIGA samples with near-complete beam coverage and robust estimates of ${\rm H}\,{\scriptsize{\rm I}}$ line asymmetry. The ${\rm H}\,{\scriptsize{\rm I}}$ measurements are based on single-dish spectra sourced from five surveys: ${\rm H}\,{\scriptsize{\rm I}}$-MaNGA, NIBLES, KLUN, ALFALFA, and xGASS. Our galaxies tend to be late-type, star-forming centrals at all masses but exhibit slightly lower specific star formation rates (sSFRs) and higher ${\rm H}\,{\scriptsize{\rm I}}$ contents than expected. The latter is likely driven by lower star formation efficiency, weaker outflows, and additionally, higher accretion rate of gas onto the galaxy at $M_\star\lesssim 10^{10.3}\,\mathrm{M}_\odot$. AMIGA, however, shows systematically higher ${\rm H}\,{\scriptsize{\rm I}}$ masses than UNAM-KIAS, which we attribute to higher local densities probed by the latter. Furthermore, both samples show bar frequencies similar to normal spirals, indicating that the gravitational instabilities leading to bars predominantly stem from internal processes, as suggested by recent works. Our galaxies show unexpectedly high merger fractions, possibly due to sampling bias and/or the inability of the classification method to distinguish between flybys and encounters leading to coalescence. We also find higher sSFRs for asymmetric galaxies below $M_\star\sim 10^{10.3}\,\mathrm{M}_\odot$, in agreement with the predictions for centrals from the ${\scriptsize{\rm EAGLE}}$ simulation. We release the ${\rm H}\,{\scriptsize{\rm I}}$ measurements along with ancillary galaxy and halo properties for public use.

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arXiv2026

Empirical estimates of how massive galaxies can be in {\Lambda}CDM

Using Extreme Value Statistics applied to the observed galaxy stellar mass and the UV luminosity functions, we empirically estimate masses and luminosities of the most extreme galaxies in cosmological surveys, including the full sky. We incorporate uncertainties in stellar mass measurements (Eddington bias) and the scatter in the stellar-halo mass relation to derive empirical limits for galaxies residing in the most massive halos. The maximum observed $M_\ast$ strongly depends on survey area and redshift, ranging from $M_\ast \sim 7 \times 10^{12} M_\odot$ for full-sky surveys at $z\sim0$ to $M_\ast \sim 10^{10}M_\odot$ at $z\sim16$. Massive galaxies, particularly at high redshift, approach the theoretical maximum baryonic mass available in halos $M_\ast \sim 0.16 \times M_{\mathrm{vir}}$, consistent with previous claims. Accounting for measurement uncertainties significantly reduces the inferred maximum $M_\ast$ by up to $\sim1$ dex at $z\gtrsim10$, yielding stellar masses consistent with $M_\ast < 0.16$ at all redshifts. Assuming a perfect rank-order correspondence between the most massive halos and galaxies would guarantee this inequality at all redshifts. At 2 $\lesssim$ z $\lesssim$ 6, the most massive galaxies have stellar masses comparable to the total cold gas reservoir from cold and cooling flows, suggesting near-maximal star formation efficiencies, SFEs. At higher redshifts, halos are predicted to host galaxies undergoing starburst phases. When accounting for dust attenuation and adopting empirically inferred SFEs, we find good agreement between the model and the brightest observed UV galaxies at high redshifts. At lower redshifts, however, observed UV galaxies are too bright. Overall, our results indicate that current observations remain broadly consistent with $\Lambda$CDM once statistical and observational effects are properly accounted for.

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arXiv2025

Inferring the dark matter distribution of massive galaxy clusters from deep optical observations: insights from the TNG300 simulation

Extragalactic stars within galaxy clusters contribute to the intracluster light (ICL), which is thought to be a promising tracer of the underlying dark matter (DM) distribution. In this study, we employ the TNG300 simulation to investigate the prospect of recovering the dark matter distribution of galaxy clusters from deep, wide-field optical images. For this, we generate mock observations of 40 massive clusters ($M_{200}\gtrsim 10^{14.5}\,{\rm M}_\odot$) at $z=0.06$ for the $g'$ band of the Wendelstein Wide-Field Imager (WWFI), and isolate the emission from the brightest cluster galaxy (BCG) and the ICL by masking the satellite galaxies, following observational procedures. By comparing $\Sigma_{\rm BCG+ICL}$ profiles from these images against $\Sigma_{\rm DM}$ profiles for the central subhaloes, we find that $\Sigma_{\rm cen-DM}/\Sigma_{\rm BCG+ICL}$ exhibits a quasi-linear scaling relation in log space with the normalised distance $r/R_{\Delta}$, for both $R_{\Delta}=R_{200}$ and $R_{500}$. The scatter in the scaling is predominantly stochastic, showing a weak dependence on formation time and dynamical state. We recover the DM concentration and mass within $\approx 23$ and $\approx 15$ per cent of their true values (for $R_{200}$), respectively, and with $\approx 3$ per cent larger uncertainties for $R_{500}$. Alternatively, we find that the concentration can be estimated using the BCG+ICL fraction, the central's DM mass using the BCG+ICL flux, and the total DM mass using the bolometric flux. These results demonstrate the feasibility of deriving dark matter characteristics of galaxy clusters to be observed with facilities like the Vera C. Rubin Observatory in the near future.

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arXiv2025

Photometric analysis of the intracluster light in the TNG300 simulation and wide-field observations

We present a robust, apples-to-apples comparison between the photometric properties of the intracluster light (ICL) in the TNG300 magnetohydrodynamic cosmological simulation and those in Wendelstein Wide Field Imager (WWFI) observations. This is accomplished by generating synthetic $g'$-band images of 40 massive ($\log\left(M_{\rm 200, crit}/{\rm M}_{\odot}\right) > 14.5$) TNG300 clusters at $z \approx 0.06$, closely mimicking WWFI observations, and then performing identical photometric calculations on the synthetic and real images. Importantly, we apply the same observationally motivated satellite-masking procedure to both data-sets, which effectively removes any possible biases introduced by the halo finder. We first analyze the light distribution of the `smooth' stellar component of each cluster, composed of the brightest cluster galaxy (BCG) plus the ICL, and find that it tends to be about twice as extended in TNG300 than in observations, while also being approximately 1 $g'$ mag arcsec$^{-2}$ brighter. We then quantify $f_{\rm ICL}$, the ICL fraction relative to the BCG+ICL, by considering several ICL definitions: (i) the light dimmer than a surface brightness cut at 27 $g'$ mag arcsec$^{-2}$, (ii) the excess light over a de Vaucouleurs profile, (iii) the light beyond twice the half-light radius ($2 r_{\rm half}$), and (iv) the light beyond a fixed circular aperture of 30, 50, or 100 kpc. For most definitions, the median $f_{\rm ICL}$ is consistent between simulation and observations. However, the observations exhibit larger scatter in $f_{\rm ICL}$, which we attribute primarily to observational uncertainties in the total BCG+ICL luminosity rather than `true' cluster-to-cluster variation in the real Universe. We also find that most methods yield median $f_{\rm ICL}$ values near 0.3, which is consistent with a BCG/ICL transition radius around $2 r_{\rm half}$.

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arXiv2025

The stellar mass composition of galaxy clusters and dependencies on dark matter halo properties

We analyze 700 clusters from the TNG300 hydrodynamical simulation ($M_{200}\geq5\times10^{13} \,M_{\odot}$ at (z=0)) to examine the radial stellar mass distribution of their central objects, consisting of the brightest cluster galaxy (BCG) and the intracluster light (ICL). The BCG+ICL mass fraction weakly anticorrelates with $M_{200}$, but strongly correlates with the concentration, $c_{200}$, the assembly redshift, $z_{50}$, and the mass gap between the most massive and the fourth more massive member, $\Delta M_{\rm \ast, 4th}$. We explore different aperture radii to nominally separate the ICL from the BCG and calculate ICL fractions. For $r_{\rm{ap}}=2r_{\rm half}$, where $r_{\rm half}$ is the radius containing half the BCG+ICL mass, the ICL fraction is nearly independent of $M_{200}$, $c_{200}$, and $z_{50}$ with values $M_{\ast,\rm ICL}/(M_{\ast,\rm ICL}+M_{\ast,\rm BCG})= 0.33\pm0.03$. Including the stellar mass of the satellites, the fraction $M_{\ast,\rm ICL}/(M_{\ast,\rm ICL}+M_{\ast,\rm BCG}+M_{\rm \ast,sat})$ weakly anticorrelates with $M_{200}$ and strongly correlates with $c_{200}$, $z_{50}$, and $\Delta M_{\rm \ast, 4th}$, suggesting that in more concentrated/earlier assembled/more relaxed clusters more stellar mass is lost from the satellites (by tidal stripping, and mergers) in favour of the ICL and BCG. Indeed, we find that ex-situ stars dominate both in the BCG and ICL masses, with mergers contributing more to the BCG, while tidal stripping contributes more to the ICL. We find that the difference between the projected and 3D ICL fractions are only a few per cent and suggest using $2r_{\rm half}$ to separate the ICL from the BCG in observed clusters.

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arXiv2024

Emergence of red, star-forming galaxies (red misfits) in a {\Lambda}CDM universe

We investigate the formation of red misfits (RM) using a cosmological, hydrodynamical simulation from the $\rm \small EAGLE$ project. Similar to observations, the RM possess less dust, higher stellar metallicities, and older stellar populations compared to blue, star-forming galaxies (BA) at the same $M_\star$. Lagrangian particle-tracking reveals that the older ages of RM have resulted from a combined effect of higher star formation efficiency (SFE), and the earlier onset and faster net depletion of their interstellar medium (ISM). For the centrals, the latter was partially due to higher efficiency of escape from ISM, driven by stronger stellar and/or AGN feedback (depending on the mass). There was an additional contribution to this escape from gas stripping for satellite RM, as suggested by the higher group masses ($\gtrsim 0.5$ dex) and ${\rm H_2}/{\rm H\,{\small I}}$ ratios ($\gtrsim 0.3$ dex). Moreover, accretion of circumgalactic gas (CGM) onto the galaxy has been less efficient for the satellites. On the metallicity front, the offsets are largely due to the disparity in SFE, causing varying degrees of enrichment through the mass-transfers associated with stellar winds and supernovae. We ascribe this SFE disparity to the lower specific angular momentum ($j$) of freshly accreted CGM for RM, which ultimately manifested in the ISM kinematics due to interactions with cooling flows. The impact on $j_{\rm ism}$ was further intensified by poorer alignment with the flow's $\vec{j}$, particularly for the satellites. Our results illuminate potential origins of RM, and motivate further exploration of this peculiar class through a synergy between observations and simulations.

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arXiv2022

The relationship between cluster environment and molecular gas content of star-forming galaxies in the EAGLE simulation

We employ the EAGLE hydrodynamical simulation to uncover the relationship between cluster environment and $\rm H_2$ content of star-forming galaxies at redshifts spanning $0\leq z\leq 1$. To do so, we divide the star-forming sample into those that are bound to clusters and those that are not. We find that, at any given redshift, the galaxies in clusters generally have less $\rm H_2$ than their non-cluster counterparts with the same stellar mass (corresponding to an offset of $\lesssim 0.5$ dex), but this offset varies with stellar mass and is virtually absent at $M_\star\lesssim10^{9.3}~{\rm M}_\odot$. The $\rm H_2$ deficit in star-forming cluster galaxies can be traced back to a decline in their $\rm H_2$ content that commenced after first infall into a cluster, which occurred later than a typical cluster galaxy. Evolution of the full cluster population after infall is generally consistent with `slow-then-rapid' quenching, but galaxies with $M_\star\lesssim 10^{9.5}~{\rm M}_\odot$ exhibit rapid quenching. Unlike most cluster galaxies, star-forming ones were not pre-processed in groups prior to being accreted by clusters. For both of these cluster samples, the star formation efficiency remained oblivious to the infall. We track the particles associated with star-forming cluster galaxies and attribute the drop in $\rm H_2$ mass after infall to poor replenishment, depletion due to star formation, and stripping of $\rm H_2$ in cluster environments. These results provide predictions for future surveys, along with support and theoretical insights for existing molecular gas observations that suggest there is less $\rm H_2$ in cluster galaxies.

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arXiv2021

Drivers of asymmetry in synthetic H I emission-line profiles of galaxies in the EAGLE simulation

We study the shapes of spatially integrated H I emission-line profiles of galaxies in the EAGLE simulation using three separate measures of the profile's asymmetry. We show that the subset of EAGLE galaxies whose gas fractions and stellar masses are consistent with those in the xGASS survey also have similar H I line asymmetries. Central galaxies with symmetric H I line profiles typically correspond to rotationally supported H I and stellar disks, but those with asymmetric line profiles may or may not correspond to dispersion-dominated systems. Galaxies with symmetric H I emission lines are, on average, more gas rich than those with asymmetric lines, and also exhibit systematic differences in their specific star formation rates, suggesting that turbulence generated by stellar or AGN feedback may be one factor contributing to H I line asymmetry. The line asymmetry also correlates strongly with the dynamical state of a galaxy's host dark matter halo: older, more relaxed haloes host more-symmetric galaxies than those hosted by unrelaxed ones. At fixed halo mass, asymmetric centrals tend to be surrounded by a larger number of massive subhaloes than their symmetric counterparts, and also experience higher rates of gas accretion and outflow. At fixed stellar mass, central galaxies have, on average, more symmetric H I emission lines than satellites; for the latter, ram pressure and tidal stripping are significant sources of asymmetry.

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arXiv2021

The COS-legacy survey of C IV absorbers: properties and origins of the intervening systems

We present here results from a survey of intervening C IV absorbers at $z < 0.16$ conducted using 223 sightlines from the Hubble Spectroscopic Legacy Archive. Most systems (83%) out of the total sample of 69 have simple kinematics with 1 or 2 C IV components. In the 22 C IV systems with well constrained H I column densities, the temperatures from the $b$-values imply predominantly photoionized plasma ($T\leq 10^5$ K) and non-thermal dynamics. These systems also have solar or higher metallicities. We obtain a C IV line density of $d\mathcal{N}/dX = 5.1\pm 1.0$ for $\log [N(C~IV)~(cm^{-2})]\geq12.9$, and $Ω_{C~IV}=(8.01\pm 1.62) \times 10^{-8}$ for $12.9 \leq \log [N(C~IV)~(cm^{-2})] \leq 15.0$. The C IV bearing diffuse gas in the $z < 0.16$ Universe has a metallicity of $(2.07~{\pm}~0.43)~\times~10^{-3}$ Z$_{\odot}$, an order of magnitude more than the metal abundances in the IGM at high redshifts ($z \gtrsim 5$), and consistent with the slow build-up of metals in the diffuse circum/intergalactic space with cosmic time. For $z<0.015$ (complete above $L>0.01L^\star$), the Sloan Digital Sky Survey provides a tentative evidence of declining covering fraction for strong C IV ($N>10^{13.5}~cm^{-2}$) with $ρ$ (impact parameter) and $ρ/R_\mathrm{vir}$. However, the increase at high separations suggests that strong systems are not necessarily coincident with such galaxies. We also find that strong C IV absorption at $z<0.051$ is not coincident with galaxy over-dense regions complete for $L>0.13L^\star$

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arXiv2019

C IV absorbers tracing cool gas in dense galaxy group/cluster environments

We present analysis on three intervening H I-C IV absorption systems tracing gas within galaxy group/cluster environments, identified in the $HST$/COS far-UV spectra of the background quasars PG $1148+549$ ($z_{abs}=0.00346$), SBS~$1122+594$ ($z_{abs}=0.00402$) and RXJ~$1230.8+0115$ ($z_{abs}=0.00574$). The ionization models are consistent with the origin of metal lines and H I from a cool and diffuse photoionized gas phase with $T \lesssim 4 \times 10^{4}$ K and $n_{\mathrm{H}} \lesssim 5 \times 10^{-4}$ cm$^{-3}$. The three absorbers have $89$, $51$ and $17$ galaxies detected within $1$ Mpc and $|Δv| < 600$ km s$^{-1}$. The RXJ~$1230.8+0115$ sightline traces the outskirt regions of the Virgo cluster where the absorber is found to have super-solar metallicity. The detection of metal lines along with H I has enabled us to confirm the presence of cool, diffuse gas possibly enriched by outflows and tidal interactions in environments with significant galaxy density.

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