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Saloni Agrawal

Publications and source records attributed to Saloni Agrawal.

5 recordsLinked to original sources
arXiv2026

KCWI Observations of Type 2 Quasar-driven Ionized Outflows at z~0.1

AGN-driven outflows play a crucial role in regulating star formation in galaxies. These outflows are known to be multi-phase, and the characterization of the kinematics, extent, and energetics of each gas phase is needed to obtain a full picture of the outflow properties and impact. This study presents Keck Cosmic Web Imager (KCWI) integral field spectroscopy of the ionized gas outflow properties in seven low redshift (z<0.1) quasars---six Type 2 AGN and one narrow-line Type 1 AGN---providing insight into the warm ionized outflows in these luminous AGN. With the large field-of-view and high sensitivity of KCWI, these data reveal both larger ionized outflow extents than were previously known for these sources and uncover the existence of additional high-velocity kinematic components in the ionized outflows of these luminous AGN. We find (a) a high incidence (50-70%) of multiple outflows on scales of 4--10 kpc and (b) trends between the outflow extent, kinematics, and the ionized mass and energy outflow rates. These trends imply that the faster and often smaller outflows carry higher mass and energy outflow rates than the slower, larger outflows. We also find that the ionized gas outflows reach as far as the known extent of narrow-line ionized gas emission in AGN, which is known to depend weakly on AGN luminosity. This work highlights the utility of the current generation of wide-field integral field spectrographs on 8--10m class telescopes for studying quasar-driven outflows.

astro-ph.GA↗
arXiv2026

Red vs. Blue: How metallicity shapes black hole dynamics and mergers in dense star clusters

Dense star clusters are a well-established environment for the formation of gravitational wave sources through dynamical interactions. Recent LIGO-Virgo-KAGRA (LVK) events such as GW241011 and GW241110 provide some of the best evidence yet for a dynamical origin. However, their relatively low component masses are in tension with predictions from low-metallicity globular cluster models (which typically produce more massive black holes), hinting that these events may have originated in higher-metallicity environments. Here we present a new set of Monte Carlo star cluster simulations with refined coverage in metallicity, focusing specifically on clusters with [Fe/H] $\geq-1$, similar to the ''red'' globular cluster subpopulation observed in most galaxies. We show that metallicity has a significant effect on the mass function of black holes and black hole mergers, the total number of black hole mergers per cluster, black hole retention from natal kicks, the mass segregation time for black-hole-driven cluster dynamics, and the merger delay time distribution. We also show that high-metallicity cluster models produce low-mass hierarchical mergers consistent with the mass ratios and component masses of GW241011 and GW241110, motivating the importance of high-metallicity clusters in the astrophysical interpretation of future LVK catalogs.

astro-ph.GA↗
arXiv2026

Black hole mergers from dense star clusters with realistic binary populations

We present a suite of 24 full-lifetime simulations of dense star clusters with the Cluster Monte Carlo (CMC) code, featuring updated input physics and a realistic distribution of initial binary systems. The latter encompasses a mass-dependent binary fraction, period distribution, and eccentricity distribution based on observations of well-studied stellar populations in the Solar neighborhood and nearby star-forming regions. We predict the cosmic rate, masses, and spins of binary black hole (BBH) mergers formed through dynamical assembly, primordial binary evolution, and hierarchical mergers within dense clusters. As with previous model grids with fewer binaries, dynamically assembled first-generation (1G) mergers dominate the rate of cluster-derived mergers, and the total merger rate is consistent with that inferred from LIGO-Virgo-KAGRA observations as of GWTC-5.0. Our models naturally reproduce key features of the inferred BBH population, including the broken-power-law behavior of the primary BH mass spectrum for $m_1 \gtrsim 20 M_\odot$, the shallower (steeper) slope of the secondary mass spectrum relative to the primary for $m_2 \lesssim 10 M_\odot$ ($m_2 \gtrsim 30 M_\odot$), and the shape of the mass-ratio distribution in the low- and high-mass domains. We predict broad distributions of the spin parameters $χ_{\mathrm{eff}}$ and $χ_{\mathrm{p}}$, consistent with previous studies of dynamical assembly in clusters. The merger rate from primordial binary systems within clusters is a small fraction of the total; however, their merger products are frequently involved in subsequent hierarchical mergers, with the result that the hierarchical merger rate evolves more steeply than the 1G dynamical merger rate with redshift.

astro-ph.GA↗
arXiv2026

A Shocked Wind Interpretation of an Odd Radio Circle

Odd Radio Circles (ORCs) are a new class of extragalactic object, with large rings of faint radio continuum emission typically spanning 100s of kpc; their origins are unknown. Previous optical spectroscopy of the central galaxy in ORC4, a classic isolated ORC, revealed spatially-extended ionized gas with strong [OII] emission and line ratios consistent with LINER emission. We present new Keck/KCWI+KCRM integral field spectroscopy covering multiple strong optical emission lines to measure the extent, morphology, and spatially-resolved kinematics and line ratios of the ionized and neutral gas in the ORC4 central galaxy. We find that [OII] is the strongest optical emission line in this massive, old galaxy, and the [OII] emission is detected to larger radial extent than the other optical lines. The gas kinematics show strong spatial asymmetries, high velocity gradients (>100 km/s), and high velocity dispersion (~200 km/s). The emission line ratios are most consistent with shock models with shock velocities of ~200-300 km/s and are not fit well by stellar or AGN photoionization models. These findings are consistent with a model in which the gas in the ORC4 central galaxy is the result of shock ionization in and around the central galaxy, likely due to mixing and cooling of gas associated with the event that created the large-scale radio ring of emission that identified this source as an ORC.

astro-ph.GA↗