Browsing by Author "Evans, Aaron"

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    Molecular Gas in Major Mergers Hosting Dual and Single AGNs at
    (2025) Johnstone, Makoto A.; Treister, Ezequiel; Bauer, Franz E.; Chin-Shin Chang; Cicone, Claudia; Koss, Michael J.; Del Moral Castro, Ignacio; Muller Sanchez, Francisco; Privon, George C.; Ricci, Claudio; Scoville, Nick; Venturi, Giacomo; Barcos Muñoz, Loreto; Armus, Lee; Blecha, Laura; Casey, Caitlin; Comerford, Julia; Evans, Aaron; Kawamuro, Taiki; Medling, Anne M.; Messias, Hugo; Nagar, Neil; Rojas, Alejandra; Sanders, David; Trakhtenbrot, Benny; U, Vivian; Urry, Meg
    We present high-resolution (∼50–100 pc) Atacama Large Millimeter/submillimeter Array observations of 12CO(2–1) or 12CO(1–0) emission in seven local (z ≲ 0.05) major mergers—five of which are dual active galactic nucleus (AGN) systems, and two of which are single AGN systems. We model the molecular gas kinematics through rotating disk profiles using a Bayesian Markov Chain Monte Carlo approach. The residuals were then used to isolate nonrotating components of the molecular gas—the most likely contributor to future supermassive black hole (SMBH) growth. We find that more-massive SMBHs have higher surface densities of nonrotating molecular gas within their sphere of influence. This potential molecular gas supply, however, does not correlate with the current accretion efficiency of the SMBHs, suggesting that only a fraction of the observed nonrotating gas is currently reaching the SMBH. Finally, we tentatively find no significant differences in the nuclear molecular gas masses of single-AGN and dual-AGN hosts, both within the SMBH sphere of influence and within the central kiloparsec. Our results indicate that the probability of occurrence of the dual AGN phenomenon is likely dependent on AGN variability and/or obscuration rather than the availability of molecular gas in the nuclear regions.
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    The Arp 240 Galaxy Merger: A Detailed Look at the Molecular Kennicutt-Schmidt Star Formation Law on Subkiloparsec Scales
    (IOP Publishing Ltd, 2025) Saravia, Alejandro; Rodas Quito, Eduardo; Barcos Muñoz, Loreto; Evans, Aaron; Kunneriath, Devaky; Privon, George; Song, Yiqing; Yoon, Ilsang; Emig, Kimberly L.; Sánchez Garcia, María; Linden, Sean; Green, Kara Noelle; Johnstone, Makoto; Nagarajan Swenson, Jaya; Meza, Gabriela A.; Momjian, Emmanuel; Armus, Lee; Charmandaris, Vassilis; Díaz Santos, Tanio; Treister, Ezequiel
    The molecular Kennicutt-Schmidt Law has been key for understanding star formation (SF) in galaxies across allredshifts. However, recent subkiloparsec observations of nearby galaxies reveal deviations from the nearly unityslop e(N) obtained with disk-averaged measurements. We study SF and molecular gas (MG) distribution in theearly-stage luminous infrared galaxy merger Arp 240(NGC 5257-8). Using Very Large Array radio continuum (RC) and Atacama Large Millimeter/submillimeter Array CO(2-1)observations at 500 pc scale, with a uniformgrid analysis, we estimate SF rates and MG surface densities (Sigma(SFR) and H-2, respectively). In Arp 240,Nissublinear at 0.52 +/- 0.17. For NGC 5257 and NGC 5258,Nis 0.52 +/- 0.16 and 0.75 +/- 0.15, respectively. Weidentify two SF regimes: high surface brightness (HSB) regions in RC with N similar to 1, and low surface brightness (LSB) regions with shallow N (ranging 0.15 +/- 0.09-0.48 +/- 0.04). Median CO(2-1) linewidth and MG turbulent pressure (P-turb) are 25 km s(-1) and 9 x 10(5) K cm(-3). No significant correlation was found between Sigma(SFR) and CO(2-1) linewidth. However, Sigma(SFR) correlates with P-turb, particularly in HSB regions (rho>0.60). In contrast, SF efficiency moderately anticorrelates with P-turb in LSB regions but shows no correlation in HSB regions. Additionally, we identify regions where peaks in SF and MG are decoupled, yielding a shallow N (<= 0.28 +/- 0.18). Overall, the range of N reflects distinct physical properties and distribution of both the SF and MG, which can be masked by disk-averaged measurements.