Browsing by Author "Molina, Juan "

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    Compact Molecular Gas Distribution in Quasar Host Galaxies
    (2021) Molina, Juan ; Wang, Ran ; Shangguan, Jinyi ; Ho, Luis C. ; Bauer, Franz E. ; Treister, Ezequiel ; Shao, Yali
    We use Atacama Large Millimeter/submillimeter Array CO (2-1) observations of six low-redshift Palomar-Green quasars to study the distribution and kinematics of the molecular gas of their host galaxies at kiloparsec-scale resolution. While the molecular gas content, molecular gas fraction, and star formation rates are similar to those of nearby massive, star-forming galaxies, the quasar host galaxies possess exceptionally compact, disky molecular gas distributions with a median half-light radius of 1.8 kpc and molecular gas mass surface densities greater than or similar to 22 M pc(-2). While the overall velocity field of the molecular gas is dominated by regular rotation out to large radii, with ratio of rotation velocity to velocity dispersion greater than or similar to 9, the nuclear region displays substantial kinematic complexity associated with small-scale substructure in the gas distribution. A tilted-ring analysis reveals that the kinematic and photometric position angles are misaligned on average by similar to 34 degrees 26 degrees and provides evidence of kinematic twisting. These observations provide tantalizing clues to the detailed physical conditions of the circumnuclear environments of actively accreting supermassive black holes.
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    Constraining Quasar Feedback from Analysis of the Hydrostatic Equilibrium of the Molecular Gas in Their Host Galaxies
    (Institute of Physics, 2024) Fei, Qinyue; Wang, Ran; Molina, Juan; Ho, Luis C.; Shangguan, Jinyi; Bauer, Franz Erik; Treister, Ezequiel
    We investigate the kinematics and dynamics of the molecular and ionized gas in the host galaxies of three Palomar-Green quasars at low redshifts, benefiting from the archival millimeter-wave interferometric and optical integral field unit data. We study the kinematics of both cold molecular and hot ionized gas by analyzing the CO and Hα data cubes, and construct the mass distributions of our sample through gas dynamics, utilizing a priori knowledge regarding the galaxy light distribution. We find no systematic offset between the stellar mass derived from our dynamical method and that from the broadband photometry and mass-to-light ratio, suggesting the consistency of both methods. We then study the kinetic pressure and the weight of the interstellar medium (ISM) using our dynamical mass model. By studying the relationship between kinetic pressure and gravitational pressure of the quasar host galaxies, we find an equivalence in the hydrostatic equilibrium states of ISM in the quasar host galaxies, similar to the result of gas equilibrium in normal star-forming galaxies, suggesting minimal quasar feedback. Regarding noncircular motion as indicative of quasar-driven outflows, we observe an exceptionally low coupling efficiency between molecular gas outflow and active galactic nucleus bolometric luminosities. These results demonstrate the marginal influence of the central engine on the properties of cold molecular gas in quasar host galaxies.
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    Dynamics of Molecular Gas in the Central Region of the Quasar I Zwicky 1
    (2023) Fei, Qinyue; Wang, Ran; Molina, Juan; Shangguan, Jinyi; Ho, Luis C.; Bauer, Franz E.; Treister, Ezequiel
    We present a study of the molecular gas distribution and kinematics in the cicumnuclear region (radii less than or similar to 2 kpc) of the z approximate to 0.061 quasar I Zwicky 1 using a collection of available Atacama Large Millimeter/submillimeter Array observations of the carbon monoxide (CO) emission. With an angular resolution of similar to 0.'' 36 (corresponding to similar to 400 pc), the host-galaxy substructures including the nuclear molecular gas disk, spiral arms, and a compact bar-like component are resolved. We analyzed the gas kinematics based on the CO image cube and obtained the rotation curve and radial distribution of velocity dispersion. The velocity dispersion is about 30 km s(-1) in the outer CO disk region and rises up to greater than or similar to 100 km s(-1) at radius less than or similar to 1 kpc, suggesting that the central region of the disk is dynamically hot. We constrain the CO-to-H-2 conversion factor, alpha(CO), by modeling the cold gas disk dynamics. We find that, with prior knowledge about the stellar and dark matter components, the alpha(CO) value in the circumnuclear region of this quasar host galaxy is 1.55(-0.49)(+0.47) M-circle dot (K km s(-1) pc(2))(-1), which is between the value reported in ultraluminous infrared galaxies and in the Milky Way. The central 1 kpc region of this quasar host galaxy has significant star formation activity, which can be identified as a nuclear starburst. We further investigate the high-velocity dispersion in the central region. We find that the interstellar medium (ISM) turbulent pressure derived from the gas velocity dispersion is in equilibrium with the weight of the ISM. This argues against extra power from active galactic nuclei feedback that significantly affects the kinematics of the cold molecular gas.
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    Enhanced Star Formation Efficiency in the Central Regions of Nearby Quasar Hosts
    (2023) Molina, Juan; Ho, Luis C.; Wang, Ran; Shangguan, Jinyi; Bauer, Franz E.; Treister, Ezequiel
    We combine Atacama Large Millimeter/submillimeter Array and Multi Unit Spectroscopic Explorer observations tracing the molecular gas, millimeter continuum, and ionized gas emission in six low-redshift (z less than or similar to 0.06) Palomar-Green (PG) quasar host galaxies to investigate their ongoing star formation at roughly kiloparsec-scale resolution. The AGN contribution to the cold dust emission and the optical emission-line flux is carefully removed to derive spatial distributions of the star formation rate (SFR), which, complemented with the molecular gas data, enables the mapping of the depletion time (t (dep)). We report ubiquitous star formation activity within the quasar host galaxies, with the majority of the ongoing star formation occurring in the galactic center. The rise of the SFR surface density (sigma(SFR)) toward the nucleus is steeper than that observed for the cold molecular gas surface density, reaching values up to sigma(SFR) approximate to 0.15-0.80 M (circle dot) yr(-1) kpc(-2). The gas in the nuclear regions is converted into stars at a shortened depletion time (t (dep) approximate to 0.2-2.0 Gyr), suggesting that those zones can be deemed as starbursts. At large galactocentric radius, we find that the ongoing star formation takes place within spiral arms or H ii region complexes, with an efficiency comparable to that reported for nearby inactive spirals (t (dep) approximate to 1.8 Gyr). We find no evidence of star formation activity shutoff in the PG quasar host galaxies. On the contrary, these observations shed light on how the central environments of galaxies hosting actively accreting supermassive black holes build up stellar mass.
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    Ionized Outflows in Nearby Quasars Are Poorly Coupled to Their Host Galaxies
    (2022) Molina, Juan; Ho, Luis C.; Wang, Ran; Shangguan, Jinyi; Bauer, Franz E.; Treister, Ezequiel; Zhuang, Ming-Yang; Ricci, Claudio; Bian, Fuyan
    We analyze Multi-Unit Spectroscopic Explorer observations of nine low-redshift (z < 0.1) Palomar-Green quasar host galaxies to investigate the spatial distribution and kinematics of the warm, ionized interstellar medium, with the goal of searching for and constraining the efficiency of active galactic nucleus (AGN) feedback. After separating the bright AGN from the starlight and nebular emission, we use pixel-wise, kpc-scale diagnostics to determine the underlying excitation mechanism of the line emission, and we measure the kinematics of the narrow-line region (NLR) to estimate the physical properties of the ionized outflows. The radial size of the NLR correlates with the AGN luminosity, reaching scales of similar to 5 kpc and beyond. The geometry of the NLR is well-represented by a projected biconical structure, suggesting that the AGN radiation preferably escapes through the ionization cone. We find enhanced velocity dispersions (greater than or similar to 100 km s(-1)) traced by the H alpha emission line in localized zones within the ionization cones. Interpreting these kinematic features as signatures of interaction between an AGN-driven ionized gas outflow and the host galaxy interstellar medium, we derive mass-outflow rates of similar to 0.008-1.6 M (circle dot) yr(-1) and kinetic injection rates of similar to 10(39)-10(42) erg s(-1), which yield extremely low coupling efficiencies of less than or similar to 10(-3). These findings add to the growing body of recent observational evidence that AGN feedback is highly ineffective in the host galaxies of nearby AGNs.
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    Lack of Correlations between Cold Molecular Gas and AGN Properties in Type 1 AGNs at z ≲ 0.5
    (2023) Molina, Juan; Shangguan, Jinyi; Wang, Ran; Ho, Luis C.; Bauer, Franz Erik; Treister, Ezequiel
    We present new NOrthern Extended Millimeter Array (NOEMA) observations of the CO(2–1) emission in eight of the brightest Palomar-Green quasars at z ≲ 0.5 to investigate the role of active galactic nucleus (AGN) feedback in luminous quasars detected at low redshifts. We detect CO(2–1) emission in three objects, from which we derive CO luminosities, molecular gas masses and fractions, and gas depletion times. In combination with data available in the literature, we build a total sample of 138 local type 1 AGNs with CO(2–1) measurements. We compare the AGN properties with the host galaxy molecular gas properties, considering systems nondetected in CO emission. We find that the CO luminosity does not correlate with AGN luminosity and Eddington ratio, while the molecular gas fraction is weakly correlated with Eddington ratio. The type 1 AGNs can be roughly separated into two populations in terms of infrared-to-CO luminosity ratio, with one population presenting values typically found in normal star-forming systems, while the other having lower ratio values, comparable to those measured for starbursts. We find no evidence that AGN feedback rapidly quenches star formation in type 1 AGNs. Our results may imply an underlying the role of host galaxy gravitational instabilities or the fast inflow of cold gas in triggering AGN activity.