Dense Molecular Gas Properties of the Central Kpc of Nearby Ultraluminous Infrared Galaxies Constrained by ALMA Three Transition-line Observations

Abstract

We report the results of ALMA 1-2 kpc-resolution, three rotational transition line (J=2-1, J=3-2, and J=4-3) observations of multiple dense molecular gas tracers (HCN, HCO${}^{+}$, and HNC) for ten nearby (ultra)luminous infrared galaxies ([U]LIRGs). Following the matching of beam sizes to 1-2 kpc for each (U)LIRG, the high-J to low-J transition-line flux ratios of each molecule and the emission line flux ratios of different molecules at each J transition are derived. We conduct RADEX non-LTE model calculations and find that, under a wide range of gas density and kinetic temperature, the observed HCN-to-HCO${}^{+}$ flux ratios in the overall (U)LIRGs are naturally reproduced with enhanced HCN abundance compared to HCO${}^{+}$. Thereafter, molecular gas properties are constrained primarily through the use of HCN and HCO${}^{+}$ data and the adoption of fiducial values for the HCO${}^{+}$ column density and HCN-to-HCO${}^{+}$ abundance ratio. We quantitatively confirm the following: (1) Molecular gas at the (U)LIRGs' nuclei is dense ($\gtrsim$10${}^{3-4}$ cm${}^{-3}$) and warm ($\gtrsim$100 K). (2) Molecular gas density and temperature in nine ULIRGs' nuclei are significantly higher than that of one LIRG's nucleus. (3) Molecular gas in starburst-dominated sources tends to be less dense and cooler than ULIRGs with luminous AGN signatures. For six selected sources, we also apply a Bayesian approach by freeing all parameters and support the above main results. Our ALMA 1-2 kpc resolution, multiple transition-line data of multiple molecules are a very powerful tool for scrutinizing the properties of molecular gas concentrated around luminous energy sources in nearby (U)LIRGs' nuclei.

42 pages, 13 figures. ApJ accepted

References in corpus (40)

• Array Programming with NumPy
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• CASA, the Common Astronomy Software Applications for Radio Astronomy
• The Critical Density and the Effective Excitation Density of Commonly Observed Molecular Dense Gas Tracers
• Diagnostics of irradiated dense gas in galaxy nuclei. II. A grid of XDR and PDR models
• A multi-transition HCN and HCO+ study of 12 nearby active galaxies: AGN versus SB environments
• A 2 mm spectral line survey of the starburst galaxy NGC 253
• Molecular gas in extreme star-forming environments: the starbursts Arp220 and NGC6240 as case studies
• The Herschel Comprehensive (U)LIRG Emission Survey (HerCULES): CO Ladders, fine structure lines, and neutral gas cooling
• A Spitzer IRS Low-Resolution Spectroscopic Search for Buried AGNs in Nearby Ultraluminous Infrared Galaxies - A Constraint on Geometry between Energy Sources and Dust -
• Molecular line emission in NGC1068 imaged with ALMA: II. The chemistry of the dense molecular gas
• Interacting galaxies on FIRE-2: The connection between enhanced star formation and interstellar gas content
• High resolution observations of HCN and HCO+ J=3-2 in the disk and outflow of Mrk231 -Detection of vibrationally excited HCN in the warped nucleus
• ALMA Imaging of HCN, CS and dust in Arp 220 and NGC 6240
• The HNC/HCN Ratio in Star-Forming Regions
• Low-J CO Line Ratios From Single Dish CO Mapping Surveys and PHANGS-ALMA
• Lambda = 3 mm line survey of nearby active galaxies
• Millimeter-Wave Line Ratios and Sub-beam Volume Density Distributions
• Molecular gas heating mechanisms, and star formation feedback in merger/s tarbursts: NGC 6240 and Arp 193 as case studies
• High-J CO SLEDs in nearby infrared bright galaxies observed by Herschel-PACS
• ALMA HCN and HCO+ J=3-2 observations of optical Seyfert and luminous infrared galaxies -- Confirmation of elevated HCN-to-HCO+ flux ratios in AGNs --
• On the Detection of High Redshift Black Holes with ALMA through CO and H2 Emission
• ALMA 0.02"-resolution observations reveal HCN-abundance-enhanced counter-rotating and outflowing dense molecular gas at the NGC 1068 nucleus
• HCN to HCO^+ Millimeter Line Diagnostics of AGN Molecular Torus I : Radiative Transfer Modeling
• Are local ULIRGs powered by AGN? The sub-kpc view of the 220 GHz continuum. PUMA II
• Warm molecular gas temperature distribution in six local infrared bright Seyfert galaxies
• ALMA Observations of Nearby Luminous Infrared Galaxies with Various AGN Energetic Contributions Using Dense Gas Tracers
• ALMA Spatially-resolved Dense Molecular Gas Survey of Nearby Ultraluminous Infrared Galaxies
• 3-5 micron spectroscopy of obscured AGNs in ULIRGs
• A New Radio Molecular Line Survey of Planetary Nebulae: HNC/HCN as a Diagnostic of Ultraviolet Irradiation
• An Evolutionary Paradigm for Dusty Active Galaxies at Low Redshift
• A molecular line survey toward the nearby galaxies NGC 1068, NGC 253, and IC 342 at 3 mm with the Nobeyama 45 m radio telescope: The data
• A Massive Molecular Torus inside a Gas-Poor Cirnumnuclear Disk in the Radio Galaxy NGC 1052 Discovered with ALMA
• The Near-Infrared CO Absorption Band as a Probe to the Innermost Part of an AGN Obscuring Material
• Understanding if molecular ratios can be used as diagnostics of AGN and starburst activity: The case of NGC 1068
• Central molecular zones in galaxies: multitransition survey of dense gas tracers HCN, HNC, and HCO+
• Sub-kiloparsec empirical relations and excitation conditions of HCN and HCO+ J=3-2 in nearby star-forming galaxies
• Cold Molecular Gas in Merger Remnants. II. The properties of dense molecular gas
• ALMA detection of millimetre 183 GHz H2O maser emission in the Superantennae galaxy at z ~ 0.06
• ALMA Sub-arcsec-resolution 183 GHz H2O and Dense Molecular Line Observations of Nearby Ultraluminous Infrared Galaxies

Cited by in corpus (5)

• SUNRISE: The rich molecular inventory of high-redshift dusty galaxies revealed by broadband spectral line surveys
• CON-quest II. Spatially and spectrally resolved HCN/HCO+ line ratios in local luminous and ultraluminous infrared galaxies
• A multi-scale investigation into the diagnostic potential of the HCN/HCO${}^{+}$ ratio for AGN and starburst activity in nearby galaxies
• A possible relation between global CO excitation and massive molecular outflows in local ULIRGs
• Surveying the Whirlpool at Arcseconds with NOEMA (SWAN) II: Survey design and observations