Discovery of Hydrogen Radio Recombination Lines at z=0.89 towards PKS 1830-211

Abstract

We report the detection of stimulated hydrogen radio recombination line (RRL) emission from ionized gas in a $z=0.89$ galaxy using 580--1670 MHz observations from the MeerKAT Absorption Line Survey (MALS). The RRL emission originates in a galaxy that intercepts and strongly lenses the radio blazar PKS 1830-211 ($z=2.5$). This is the second detection of RRLs outside of the local universe and the first clearly associated with hydrogen. We detect effective H144$\alpha$ (and H163$\alpha$) transitions at observed frequencies of 1156 (798) MHz by stacking 17 (27) RRLs with 21$\sigma$ (14$\sigma$) significance. The RRL emission contains two main velocity components and is coincident in velocity with HI 21 cm and OH 18 cm absorption. We use the RRL spectral line energy distribution and a Bayesian analysis to constrain the density ($n_e$) and the volume-averaged pathlength ($\ell$) of the ionized gas. We determine $\log (n_e)=2.0_{-0.7}^{+1.0}$ cm${}^{-3}$ and $\log (\ell )=-0.7_{-1.1}^{+1.1}$ pc towards the north east (NE) lensed image, likely tracing the diffuse thermal phase of the ionized ISM in a thin disk. Towards the south west (SW) lensed image, we determine $\log (n_e)=3.2_{-1.0}^{+0.4}$ cm${}^{-3}$ and $\log (\ell )=-2.7_{-0.2}^{+1.8}$ pc, tracing gas that is more reminiscent of H II regions. We estimate a star formation (surface density) rate of ${\Sigma }_{\mathrm{SFR}}\sim 0.6$ M${}_{\odot }$ yr${}^{-1}$ kpc${}^{-2}$ or SFR $\sim 50$ M${}_{\odot }$ yr${}^{-1}$, consistent with a star-forming main sequence galaxy of $M_{\star }\sim 10^{11}$ M${}_{\odot }$. The discovery presented here opens up the possibility of studying ionized gas at high redshifts using RRL observations from current and future (e.g., SKA and ngVLA) radio facilities.

arXiv comment17 pages, 10 figures, 2 tables, accepted in ApJ

References in corpus (59)

• Array Programming with NumPy
• emcee: The MCMC Hammer
• The Global Schmidt Law in Star Forming Galaxies
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Starburst99: Synthesis Models for Galaxies with Active Star Formation
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• CASA, the Common Astronomy Software Applications for Radio Astronomy
• The GMRT 150 MHz All-sky Radio Survey: First Alternative Data Release TGSS ADR1
• The Herschel view of the dominant mode of galaxy growth from z=4 to the present day
• Understanding Galaxy Evolution through Emission Lines
• Massive Dark-matter halos and Evolution of Early-type Galaxies to z=1
• On the fraction of star formation occurring in bound stellar clusters
• An uncertainty principle for star formation. I. Why galactic star formation relations break down below a certain spatial scale
• The Scale Dependence of the Molecular Gas Depletion Time in M33
• Three Dimensional Hydrodynamic Simulations of Multiphase Galactic Disks with Star Formation Feedback: I. Regulation of Star Formation Rates
• Molecules at z=0.89: A 4-mm-rest-frame absorption line survey toward PKS 1830-211
• The Time Delay in the Gravitational Lens PKS 1830-211
• Revisiting the Integrated Star Formation Law. II. Starbursts and the Combined Global Schmidt Law
• A precise and accurate determination of the cosmic microwave background temperature at z=0.89
• Pressure-Regulated, Feedback-Modulated Star Formation In Disk Galaxies
• The interstellar and circumnuclear medium of active nuclei traced by HI 21-cm absorption
• Effective Radii of Young, Massive Star Clusters in Two LEGUS Galaxies
• The Chemical Evolution of Helium
• The redshift of the gravitationally lensed radio source PKS1830-211
• The Ionized Gas in Nearby Galaxies as Traced by the [NII] 122 and 205 μm Transitions
• A strong magnetic field in the jet base of a supermassive black hole
• Metallicity Structure in the Milky Way Disk Revealed by Galactic HII Regions
• An ALMA Early Science survey of molecular absorption lines toward PKS1830-211 -- Analysis of the absorption profiles
• PKS 1830-211: A Possible Compound Gravitational Lens
• Comparing the pre-SNe feedback and environmental pressures for 6000 HII regions across 19 nearby spiral galaxies
• Drastic changes in the molecular absorption at redshift z=0.89 toward the quasar PKS 1830-211
• The kinetic temperature of a molecular cloud at redshift 0.9: Ammonia in the gravitational lens PKS1830-211
• The galaxy-wide distributions of mean electron density in the HII regions of M51 and NGC 4449
• Probing the jet base of the blazar PKS1830-211 from the chromatic variability of its lensed images. Serendipitous ALMA observations of a strong gamma-ray flare
• Illuminating the past 8 billion years of cold gas towards two gravitationally lensed quasars
• Cosmic alignment towards the radio Einstein ring PKS 1830-211 ?
• Diffuse Ionized Gas in Simulations of Multiphase, Star-Forming Galactic Disks
• Carbon and hydrogen radio recombination lines from the cold clouds towards Cassiopeia A
• Changes in the measured image separation of the gravitational lens system, PKS 1830-211
• The First Large Absorption Survey in HI (FLASH): I. Science Goals and Survey Design
• Blind HI and OH absorption line search: first results with MALS and uGMRT processed using ARTIP
• Interstellar Broadening of Images in the Gravitational Lens PKS 1830-211
• Image Deconvolution of the Radio Ring PKS 1830-211
• Low Frequency Carbon Radio Recombination Lines I: Calculations of Departure Coefficients
• New molecular species at redshift z=0.89
• LOFAR observations of decameter carbon radio recombination lines towards Cassiopeia A
• A study of submillimeter methanol absorption toward PKS1830-211: Excitation, invariance of the proton-electron mass ratio, and systematics
• PKS1830-211: OH and HI at z=0.89 and the first MeerKAT UHF spectrum
• Low Frequency Carbon Radio Recombination Lines II: The Diffuse Interstellar Medium
• Correlation between SFR surface density and thermal pressure of ionized gas in local analogs of high-redshift galaxies
• All good things come in threes: the third image of the lensed quasar PKS1830-211
• The first detection of radio recombination lines at cosmological distances
• Filamentary structures of ionized gas in Cygnus X
• The inhomogeneous ISM toward PKS1830-211 SW - A detailed view on molecular gas at a look-back time of 7.5 Gyr
• Submillimeter polarization and variability of quasar PKS 1830-211
• MALS SALT-NOT survey of MIR-selected powerful radio-bright AGN at 0<z<3.5
• The influence of continuum radiation fields on hydrogen radio recombination lines
• OH in the diffuse interstellar medium: physical modelling and prospects with upcoming SKA precursor/pathfinder surveys
• Searching for the largest bound atoms in space

Cited by in corpus (2)

• A sub-ppm upper limit on the cosmological variations of the fine structure constant alpha
• Observations of Carbon Radio Recombination Lines with the NenuFAR telescope. I. Cassiopeia A and Cygnus A