Cosmo-tomography toward PKS1830-211: Variability of the quasar and of its foreground molecular absorption monitored with ALMA

Abstract

Time variability of astronomical sources provides crude information on their typical size and on the implied physical mechanisms. PKS1830-211 is a remarkable radio-bright lensed quasar with a foreground molecular absorber at z=0.89. Small-scale morphological changes in the core-jet structure of the quasar -- which is magnified by the lensing -- result in a varying illumination of the absorber screen, which in turn causes variations in the absorption profile. We aim to study the time variations of the system [...] in order to obtain constraints on both the quasar activity and small-scale structures in the ISM of the absorber. We used ALMA to monitor the submm continuum emission, together with the absorption spectra of the H2O and CH molecules, with 17 visits spread over six months in 2016. [...] From the continuum data, we followed the evolution of the flux density, flux-density ratio, spectral index, and differential polarization between the two lensed images of the quasar; all quantities show significant variations related to the intrinsic activity of the quasar. We propose a simple parametric model of a core plus a ballistic plasmon to account for the continuum evolution, from which we constrain a time delay of 25+/-3~days between lensed images. The spectral lines reveal significant variations in the foreground absorption. A PCA highlights apparent wavy time variations, possibly linked to the helical jet precession period of the quasar. From the deep averaged spectra towards the SW image, we detect the absorption of 13CH and estimate an abundance ratio of 12CH/13CH~150. We also measure the oxygen isotopic ratios, 16O/18O=65.3+/-0.7 and 18O/17O=11.5+/-0.5. Finally, we find a remarkable continuous shallow trough in the water absorption spanning a velocity interval of nearly 500 km/s. This broad absorption could be the signature of an extra-planar molecular component. [Abridged]

Accepted for publication in A&A

References in corpus (24)

• The Circumgalactic Medium
• CASA, the Common Astronomy Software Applications for Radio Astronomy
• Ultraviolet Survey of CO and H_2 in Diffuse Molecular Clouds: The Reflection of Two Photochemistry Regimes in Abundance Relationships
• Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
• Probing isotopic ratios at z = 0.89: molecular line absorption in front of the quasar PKS 1830-211
• An ALMA Early Science survey of molecular absorption lines toward PKS1830-211 -- Analysis of the absorption profiles
• Gamma-ray flaring activity from the gravitationally lensed blazar PKS 1830-211 observed by Fermi LAT
• Constraints on changes in the proton-electron mass ratio using methanol lines
• Drastic changes in the molecular absorption at redshift z=0.89 toward the quasar PKS 1830-211
• Illuminating the past 8 billion years of cold gas towards two gravitationally lensed quasars
• OH+ and H2O+ absorption toward PKS1830-211
• First detection of 13CH in the interstellar medium
• Spatially resolved carbon and oxygen isotopic ratios in NGC 253 using optically thin tracers
• Methods of Reverberation Mapping. I. Time-lag Determination by Measures of Randomness
• New molecular species at redshift z=0.89
• Detection of CH+, SH+, and their 13C- and 34S- isotopologues toward PKS1830-211
• 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
• All good things come in threes: the third image of the lensed quasar PKS1830-211
• Isotopic ratios at z=0.68 from molecular absorption lines toward B 0218+357
• Evidence for a milliparsec-separation Supermassive Binary Black Hole with quasar microlensing
• The inhomogeneous ISM toward PKS1830-211 SW - A detailed view on molecular gas at a look-back time of 7.5 Gyr
• Detection of deuterated molecules, but not of lithium hydride, in the z=0.89 absorber toward PKS1830-211
• ALMA full polarization observations of PKS1830-211 during its record-breaking flare of 2019

Cited by in corpus (4)

• SUNRISE: The rich molecular inventory of high-redshift dusty galaxies revealed by broadband spectral line surveys
• A sub-ppm upper limit on the cosmological variations of the fine structure constant alpha
• New constraints on the values of the fundamental constants at a look-back time of 7.3 Gyr
• An improved time delay from VLA and ATCA monitoring of the gravitational lens system PKS 1830-211