A study of submillimeter methanol absorption toward PKS1830-211: Excitation, invariance of the proton-electron mass ratio, and systematics

Abstract

Methanol is an important tracer to probe physical and chemical conditions in the interstellar medium of galaxies. Methanol is also the most sensitive target molecule for probing potential space-time variations of the proton-electron mass ratio, mu, a dimensionless constant of nature. We present an extensive ALMA study of the strongest submillimeter absorption lines of methanol [...] in the z=0.89 molecular absorber toward PKS1830-211, the only high-redshift object in which methanol has been detected. Our goals are to constrain the excitation of the methanol lines and to investigate the cosmological invariance of mu based on their relative kinematics. [...] We explore methanol excitation by running the non local thermal equilibrium radiative transfer code RADEX [...] The excitation analysis points to a cool (~10-20 K) and dense (~10^{4-5} cm-3) methanol gas. [...] In addition, we measure an abundance ratio A/E = 1.0 +/- 0.1, an abundance ratio CH3OH/H2 ~ 2 x 10^{-8}, and a 12CH3OH/13CH3OH ratio 62 +/- 3. Our analysis shows that the bulk velocities of the different transitions are primarily correlated with the observing epoch due to morphological changes in the background quasar's emission. There is a weaker correlation between bulk velocities and the lower level energies of the transitions, which could be a signature of temperature-velocity gradients in the absorbing gas. As a result, we do not find evidence for variations of mu, and we estimate Dmu/mu = (-1.8 +/- 1.2) x 10^{-7} at 1sigma from our multivariate linear regression. We set a robust upper limit | \Dmu/mu | < 3.6 x 10^{-7} (3sigma) for the invariance of mu at a look-back time of half the present age of the Universe. Our analysis highlights that systematics need to be carefully taken into account in future radio molecular absorption studies aimed at testing Dmu/mu below the 10^{-7} horizon. (Abridged)

arXiv commentAccepted for publication in A&A

References in corpus (61)

• A computer program for fast non-LTE analysis of interstellar line spectra
• Search for New Physics with Atoms and Molecules
• The Cologne Database for Molecular Spectroscopy, CDMS, in the Virtual Atomic and Molecular Data Centre, VAMDC
• Varying constants, Gravitation and Cosmology
• Non-thermal desorption from interstellar dust grains via exothermic surface reactions
• Frequency ratio of two optical clock transitions in ${}^{171}$Yb${}^{+}$ and constraints on the time-variation of fundamental constants
• Improved limit on a temporal variation of $m_p/m_e$ from comparisons of Yb${}^{+}$ and Cs atomic clocks
• Space-Time Variation of Physical Constants and Relativistic Corrections in Atoms
• UVMULTIFIT: A versatile tool for fitting astronomical radio interferometric data
• Molecules at z=0.89: A 4-mm-rest-frame absorption line survey toward PKS 1830-211
• Strong Limit on a Variable Proton-to-Electron Mass Ratio from Molecules in the Distant Universe
• Enhanced sensitivity to time-variation of m_p/m_e in the inversion spectrum of ammonia
• A precise and accurate determination of the cosmic microwave background temperature at z=0.89
• The UVES Large Program for Testing Fundamental Physics II: Constraints on a Change in μ Towards Quasar HE 0027-1836
• Keck telescope constraint on cosmological variation of the proton-to-electron mass ratio
• Constraining changes in the proton-electron mass ratio with inversion and rotational lines
• Impact of instrumental systematic errors on fine-structure constant measurements with quasar spectra
• Robust Constraint on a Drifting Proton-to-Electron Mass Ratio at z=0.89 from Methanol Observation at Three Radio Telescopes
• The density, the cosmic microwave background, and the proton-to-electron mass ratio in a cloud at redshift 0.9
• Wavelength Accuracy of the Keck HIRES Spectrograph and Measuring Changes in the Fine Structure Constant
• Methanol as a tracer of fundamental constants
• The redshift of the gravitationally lensed radio source PKS1830-211
• PKS 1830-211: A Face-On Spiral Galaxy Lens
• Probing isotopic ratios at z = 0.89: molecular line absorption in front of the quasar PKS 1830-211
• First constraint on cosmological variation of the proton-to-electron mass ratio from two independent telescopes
• Constraining the variation of fundamental constants using 18cm OH lines
• 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
• Search for a drifting proton--electron mass ratio from H${}_2$
• 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
• 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
• Non-thermal desorption of complex organic molecules: Cosmic-ray sputtering of CH3OH embedded in CO2 ice
• Detection of chloronium and measurement of the 35Cl/37Cl isotopic ratio at z=0.89 toward PKS1830-211
• OH+ and H2O+ absorption toward PKS1830-211
• Conjugate 18cm OH Satellite Lines at a Cosmological Distance
• Changes in the measured image separation of the gravitational lens system, PKS 1830-211
• Detection of 36 GHz class I methanol maser emission towards NGCS253
• Helical Jet in the Gravitationally Lensed Blazar PKS1830-211
• Characterization of methanol as a magnetic field tracer in star-forming regions
• First cosmological constraints on the proton-to-electron mass ratio from observations of rotational transitions of methanol
• New molecular species at redshift z=0.89
• Detection of CH+, SH+, and their 13C- and 34S- isotopologues toward PKS1830-211
• Detection of extragalactic CF+ toward PKS1830-211 -- Chemical differentiation in the absorbing gas
• Practical Limitations on Astrophysical Observations of Methanol to Investigate Variations in the Proton-to-Electron Mass Ratio
• Testing the variability of the proton-to-electron mass ratio from observations of methanol in the dark cloud core L1498
• PKS1830-211: OH and HI at z=0.89 and the first MeerKAT UHF spectrum
• Detection of 6.7 GHz methanol absorption towards hot corinos
• All good things come in threes: the third image of the lensed quasar PKS1830-211
• 6.7 GHz methanol absorption toward the Seyfert 2 galaxy NGC 3079
• Formaldehyde Anti-Inversion at z=0.68 in the Gravitational Lens B0218+357
• 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
• Detection of deuterated molecules, but not of lithium hydride, in the z=0.89 absorber toward PKS1830-211
• 36 GHz methanol lines from nearby galaxies: maser or quasi-thermal emission?
• On Measuring the CMB Temperature at Redshift 0.89
• Methanol absorption in PKS B1830-211 at milliarcsecond scales
• Study of Temporal and Spectral variability for Blazar PKS 1830-211 with Multi-Wavelength Data
• ALMA full polarization observations of PKS1830-211 during its record-breaking flare of 2019

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• ALCHEMI: an ALMA Comprehensive High-resolution Extragalactic Molecular Inventory. Survey presentation and first results from the ACA array
• Near-to mid-IR spectral purity transfer with a tunable frequency comb: methanol frequency metrology over a record frequency span
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• H2CN/H2NC abundance ratio: a new potential temperature tracer for the interstellar medium
• Discovery of Hydrogen Radio Recombination Lines at z=0.89 towards PKS 1830-211
• Complex Organic Molecules towards the central molecular zone of NGC 253
• Carbonates and ices in the $z=0.89$ galaxy-absorber towards PKS 1830-211 and within star-forming regions of the Milky Way
• A sub-ppm upper limit on the cosmological variations of the fine structure constant alpha
• Varying fundamental constants cosmography
• New constraints on the values of the fundamental constants at a look-back time of 7.3 Gyr