Diffuse molecular gas at high redshift: Detection of CO molecules and the 2175 Å dust feature at z=1.64

Abstract

We present the detection of carbon monoxide molecules (CO) at z=1.6408 towards the quasar SDSSJ160457.50+220300.5 using the VLT Ultraviolet and Visual Echelle Spectrograph. CO absorption is detected in at least two components in the first six A-X bands and one d-X(5-0) inter-band system. This is the second detection of this kind along a quasar line of sight. The CO absorption profiles are well modelled assuming a rotational excitation of CO in the range 6<Tex<16 K, which is consistent with or higher than the temperature of the CMB radiation at this redshift. We derive a total CO column density of N(CO)=4e14 cm^-2. The measured column densities of SI, MgI, ZnII, FeII and SiII indicate a dust depletion pattern typical of cold gas in the Galactic disc. The background quasar spectrum is significantly reddened (u-K~4.5 mag) and presents a pronounced 2175 A dust absorption feature at the redshift of the CO absorber. Using a control sample of ~500 quasars we find the chance probability for this feature to be spurious is ~0.3%. We show that the SED of the quasar is well fitted with a QSO composite spectrum reddened with a LMC supershell extinction law at the redshift of the absorber. It is noticeable that this quasar is absent from the colour-selected SDSS quasar sample. This demonstrates our current view of the Universe may be biased against dusty sightlines. These direct observations of carbonaceous molecules and dust open up the possibility of studying physical conditions and chemistry of diffuse molecular gas in high redshift galaxies.

6 pages, 4 figures, 2 tables, accepted for publication in A&A

References in corpus (17)

• Ultraviolet Survey of CO and H_2 in Diffuse Molecular Clouds: The Reflection of Two Photochemistry Regimes in Abundance Relationships
• Molecular hydrogen in high-redshift Damped Lyman-alpha systems: The VLT/UVES database
• The First Positive Detection of Molecular Gas in a GRB Host Galaxy
• Formation and destruction of polycyclic aromatic hydrocarbon clusters in the interstellar medium
• Direct Measurement of the Ratio of Carbon Monoxide to Molecular Hydrogen in the Diffuse Interstellar Medium
• The Magellanic zoo: Mid-infrared Spitzer spectroscopy of evolved stars and circumstellar dust in the Magellanic Clouds
• Where is the Molecular Hydrogen in Damped Lyman-Alpha Absorbers?
• Metallicity as a criterion to select H2 bearing Damped Lyman-alpha systems
• Disentangling microlensing and differential extinction in the double QSO HE0512-3329
• Detection of the 2175Å~ extinction feature and 21-cm absorption in two MgII systems at z~1.3
• HD molecules at high redshift: A low astration factor of deuterium in a solar-metallicity DLA system at z=2.418
• Missing Molecular Hydrogen and the Physical Conditions of GRB Host Galaxies
• The color excess of quasars with intervening DLA systems- Analysis of the SDSS data release five
• Presence of dust with a UV bump in massive, star-forming galaxies at 1 < z < 2.5
• Diffuse Interstellar Bands in z < 0.6 CaII Absorbers
• Probing Cosmic Dust of the Early Universe through High-Redshift Gamma-Ray Bursts
• HE 0515-4414 - an unusual sub-damped Ly alpha system revisited

Cited by in corpus (69)

• Fitting the integrated Spectral Energy Distributions of Galaxies
• Evolution of the cosmological mass density of neutral gas from Sloan Digital Sky Survey II - Data Release 7
• Molecular excitation in the Interstellar Medium: recent advances in collisional, radiative and chemical processes
• The evolution of the Cosmic Microwave Background Temperature: Measurements of TCMB at high redshift from carbon monoxide excitation
• New synthesis models of consistent extragalactic background light over cosmic time
• Breaking the Curve with CANDELS: A Bayesian Approach to Reveal the Non-Universality of the Dust-Attenuation Law at High Redshift
• A translucent interstellar cloud at z=2.69: CO, H2 and HD in the line-of-sight to SDSS J123714.60+064759.5
• The redshift evolution of escape fraction of hydrogen ionizing photons from galaxies
• UV-to-FIR analysis of Spitzer/IRAC sources in the Extended Groth Strip II: Photometric redshifts, Stellar masses and Star formation rates
• Discovery of a compact gas-rich DLA galaxy at z = 2.2: evidences for a starburst-driven outflow
• Galaxy counterparts of metal-rich damped Lyman-alpha absorbers - II. A solar-metallicity and dusty DLA at z_abs=2.58
• Obscured star formation at z = 0.84 with HiZELS: the relationship between star formation rate and H-alpha or ultra-violet dust extinction
• Molecular Hydrogen in the Damped Lyman-alpha System towards GRB 120815A at z=2.36
• The cosmic evolution of dust-corrected metallicity in the neutral gas
• Perspective: Tipping the scales - search for drifting constants from molecular spectra
• The HI Content of the Universe over the Past 10 Gyrs
• Dust-depletion sequences in damped Lyman-α absorbers: a unified picture from low-metallicity systems to the Galaxy
• Discovery of a Perseus-like cloud in the early Universe: HI-to-H2 transition, carbon monoxide and small dust grains at zabs=2.53 towards the quasar J0000+0048
• Quasars probing intermediate redshift star-forming galaxies
• The First Observations of Low Redshift Damped Lyman-alpha Systems with the Cosmic Origins Spectrograph
• Monster in the Dark: The Ultraluminous GRB 080607 and its Dusty Environment
• CO-dark molecular gas at high redshift: very large H${}_2$ content and high pressure in a low metallicity damped Lyman-alpha system
• Star formation history, dust attenuation and extragalactic background light
• Search for cold gas in z>2 damped Lyman-alpha systems: 21-cm and H_2 absorption
• Partial coverage of the Broad Line Region of Q1232+082 by an intervening H2-bearing cloud
• Search for a drifting proton--electron mass ratio from H${}_2$
• Optical/near-infrared selection of red QSOs: Evidence for steep extinction curves towards galactic centers?
• VLT/UVES observations of extremely strong intervening damped Lyman-alpha systems: Molecular hydrogen and excited carbon, oxygen and silicon at log N(HI)=22.4
• Detection of 21-cm, H2 and Deuterium absorption at z>3 along the line-of-sight to J1337+3152
• Search for cold gas in strong MgII absorbers at 0.5<z<1.5: nature and evolution of 21-cm absorbers
• The CO A-X System for Constraining Cosmological Drift of the Proton-Electron Mass Ratio
• Exploring the dust content of SDSS DR7 damped Lyman alpha systems at 2.15$\le z_{ab}<$5.2
• Parsec-scale structures and diffuse bands in a translucent interstellar medium at z 0.079
• An HST/COS survey of molecular hydrogen in DLAs & sub-DLAs at z < 1: Molecular fraction and excitation temperature
• Towards Detecting The 2175-Å Dust Feature Associated With Strong High Redshift Mg ßII Absorption Lines
• Molecular gas and star formation in an absorption-selected galaxy: Hitting the bull's eye at z = 2.46
• ALMACAL VI: Molecular gas mass density across cosmic time via a blind search for intervening molecular absorbers
• GMRT mini-survey to search for 21-cm absorption in Quasar-Galaxy Pairs at z~0.1
• Anomalously Steep Reddening Law in Quasars: An Exceptional Example Observed in IRAS14026+4341
• Cold gas and a Milky Way-type 2175 Å bump in a metal-rich and highly depleted absorption system
• The High A(V) Quasar Survey: Reddened quasi-stellar objects selected from optical/near-infrared photometry - II
• 21-cm absorption from galaxies at z ~ 0.3
• Constraint on a cosmological variation in the proton-to-electron mass ratio from electronic CO absorption
• Neutral atomic-carbon QSO absorption-line systems at z>1.5: Sample selection, HI content, reddening, and 2175 A extinction feature
• The effect of dust bias on the census of neutral gas and metals in the high-redshift Universe due to SDSS-II quasar colour selection
• A Metal-Strong and Dust-Rich Damped \lya Absorption System toward the Quasar SDSS J115705.52+615521.7
• The dust content of damped Lyman-alpha systems in the Sloan Digital Sky Survey
• Thermal Pressures in the Interstellar Medium of the Magellanic Clouds
• A Mature Dusty Star-forming Galaxy Hosting GRB080607 at z=3.036
• A Dusty Mg~II absorber Associated with the Quasar SDSS J003545.13+011441.2
• A high molecular fraction in a sub-damped absorber at z=0.56
• Incidence of HI 21-cm absorption in strong FeII systems at $0.5<z<1.5$
• A quasar hiding behind two dusty absorbers. Quantifying the selection bias of metal-rich, damped Lyman-alpha absorption systems
• HST/COS Detection of Deuterated Molecular Hydrogen in a DLA at z = 0.18
• The high A_V Quasar Survey: A z=2.027 metal-rich damped Lyman-alpha absorber towards a red quasar at z=3.21
• High Dust Depletion in Two Intervening Quasar Absorption Line Systems with the 2175-Å Extinction Bump at $z\sim 1.4$
• Quasar 2175 Å dust absorbers II: Correlation analysis and relationship with other absorption line systems
• HI 21-cm absorption from $z\sim 0.35$ strong MgII absorbers
• Analysis of carbon monoxied absorption at z=2.5 to constrain variation of the proton-to-electron mass ratio
• Estimation of physical conditions in the cold phase of the ISM in the sub-DLA system at z = 2.06 in the spectrum of the quasar J2123-0050
• Cold parsec-scale gas in a zabs~0.1 sub-DLA with disparate H2 and 21-cm absorption
• Revealing the host galaxy of a quasar 2175 Å dust absorber at z = 2.12
• Molecular hydrogen from z = 0.0963 DLA towards the QSO J1619+3342
• Searching for cosmological variation of the proton-to-electron mass ratio using a single $H_2$ system
• The 2175 Å~ Bump Features in FeLoBAL Quasars: One Indicator of MW-like Dust in the Nuclear Region of Quasar
• Ultraviolet Fe II Emission in Fainter Quasars: Luminosity Dependences, and the Influence of Environments
• Molecular hydrogen in absorption at high redshifts. Science cases for CUBES
• Probing the Interstellar Dust in Galaxies over > 10 Gyr of Cosmic History
• First detections of CO absorption in the Magellanic Clouds and direct measurement of the CO-to-H${}_2$ ratio