Related papers: Constraining fundamental constant evolution with H…
We have detected the two 18cm OH satellite lines from the $z \sim 0.247$ source PKS1413+135, the 1720 MHz line in emission and the 1612 MHz line in absorption. The 1720 MHz luminosity is $L_{\rm OH} \sim 354 L_\odot$, more than an order of…
We present a short review of the current quasar (QSO) absorption line constraints on possible variation of the fine structure constant, alpha = e^2/(hbar*c). Particular attention is paid to recent optical Keck/HIRES spectra of 49 absorption…
We present high resolution optical spectra obtained with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the Very Large Telescope (VLT) and 21-cm absorption spectra obtained with the Giant Metrewave Radio Telescope (GMRT) and the…
We report results from a Giant Metrewave Radio Telescope search for "associated" redshifted HI 21cm absorption from 24 active galactic nuclei (AGNs), at $1.1 < z < 3.6$, selected from the Caltech-Jodrell Bank Flat-spectrum (CJF) sample. 22…
We present constraints on the spacetime variation of the fine-structure constant $\alpha$ at redshifts $2.5\le z<9.5$ using JWST emission-line galaxies. The galaxy sample consists of 621 high-quality spectra with strong and narrow [O III]…
Despite much searching, redshifted decimetre and millimetre-band absorption by molecular gas remains very rare, limited to just six systems at z > 0.05. Detection of these transitions can yield precise diagnostics of the conditions of the…
We report on WSRT observations of HI and OH absorption at z=0.885 towards the radio lens PKS 1830-21, mm wave transitions of several molecular species have already been observed at this redshift. At mm wavelengths the source structure is…
We report a deep search for redshifted HI 21 cm emission from three damped and sub-damped Lyman-$\alpha$ absorbers (DLAs) at $z \approx 0.1$ with the Green Bank Telescope (GBT). No evidence for a redshifted HI 21 cm emission signal was…
We present an analysis of the evolution of the Ly alpha absorption lines in the redshift interval 0.0 to \sim 1.5 based upon a sample of 987 lines identified in the spectra of 63 QSOs obtained with the Faint Object Spectrograph on the…
We present Giant Metrewave Radio Telescope (GMRT) observations of redshifted HI 21cm absorption in two low redshift (z=0.2212, z=0.0912) damped Lyman-alpha systems seen towards the gigahertz peaked source OI 363 (z_em = 0.630). The object…
Attempts to measure the variability of the fine structure constant alpha over cosmological time, using spectra of high redshift quasars have produced conflicting results. We use the Many Multiplet (MM) method with Mg II and Fe II lines on…
We report on sensitive observations of the CO(7-6) and CI(2-1) transitions in the z=2.79 QSO host galaxy RXJ0911.4+0551 using the IRAM Plateau de Bure interferometer (PdBI). Our extremely high signal to noise spectra combined with the…
The offsets between the radial velocities of the rotational transitions of carbon monoxide and the fine structure transitions of neutral and singly ionized carbon are used to test the hypothetical variation of the fine structure constant,…
The interstellar hydride hydroxyl (OH) is a potential tracer of CO-dark molecular gas. We present new absorption line observations of OH at 18-cm wavelength towards four continuum sources. We compare these to the [CII] line at 1.9 THz…
We present measurements of absorption by the 21cm hyperfine transition of neutral hydrogen toward radio sources at substantial look-back times. These data are used in combination with observations of rotational transitions of common…
We present evidence for variations in the fine-structure constant from Keck/HIRES spectra of 143 quasar absorption systems over the redshift range 0.2 < z_abs < 4.2. This includes 15 new systems, mostly at high-z (z_abs > 1.8). Our most…
Recent detections of high-redshift absorption by both atomic hydrogen and molecular gas in the radio spectra of quasars have provided a powerful tool to measure possible temporal and spatial variations of physical `constants' in the…
We have used the Westerbork Synthesis Radio Telescope to detect HI 21cm absorption at $z \sim 0.7645$ in the gravitational lens system towards PMN J0134-0931. The 21cm profile has two broad components, with peak optical depths of $0.047 \pm…
OH absorption is currently the only viable way to detect OH molecules in non-masing galaxies at cosmological distances. There have been only 6 such detections at z>0.05 to date and so it is hard to put a statistically robust constraint on…
We investigate the effect of variation in the value of the fine structure constant at high redshifts (recombination > z > 30) on the absorption of the cosmic microwave background (CMB) at 21 cm hyperfine transition of the neutral atomic…