Abstract
Absorption by carbon monoxide in the spectrum of quasar SDSS J000015.16+004833.2 is investigated in order to derive a constraint on the temporal variation of the proton-to-electron mass ...ratio, μ. The spectrum was recorded using Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph, and it was partially corrected for long-range wavelength scale distortions using the supercalibration technique. Eight vibrational CO singlet–singlet bands belonging to the A1Π–X1Σ+ electronic absorption system, and the perturbing d3Δ–X1Σ+(5, 0) singlet–triplet band are detected in the damped Lyman α system at zabs ≃ 2.52. The spectra are modelled using a comprehensive fitting technique, resulting in a final value of Δμ/μ = (1.8 ± 2.2stat ± 0.4syst) × 10−5, which is consistent with no variation over a look-back time of ∼11.2 Gyr.
Abstract
We present high-resolution optical spectra obtained with the Ultraviolet and Visual Echelle Spectrograph at the Very Large Telescope and 21-cm absorption spectra obtained with the Giant ...Metrewave Radio Telescope and the Green Bank Telescope of five quasars along the line of sight of which 21-cm absorption systems at 1.17 < z < 1.56 have been detected previously. We also present milliarcsecond-scale radio images of these quasars obtained with the Very Large Baseline Array. We use the data on four of these systems to constrain the time variation of x ≡ g
pα2/μ, where g
p is the proton gyromagnetic factor, α is the fine structure constant and μ is the proton-to-electron mass ratio. We carefully evaluate the systematic uncertainties in redshift measurements using cross-correlation analysis and repeated Voigt profile fitting. In both cases, we also confirm our results by analysing optical spectra obtained with the Keck telescope. We find the weighted and the simple means of Δx/x to be, respectively, −(0.1 ± 1.3) × 10−6 and (0.0 ± 1.5) × 10−6 at the mean redshift of 〈z〉 = 1.36 corresponding to a look-back time of ∼9 Gyr. This is the most stringent constraint ever obtained on Δx/x. If we only use the two systems towards quasars unresolved at milliarcsecond scales, we get the simple mean of Δx/x = +(0.2 ± 1.6) × 10−6. Assuming the constancy of other constants, we get Δα/α = (0.0 ± 0.8) × 10−6, which is a factor of 2 better than the best constraints obtained so far using the many-multiplet method. On the other hand, assuming that α and g
p have not varied we derive Δμ/μ = (0.0 ± 1.5) × 10−6 which is again the best limit ever obtained on the variation of μ over this redshift range. Using independent constraints on Δα/α at z < 1.8 and Δμ/μ at z ∼ 0.7 available in the literature, we get Δg
p/g
p ≤ 3.5 × 10−6(1σ).
We present spectroscopic observations of six high redshift (z
em > 2) quasars, which have been selected for their Lyman α (Lyα) emission region being only partially covered by a strong proximate (z
...abs ∼ z
em) coronagraphic damped Lyα system (DLA). We detected spatially extended Lyα emission envelopes surrounding these six quasars, with projected spatial extent in the range 26 ≤ d
Lyα ≤ 51 kpc. No correlation is found between the quasar ionizing luminosity and the Lyα luminosity of their extended envelopes. This could be related to the limited covering factor of the extended gas and/or due to the AGN being obscured in other directions than towards the observer. Indeed, we find a strong correlation between the luminosity of the envelope and its spatial extent, which suggests that the envelopes are probably ionized by the AGN. The metallicity of the coronagraphic DLAs is low and varies in the range −1.75 < Si/H < −0.63. Highly ionized gas is observed to be associated with most of these DLAs, probably indicating ionization by the central AGN. One of these DLAs has the highest Al iii/Si ii ratio ever reported for any intervening and/or proximate DLA. Most of these DLAs are redshifted with respect to the quasar, implying that they might represent infalling gas probably accreted on to the quasar host galaxies through filaments.
We present a detailed study of the QSO-galaxy pair SDSS J163956.35+112758.7 (z
q = 0.993) and SDSS J163956.38+112802.1 (z
g = 0.079) based on observations carried out using the Giant Metrewave Radio ...Telescope (GMRT), the Very Large Baseline Array (VLBA), the Sloan Digital Sky Survey and the ESO New Technology Telescope. We show that the interstellar medium of the galaxy probed by the QSO line of sight has near-solar metallicity 12+log(O/H) = 8.47 ± 0.25 and dust extinction E(B − V) ∼ 0.83 ± 0.11 typical of what is usually seen in translucent clouds. We report the detection of absorption in the λ6284 diffuse interstellar band (DIB) with a rest equivalent width of 1.45 ± 0.20 Å. Our GMRT spectrum shows a strong 21-cm absorption at the redshift of the galaxy with an integrated optical depth of 15.70 ± 0.13 km s−1. Follow-up VLBA observations show that the background radio source is resolved into three components with a maximum projected separation of 89 pc at the redshift of the galaxy. One of these components is too weak to provide useful 21-cm H i information. The integrated H i optical depth towards the other two components are higher than that measured in our GMRT spectrum and differ by a factor 2. By comparing the GMRT and VLBA spectra we show the presence of structures in the 21-cm optical depth on parsec scales. We discuss the implications of such structures for the spin-temperature measurements in high-z damped Lyman α systems. The analysis presented here suggests that this QSO-galaxy pair is an ideal target for studying the DIBs and molecular species using future observations in optical and radio wavebands.
Abstract
We present optical spectroscopic and milliarcsecond-scale radio continuum observations of the quasar M1540–1453 (
z
em
= 2.104 ± 0.002) that show associated H
i
21 cm absorption at
z
abs
= ...2.1139. At subkiloparsec scales, the powerful radio source with 1.4 GHz luminosity of 5.9 × 10
27
W Hz
−1
shows Fanaroff–Riley class I morphology caused by the interaction with dense gas within 70 pc of the active galactic nucleus (AGN). Interestingly, while there are indications for the presence of absorption from low-ionization species like Fe
ii
, Si
ii,
and Si
iii
in the optical spectrum, the expected strong damped Ly
α
absorption is not detected at the redshift of the H
i
21 cm absorber. In comparison to typical high-
z
quasars, the Ly
α
emission line is much narrower. The “ghostly” nature of the H
i
Ly
α
absorber partially covering the broad-line region of extent 0.05 pc and the detection of widespread H
i
21 cm absorption covering the diffuse radio source (extent >425 pc) imply the presence of a large clumpy H
i
halo, which may have been blown by the jet–interstellar medium (ISM) interaction. Further observations are needed to confirm the ghostly nature of the Ly
α
absorber and obtain a better understanding of the role played by the jet–ISM interaction in shaping the radio morphology of this powerful AGN. The study showcases how joint radio and optical analysis can shed light on the gaseous environment and origin of radio morphology in AGNs at high redshifts, when these are still the assembly sites of giant galaxies.
We present an accurate analysis of the H2 absorption lines from the z
abs ∼ 2.4018 damped Lyα system towards HE 0027−1836 observed with the Very Large Telescope Ultraviolet and Visual Echelle ...Spectrograph (VLT/UVES) as a part of the European Southern Observatory Large Programme 'The UVES large programme for testing fundamental physics' to constrain the variation of proton-to-electron mass ratio, μ ≡ m
p
/m
e
. We perform cross-correlation analysis between 19 individual exposures taken over three years and the combined spectrum to check the wavelength calibration stability. We notice the presence of a possible wavelength-dependent velocity drift especially in the data taken in 2012. We use available asteroids spectra taken with UVES close to our observations to confirm and quantify this effect. We consider single- and two-component Voigt profiles to model the observed H2 absorption profiles. We use both linear regression analysis and Voigt profile fitting where Δμ/μ is explicitly considered as an additional fitting parameter. The two-component model is marginally favoured by the statistical indicators and we get Δμ/μ = −2.5 ± 8.1stat ± 6.2sys ppm. When we apply the correction to the wavelength-dependent velocity drift, we find Δμ/μ = −7.6 ± 8.1stat ± 6.3sys ppm. It will be important to check the extent to which the velocity drift we notice in this study is present in UVES data used for previous Δμ/μ measurements.
ABSTRACT
We present MeerKAT Absorption Line Survey (MALS) observations of the H i gas in the Klemola 31 galaxy group (z = 0.029), located along the line of sight to the radio-loud quasar PKS 2020−370 ...(z = 1.048). Four galaxies of the group are detected in H i emission, and H i absorption is also detected in front of PKS 2020−370 in Klemola 31A. The emission and absorption are somewhat compensating on the line of sight of the quasar, and the derived column density of the absorption appears underestimated, with respect to the neighbouring emission. A symmetric tilted-ring model of Klemola 31A, assuming the absorbing gas in regular rotation in the plane, yields a rather high spin temperature of 530 K. An alternative interpretation is that the absorbing gas is extra-planar, which will also account for its non-circular motion. The Na i/Ca ii ratio also suggests that the absorbing gas is unrelated to cold H i disc. Two of the galaxies in the Klemola group are interacting with a small companion, and reveal typical tidal tails, and velocity perturbations. Only one of the galaxies, ESO 400−13, reveals a strong H i deficiency, and a characteristic ram-pressure stripping, with a total asymmetry in the distribution of its gas. Since a small galaxy group as Klemola 31 is not expected to host a dense intra-group gas, this galaxy must be crossing the group at a very high velocity, mostly in the sky plane.
We present a preparatory spectroscopic survey to identify radio-bright, high-redshift quasars for the MeerKAT Absorption Line Survey. The candidates have been selected on the basis of a single flux ...density limit at 1.4 GHz (>200 mJy), together with mid-infrared color criteria from the Wide-field Infrared Survey Explorer. Through spectroscopic observations using the Nordic Optical Telescope, we identify 72 quasars out of 99 candidates targeted. We measure the spectroscopic redshifts based on characteristic, broad emission lines present in the spectra. Of these 72 quasars, 64 and 48 objects are at sufficiently high redshift (z > 0.6 and z > 1.4) to be used for the L-band and UHF-band spectroscopic follow-up with the Square Kilometre Array precursor in South Africa: the MeerKAT.
ABSTRACT
We use spatially resolved spectroscopy of a distant giant gravitational arc to test orientation effects on Mg ii absorption equivalent width (EW) and covering fraction (〈κ〉) in the ...circumgalactic medium of a foreground star-forming galaxy (G1) at z ∼ 0.77. Forty-two spatially-binned arc positions uniformly sample impact parameters (D) to G1 between 10 and 30 kpc and azimuthal angles α between 30° and 90° (minor axis). We find an EW-D anticorrelation, akin to that observed statistically in quasar absorber studies, and an apparent correlation of both EW and 〈κ〉 with α, revealing a non-isotropic gas distribution. In line with our previous results on Mg ii kinematics suggesting the presence of outflows in G1, at minimum a simple 3D static double-cone model (to represent the trace of bipolar outflows) is required to recreate the EW spatial distribution. The D and α values probed by the arc cannot confirm the presence of a disc, but the data highly disfavour a disc alone. Our results support the interpretation that the EW-α correlation observed statistically using other extant probes is partly shaped by bipolar metal-rich winds.
Abstract
The MeerKAT Absorption Line Survey (MALS) has observed 391 telescope pointings at the
L
band (900–1670 MHz) at
δ
≲ +20°. We present radio continuum images and a catalog of 495,325 (240,321) ...radio sources detected at a signal-to-noise ratio (S/N) > 5 over an area of 2289 deg
2
(1132 deg
2
) at 1006 MHz (1381 MHz). Every MALS pointing contains a central bright radio source (
S
1 GHz
≳ 0.2 Jy). The median spatial resolution is 12″ (8″). The median rms noise away from the pointing center is 25
μ
Jy beam
−1
(22
μ
Jy beam
−1
) and is within ∼15% of the achievable theoretical sensitivity. The flux density scale ratio and astrometric accuracy deduced from multiply observed sources in MALS are <1% (8% scatter) and 1″, respectively. Through comparisons with NVSS and FIRST at 1.4 GHz, we establish the catalog’s accuracy in the flux density scale and astrometry to be better than 6% (15% scatter) and 0.″8, respectively. The median flux density offset is higher (9%) for an alternate beam model based on holographic measurements. The MALS radio source counts at 1.4 GHz are in agreement with literature. We estimate spectral indices (
α
) of a subset of 125,621 sources (S/N > 8), confirm the flattening of spectral indices with decreasing flux density, and identify 140 ultra-steep-spectrum (
α
< −1.3) sources as prospective high-
z
radio galaxies (
z
> 2). We have identified 1308 variable and 122 transient radio sources comprising primarily active galactic nuclei that demonstrate long-term (26 yr) variability in their observed flux densities. The MALS catalogs and images are publicly available at
https://mals.iucaa.in
.
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