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ABSTRACT: We have previously presented 5.7 σ evidence for a smaller αat redshifts 0.2 < zabs < 3.7 from a sample of 128 Keck/HIRES quasar absorption systems: Δα/α = (-0.57 ± 0.10) x10-5. A non-zero <Δα/α manifests itself as a distinct pattern of shifts in the measured absorption line wavelengths. The statistical
error is now small: we do detect small line shifts in the HIRES data. Whether these shifts are due to systematic errors or
due to real variation in α is now the central question. Here we summarize the two potentially most important systematic effects:
atmospheric dispersion and isotopic abundance evolution. Previously, these have been difficult to quantify/model but here
we find that neither of them can explain our results. Furthermore, the HIRES spectra themselves contain no evidence for these
effects. Independent measurements of Δα/α with a different telescope and spectrograph are now crucial if we are to rule out
or confirm the present evidence for a variable α.
Astrophysics and Space Science 04/2012; 283(4):577-582. · 1.69 Impact Factor
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ABSTRACT: By comparing the widths of absorption lines from OI, SiII and FeII in the
redshift z=2.076 single-component damped Lyman alpha absorption system in the
spectrum of Q2206-199 we establish that these absorption lines arise in Warm
Neutral Medium gas at ~12000 +/- 3000K. This is consistent with thermal
equilibrium model estimates of ~ 8000K for the Warm Neutral Medium in galaxies,
but not with the presence of a significant cold component. It is also
consistent with, but not required by, the absence of CII* fine structure
absorption in this system. Some possible implications concerning abundance
estimates in narrow-line WNM absorbers are discussed.
02/2012;
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ABSTRACT: We previously reported Keck telescope observations suggesting a smaller value of the fine structure constant α at high redshift. New Very Large Telescope (VLT) data, probing a different direction in the Universe, shows an inverse evolution; α increases at high redshift. Although the pattern could be due to as yet undetected systematic effects, with the systematics as presently understood the combined data set fits a spatial dipole, significant at the 4.2 σ level, in the direction right ascension 17.5 ± 0.9 h, declination -58 ± 9 deg. The independent VLT and Keck samples give consistent dipole directions and amplitudes, as do high and low redshift samples. A search for systematics, using observations duplicated at both telescopes, reveals none so far which emulate this result.
Physical Review Letters 11/2011; 107(19):191101. · 7.37 Impact Factor
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ABSTRACT: We have used GIM2D to quantify the morphological properties of 40
intermediate redshift MgII absorption-selected galaxies (0.03<Wr(2796)<2.9
Ang), imaged with WFPC-2/HST, and compared them to the halo gas properties
measured form HIRES/Keck and UVES/VLT quasar spectra. We find that as the
quasar-galaxy separation, D, increases the MgII equivalent decreases with large
scatter, implying that D is not the only physical parameter affecting the
distribution and quantity of halo gas. Our main result shows that inclination
correlates with MgII absorption properties after normalizing out the
relationship (and scatter) between the absorption properties and D. We find a
4.3 sigma correlation between Wr(2796) and galaxy inclination, normalized by
impact parameter, i/D. Other measures of absorption optical depth also
correlate with i/D at greater than 3.2 sigma significance. Overall, this result
suggests that MgII gas has a co-planer geometry, not necessarily disk-like,
that is coupled to the galaxy inclination. It is plausible that the absorbing
gas arises from tidal streams, satellites, filaments, etc., which tend to have
somewhat co-planer distributions. This result does not support a picture in
which MgII absorbers with Wr(2796)<1A are predominantly produced by
star-formation driven winds. We further find that; (1) MgII host galaxies have
quantitatively similar bulge and disk scale length distribution to field
galaxies at similar redshifts and have a mean disk and bulge scale length of
3.8kpc and 2.5kpc, respectively; (2) Galaxy color and luminosity do not
correlate strongly with absorption properties, implying a lack of a connection
between host galaxy star formation rates and absorption strength; (3)
Parameters such as scale lengths and bulge-to-total ratios do not significantly
correlate with the absorption parameters, suggesting that the absorption is
independent of galaxy size or mass.
06/2011;
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ABSTRACT: We have undertaken a search for millimetre-wave band absorption (through the
CO and HCO+ rotational transitions) in the host galaxies of reddened radio
sources (z = 0.405-1.802). Despite the colour selection (optical-near infrared
colours of V - K > 5 in all but one source), no absorption was found in any of
the eight quasars for which the background continuum flux was detected. On the
basis of the previous (mostly intervening) H2 and OH detections, the limits
reached here and in some previous surveys should be deep enough to detect
molecular absorption according to their V - K colours. However, our survey
makes the assumption that the reddening is associated with dust close to the
emission redshift of the quasar and that the narrow millimetre component of
this emission is intercepted by the compact molecular cores. By using the known
millimetre absorbers to define the colour depth and comparing this with the
ultra-violet luminosities of the sources, we find that, even if these
assumptions are valid, only twelve of the forty objects (mainly from this work)
are potentially detectable. This is assuming an excitation temperature of 10 K
at z=0, with the number decreasing with increasing temperatures (to zero
detectable at 100 K).
06/2011;
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ABSTRACT: A high signal-to-noise spectrum covering the largest number of hydrogen lines (90 H(2) lines and 6 HD lines) in a high-redshift object was analyzed from an observation along the sight line to the bright quasar source J2123-005 with the Ultraviolet and Visual Echelle Spectrograph on the European Southern Observatory Very Large Telescope (Paranal, Chile). This delivers a constraint on a possible variation of the proton-to-electron mass ratio of Δμ/μ=(8.5 ± 3.6(stat) ± 2.2(syst))×10(-6) at redshift z(abs) = 2.059, which agrees well with a recently published result on the same system observed at the Keck telescope yielding Δμ/μ=(5.6 ± 5.5(stat) ± 2.9(syst))×10(-6). Both analyses used the same robust absorption line fitting procedures with detailed consideration of systematic errors.
Physical Review Letters 05/2011; 106(18):180802. · 7.37 Impact Factor
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ABSTRACT: From a survey for redshifted HI 21-cm and OH 18-cm absorption in the hosts of a sample of radio galaxies and quasars, we detect HI in three of the ten and OH in none of the fourteen sources for which useful data were obtained. As expected from our recent result, all of the 21-cm detections occur in sources with ultra-violet continuum luminosities of L < 10^23 W/Hz. At these "moderate" luminosities, we also obtain four non-detections, although, as confirmed by the equipartition of detections between the type-1 and type-2 objects, this near-50% detection rate cannot be attributed to unified schemes of active galactic nuclei (AGN). All of our detections are at redshifts of z < 0.67, which, in conjunction with our faint source selection, biases against UV luminous objects. The importance of ultra-violet luminosity (over AGN type) in the detection of 21-cm is further supported by the non-detections in the two high redshift z ~ 3.6 - 3.8 radio galaxies, which are both type-2 objects, while having L > 10^23 W/Hz. Our 21-cm detections in combination with those previously published, give a total of eight (associated and intervening) HI absorbing sources searched and undetected in OH. Using the detected 21-cm line strengths to normalise the limits, we find that only two of these eight may have been searched sufficiently deeply in OH, although even these are marginal. Comment: 10 pages, submitted to MNRAS
12/2010;
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ABSTRACT: Theories unifying gravity with other interactions suggest spatial and temporal variation of fundamental "constants" in the Universe. A change in the fine structure constant, alpha, could be detected via shifts in the frequencies of atomic transitions in quasar absorption systems. Recent studies using 140 absorption systems from the Keck telescope and 153 from the Very Large Telescope, suggest that alpha varies spatially. That is, in one direction on the sky alpha seems to have been smaller at the time of absorption, while in the opposite direction it seems to have been larger. To continue this study we need accurate laboratory measurements of atomic transition frequencies. The aim of this paper is to provide a compilation of transitions of importance to the search for alpha variation. They are E1 transitions to the ground state in several different atoms and ions, with wavelengths ranging from around 900 - 6000 A, and require an accuracy of better than 10^{-4} A. We discuss isotope shift measurements that are needed in order to resolve systematic effects in the study. The coefficients of sensitivity to alpha-variation (q) are also presented. Comment: Includes updated version of the "alpha line" list
11/2010;
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ABSTRACT: [ABRIDGED] We examine the velocity structure in the gas associated with \ion{H}{1} in the damped Ly$\alpha$ absorption system at redshift $z=1.7764$ towards the QSO $1331+170$ using 21cm data, optical and STIS spectra. We find at least two, and possibly three, components showing \ion{C}{1} lines. One of these has Doppler parameter $b=0.55${\kms}, corresponding to a kinetic temperature of 220K if the broadening is thermal. We re-examine the H$_2$ analysis undertaken by \citet{Cui05} using the neutral carbon velocity structure, and find a model which is, consistent with a mixture of collisional and background radiation excitation of the observed H$_2$ rotational levels. For singly ionized heavy elements we find eight components covering a velocity range of $\sim 110$ {\kms}. The \ion{H}{1} structure is expected to follow some combination of the singly ionized and neutral gas, but the 21cm absorption profile is considerably different. This may be because of the different extent and brightness distributions of the radio and optical background sources, and so the spin temperature derived by comparing the Ly$\alpha$ and 21cm line strengths has little physical meaning. The neutral and singly ionized heavy element line profiles also show significant differences, and so the dominant components in each appear to be physically distinct. Attempts to use the range of atomic masses to separate thermal and turbulent components of their Doppler widths were not generally successful. The velocity structure in all ionization stages up to $+3$, apart from the neutral heavy elements, is sufficiently complex that it is difficult to separate out the corresponding velocity components for different ionization levels and determine their column densities. Comment: 49 pages, 8 figures, 6 tables. Accepted for publication in MNRAS
10/2010;
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ABSTRACT: We report on a variable high-velocity narrow absorption line outflow in the redshift 2.3 quasar J2123-0050. Five distinct outflow systems are detected with velocity shifts from -9710 to -14,050 km/s and CIV 1548,1551 line widths of FWHM = 62-164 km/s. These data require five distinct outflow structures with similar kinematics, physical conditions and characteristic sizes of order 0.01-0.02 pc. The most likely location is ~5 pc from the quasar. The coordinated line variations in <0.63 yr (rest) are best explained by global changes in the outflow ionization caused by changes in the quasar's ionizing flux. The absence of strong X-ray absorption shows that radiative shielding is not needed to maintain the moderate ionizations and therefore, apparently, it is not needed to facilitate the radiative acceleration to high speeds. The kinetic energy yield of this flow is at least two orders of magnitude too low to be important for feedback to the host galaxy's evolution. Comment: 20 pages. In press with MNRAS
08/2010;
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J. Tumlinson,
A. L. Malec,
R. F. Carswell, M. T. Murphy,
R. Buning,
N. Milutinovic,
S. L. Ellison,
J. X. Prochaska,
R. A. Jorgenson,
W Ubachs,
A. M. Wolfe
[show abstract]
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ABSTRACT: We report two detections of deuterated molecular hydrogen (HD) in QSO absorption-line systems at $z > 2$. Toward J2123-0500, we find $N$(HD) $= 13.84 \pm 0.2$ for a sub-DLA with metallicity $\simeq 0.5Z_{\odot}$ and $N$(H$_2$) = $17.64 \pm 0.15$ at $z = 2.0594$. Toward FJ0812+32, we find $N$(HD) $= 15.38 \pm 0.3$ for a solar-metallicity DLA with $N$(H$_2$) = $19.88 \pm 0.2$ at $z = 2.6265$. These systems have ratios of HD to H$_2$ above that observed in dense clouds within the Milky Way disk and apparently consistent with a simple conversion from the cosmological ratio of D/H. These ratios are not readily explained by any available model of HD chemistry and there are no obvious trends with metallicity or molecular content. Taken together, these two systems and the two published $z > 2$ HD-bearing DLAs indicate that HD is either less effectively dissociated or more efficiently produced in high-redshift interstellar gas, even at low molecular fraction and/or solar metallicity. It is puzzling that such diverse systems should show such consistent HD/H$_2$ ratios. Without clear knowledge of all the aspects of HD chemistry that may help determine the ratio HD/H$_2$, we conclude that these systems are potentially more revealing of gas chemistry than of D/H itself and that it is premature to use such systems to constrain D/H at high-redshift. Comment: accepted for publication in ApJ Letters, 5 pages emulate ApJ text
06/2010;
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ABSTRACT: (Abridged) We performed a spectroscopic galaxy survey, complete to m<20.3 (L_B>0.15L_B* at z=0.3), within 100x100" of the quasar Q1127-145 (z=1.18). The VLT/UVES quasar spectrum contains three z<0.33 MgII absorption systems. We obtained eight new galaxy redshifts, adding to the four previously known, and galaxy star formation rates and metallicities were computed where possible. A strong MgII system [W_r(2796)=1.8A], which is a known DLA, had three previously identified galaxies; we found two additional galaxies associated with this system. These five galaxies form a group with diverse properties, such as a luminosity range of 0.04<L_B<0.63L_B*, an impact parameter range of 17<D<241kpc and velocity dispersion of 115km/s. The DLA group galaxy redshifts span beyond the 350km/s velocity spread of the metallic absorption lines of the DLA itself. The two brightest group galaxies have SFRs of a few Msun/yr and should not have strong winds. We have sufficient spectroscopic information to directly compare three of the five group galaxies' (emission-line) metallicities with the DLA (absorption) metallicity: the DLA metallicity is 1/10th solar, substantially lower than the three galaxies' which range between less than 1/2 solar to solar metallicity. HST/WFPC-2 imaging shows perturbed morphologies for the three brightest group galaxies, with tidal tails extending 25kpc. We favor a scenario where the DLA absorption originates from tidal debris in the group environment. Another absorber exhibits weak MgII absorption [W_r(2796)=0.03A] and had a previously identified galaxy at a similar redshift. We have identified a second galaxy associated with this system. Both galaxies have solar metallicities and unperturbed morphologies. The SFR of one galaxy is much lower than expected for strong outflows. Finally, we have identified five galaxies at large impact parameters with no associated MgII absorption. Comment: 15 pages, 7 figures, 5 tables. Accepted for publication in MNRAS.
03/2010;
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R. Chornock,
A. V. Filippenko,
W Li,
G. H. Marion,
R. J. Foley,
M. Modjaz,
M. Rafelski,
G. D. Becker,
W. H. de Vries,
P. Garnavich, [......],
A. L. Malec,
E. C. Moran, M. T. Murphy,
R. J. Rudy,
R. W. Russell,
J. M. Silverman,
T. N. Steele,
A. Stockton,
A. M. Wolfe,
C. E. Woodward
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ABSTRACT: Supernova (SN) 2008ax in NGC 4490 was discovered within hours after shock
breakout, presenting the rare opportunity to study a core-collapse SN beginning
with the initial envelope-cooling phase immediately following shock breakout.
We present an extensive sequence of optical and near-infrared spectra, as well
as three epochs of optical spectropolarimetry. Our initial spectra, taken two
days after shock breakout, are dominated by hydrogen Balmer lines at high
velocity. However, by maximum light, He I lines dominated the optical and
near-infrared spectra, which closely resembled those of normal Type Ib
supernovae (SNe Ib) such as SN 1999ex. This spectroscopic transition defines
Type IIb supernovae, but the strong similarity of SN 2008ax to normal SNe Ib
beginning near maximum light, including an absorption feature near 6270A due to
H-alpha at high velocities, suggests that many objects classified as SNe Ib in
the literature may have ejected similar amounts of hydrogen as SN 2008ax,
roughly a few x 0.01 M_sun. Early-time spectropolarimetry (6 and 9 days after
shock breakout) revealed strong line polarization modulations of 3.4% across
H-alpha, indicating the presence of large asphericities in the outer ejecta.
The continuum shares a common polarization angle with the hydrogen, helium, and
oxygen lines, while the calcium and iron absorptions are oriented at different
angles. This is clear evidence of deviations from axisymmetry even in the outer
ejecta. Intrinsic continuum polarization of 0.64% only nine days after shock
breakout shows that the outer layers of the ejecta were quite aspherical. A
single epoch of late-time spectropolarimetry, as well as the shapes of the
nebular line profiles, demonstrate that asphericities extended from the
outermost layers all the way down to the center of this SN. [Abridged]
01/2010;
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ABSTRACT: We obtained ESI/Keck rotation curves of 10 MgII absorption selected galaxies (0.3 < z < 1.0) for which we have WFPC-2/HST images and high resolution HIRES/Keck and UVES/VLT quasar spectra of the MgII absorption profiles. We perform a kinematic comparison of these galaxies and their associated halo MgII absorption. For all 10 galaxies, the majority of the absorption velocities lie in the range of the observed galaxy rotation velocities. In 7/10 cases, the absorption velocities reside fully to one side of the galaxy systemic velocity and usually align with one arm of the rotation curve. In all cases, a constant rotating thick-disk model poorly reproduces the full spread of observed MgII absorption velocities when reasonably realistic parameters are employed. In 2/10 cases, the galaxy kinematics, star formation surface densities, and absorption kinematics have a resemblance to those of high redshift galaxies showing strong outflows. We find that MgII absorption velocity spread and optical depth distribution may be dependent on galaxy inclination. To further aid in the spatial-kinematic relationships of the data, we apply quasar absorption line techniques to a galaxy (v_c=180 km/s) embedded in LCDM simulations. In the simulations, MgII absorption selects metal enriched "halo" gas out to roughly 100 kpc from the galaxy, tidal streams, filaments, and small satellite galaxies. Within the limitations inherent in the simulations, the majority of the simulated MgII absorption arises in the filaments and tidal streams and is infalling towards the galaxy with velocities between -200 < v_r < -180 km/s. The MgII absorption velocity offset distribution (relative to the simulated galaxy) spans ~200 km/s with the lowest frequency of detecting MgII at the galaxy systematic velocity. Comment: 26 pages, 18 figures, 6 tables. Accepted for publication in the Astrophysical Journal
12/2009;
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ABSTRACT: Molecular transitions recently discovered at redshift zabs=2.059 toward the bright background quasar J2123-0050 are analysed to limit cosmological variation in the proton-to-electron mass ratio, μ ≡ mp/me. Observed with the Keck telescope, the optical spectrum has the highest resolving power and largest number (86) of H2 transitions in such analyses so far. Also, (7) HD transitions are used for the first time to constrain μ-variation. These factors, and an analysis employing the fewest possible free parameters, strongly constrain μ's relative deviation from the current laboratory value: Δμ/μ =(+5.6±5.5stat±2.7sys)×10−6. This is the first Keck result to complement recent constraints from three systems at zabs>2.5 observed with the Very Large Telescope.
Proceedings of the International Astronomical Union 10/2009; 5:321 - 321.
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ABSTRACT: Current theories that seek to unify gravity with the other fundamental interactions suggest that spatial and temporal variation of fundamental constants is a possibility, or even a necessity, in an expanding Universe. Several studies have tried to probe the values of constants at earlier stages in the evolution of the Universe, using tools such as big-bang nucleosynthesis, the Oklo natural nuclear reactor, quasar absorption spectra, and atomic clocks (see, e.g. Flambaum & Berengut (2009)).
Proceedings of the International Astronomical Union 10/2009; 5:304 - 304.
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ABSTRACT: We present the results of three separate searches for HI 21-cm absorption in a total of twelve damped Lyman-alpha absorption systems (DLAs) and sub-DLAs over the redshift range z = 0.86-3.37. We find no absorption in the five systems for which we obtain reasonable sensitivities and add the results to those of other recent surveys in order to investigate factors which could have an effect on the detection rate: We provide evidence that the mix of spin temperature/covering factor ratios seen at low redshift may also exist at high redshift, with a correlation between the 21-cm line strength and the total neutral hydrogen column density, indicating a roughly constant spin temperature/covering factor ratio for all of the DLAs searched. Also, by considering the geometry of a flat expanding Universe together with the projected sizes of the background radio emission regions, we find, for the detections, that the 21-cm line strength is correlated with the size of the absorber. For the non-detections it is apparent that larger absorbers (covering factors) are required in order to exhibit 21-cm absorption, particularly if these DLAs do not arise in spiral galaxies. We also suggest that the recent z = 2.3 detection towards TXS 0311+430 arises in a spiral galaxy, but on the basis of a large absorption cross-section and high metallicity, rather than a low spin temperature Comment: 11 pages, accepted by MNRAS
10/2009;
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[show abstract]
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ABSTRACT: Wavelength calibration in high resolution spectroscopy is a key issue for the delivery of high quality science data. ESO and
MPQ have agreed to develop a wavelength calibration unit demonstrator based on a Laser Frequency Comb, which in comparison
with current standards will significantly improve calibration data. The status and next milestones are summarized.
12/2008: pages 411-413;
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J. Liske,
L. Pasquini,
P. Bonifacio,
F. Bouchy,
R. F. Carswell,
S. Cristiani,
M. Dessauges,
S. D’Odorico,
V. D’Odorico,
A. Grazian, [......], M. T. Murphy,
F. Pepe,
D. Queloz,
R. Rebolo,
S. Udry,
E. Vanzella,
M. Viel,
T. Wiklind,
M. Zapatero,
S. Zucker
[show abstract]
[hide abstract]
ABSTRACT: CODEX and ESPRESSO are concepts for ultra-stable, high-resolution spectrographs at the E-ELT and VLT, respectively. Both instruments
are well motivated by distinct sets of science drivers. However, ESPRESSO will also be a stepping stone towards CODEX both
in a scientific as well as in a technical sense. Here we discuss this role of ESPRESSO with respect to one of the most exciting
CODEX science cases, i.e. the dynamical determination of the cosmic expansion history.
12/2008: pages 243-247;
