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fbtwitterlinkedinvimeoflicker grey 14rssslideshare1

Galaxy formation and femtosecond frequency combs

Title
Galaxy formation and femtosecond frequency combs
Funding
ARC | Discovery Projects
Contract (GA) number
DP0877998
Start Date
2008/01/01
End Date
2012/12/31
Open Access mandate
no
Organizations
-
More information
http://purl.org/au-research/grants/arc/DP0877998

 

  • Constraint on a variation of the proton-to-electron mass ratio from H2 absorption towards quasar Q2348-011

    Bagdonaite, J.; Murphy, M.T.; Kaper, L.; Ubachs, W. (2012)
    Projects: ARC | Galaxy formation and femtosecond frequency combs (DP0877998)
    Molecular hydrogen (H2) absorption features observed in the line-of-sight to Q2348-011 at redshift zabs = 2.426 are analysed for the purpose of detecting a possible variation of the proton-to-electron mass ratio mu=mp/me. By its structure Q2348-011 is the most complex analysed H2 absorption system at high redshift so far, featuring at least seven distinctly visible molecular velocity components. The multiple velocity components associated with each transition of H2 were modeled simultaneously...

    Revisiting the origin of the high metallicities of sub-damped Lyman-alpha systems

    Dessauges-Zavadsky, Miroslava; Ellison, Sara L.; Murphy, Michael T. (2009)
    Projects: ARC | Galaxy formation and femtosecond frequency combs (DP0877998)
    Sub-damped Lyman-alpha systems (sub-DLAs) have previously been found to exhibit a steeper metallicity evolution than the classical damped Lyman-alpha systems (DLAs), evolving to close to solar metallicity by z~1. From new high-resolution spectra of 17 sub-DLAs we have increased the number of measurements of [Fe/H] at z

    Laser frequency combs for astronomical observations

    Steinmetz, Tilo; Wilken, Tobias; Araujo-Hauck, Constanza; Holzwarth, Ronald; Hänsch, Theodor W.; Pasquini, Luca; Manescau, Antonio; D'Odorico, Sandro; Murphy, Michael T.; Kentischer, Thomas; Schmidt, Wolfgang; Udem, Thomas (2008)
    Projects: ARC | Galaxy formation and femtosecond frequency combs (DP0877998)
    A direct measurement of the universe's expansion history could be made by observing in real time the evolution of the cosmological redshift of distant objects. However, this would require measurements of Doppler velocity drifts of about 1 centimeter per second per year, and astronomical spectrographs have not yet been calibrated to this tolerance. We demonstrate the first use of a laser frequency comb for wavelength calibration of an astronomical telescope. Even with a simple analysis, absolu...

    Redshifted HI and OH absorption in radio galaxies and quasars

    Curran, S. J.; Whiting, M. T.; Murphy, M. T.; Webb, J. K.; Bignell, C.; Polatidis, A. G.; Wiklind, T.; Francis, P.; Langston, G. (2010)
    Projects: ARC | Galaxy formation and femtosecond frequency combs (DP0877998)
    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 b...

    New constraint on cosmological variation of the proton-to-electron mass ratio from Q0528-250

    King, Julian A.; Murphy, Michael T.; Ubachs, Wim; Webb, John K. (2011)
    Projects: ARC | Galaxy formation and femtosecond frequency combs (DP0877998)
    Molecular hydrogen transitions in quasar spectra can be used to constrain variation in the proton-to-electron mass ratio, $\mu\equiv m_p/m_e$, at high redshifts ($z\gtrsim 2$). We present here an analysis of a new spectrum of the quasar Q0528$-$250, obtained on VLT/UVES (the Ultraviolet and Visual Echelle Spectrograph, on the Very Large Telescope), and analyse the well-known H$_2$ absorber at $z=2.811$ in this spectrum. For the first time we detect HD (deuterated molecular hydrogen) in this s...

    New searches for HI 21-cm in damped Lyman-alpha absorption systems

    Curran, S. J.; Tzanavaris, P.; Darling, J. K.; Whiting, M. T.; Bignell, J. K. Webb C.; Athreya, R.; Murphy, M. T. (2009)
    Projects: ARC | Galaxy formation and femtosecond frequency combs (DP0877998)
    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...

    An absorption-selected survey of neutral gas in the Milky Way halo

    Bekhti, N. Ben; Winkel, B.; Richter, P.; Kerp, J.; Klein, U.; Murphy, M. T. (2012)
    Projects: ARC | Galaxy formation and femtosecond frequency combs (DP0877998)
    We aim at analysing systematically the distribution and physical properties of neutral and mildly ionised gas in the Milky Way halo, based on a large absorption-selected data set. Multi-wavelength studies were performed combining optical absorption line data of CaII and NaI with follow-up HI 21-cm emission line observations along 408 sight lines towards low- and high-redshift QSOs. We made use of archival optical spectra obtained with UVES/VLT. HI data were extracted from the Effelsberg-Bonn ...

    The density, the cosmic microwave background and the proton-to-electron mass ratio in a cloud at redshift 0.9

    Henkel, C.; Menten, K. M.; Murphy, M. T.; Jethava, N.; Flambaum, V. V.; Braatz, J. A.; Muller, S.; Ott, J.; Mao, R. Q. (2009)
    Projects: ARC | Galaxy formation and femtosecond frequency combs (DP0877998)
    Based on measurements with the Effelsberg 100-m telescope, a multi-line study of molecular species is presented toward the gravitational lens system PKS 1830–211, which is by far the best known target to study dense cool gas in absorption at intermediate redshift. Determining average radial velocities and performing Large Velocity Gradient radiative transfer calculations, the aims of this study are (1) to determine the density of the gas, (2) to constrain the temperature of the cosmic microw...

    Deuterium Abundance in the Most Metal-Poor Damped Lyman alpha System: Converging on Omega_baryons

    Pettini, Max; Zych, Berkeley J.; Murphy, Michael T.; Lewis, Antony; Steidel, Charles C. (2008)
    Projects: ARC | Galaxy formation and femtosecond frequency combs (DP0877998)
    The most metal-poor DLA known to date, at z = 2.61843 in the spectrum of the QSO Q0913+072, with an oxygen abundance only about 1/250 of the solar value, shows six well resolved D I Lyman series transitions in high quality echelle spectra recently obtained with the ESO VLT. We deduce a value of the deuterium abundance log (D/H) = -4.56+/-0.04 which is in good agreement with four out of the six most reliable previous determinations of this ratio in QSO absorbers. We find plausible reasons why ...

    Keck constraints on a varying fine-structure constant: wavelength calibration errors

    Murphy, Michael T.; Webb, John K.; Flambaum, Victor V. (2009)
    Projects: ARC | Galaxy formation and femtosecond frequency combs (DP0877998)
    The Keck telescope's HIRES spectrograph has previously provided evidence for a smaller fine-structure constant, alpha, compared to the current laboratory value, in a sample of 143 quasar absorption systems: da/a=(-0.57+/-0.11)x10^{-5}. This was based on a variety of metal-ion transitions which, if alpha varies, experience different relative velocity shifts. This result is yet to be robustly contradicted, or confirmed, by measurements on other telescopes and spectrographs; it remains crucial t...
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