arXiv subjects

Bruno Milliard

Publications and source records attributed to Bruno Milliard.

58 records · Page 4Linked to original sources

arXiv2004

The Star Formation Rate Function of the Local Universe

We have derived the bivariate luminosity function for the far ultraviolet (1530Angstroms) and far infrared (60 microns). We used matched GALEX and IRAS data, and redshifts from NED and PSC-z. We have derived a total star formation luminosity function phi(L_{tot}), with L_{tot} = L_{FUV}+L_{FIR}. Using these, we determined the cosmic ``star formation rate'' function and density for the local universe. The total SFR function is fit very well by a log-normal distribution over five decades of luminosity. We find that the bivariate luminosity function phi(L_{FUV},L_{FIR}) shows a bimodal behavior, with L_{FIR} tracking L_{FUV} for L_{TOT}< 10^10 L_sun, and L_{FUV} saturating at 10^10 L_sun, while L_{TOT} L_{FIR} for higher luminosities. We also calculate the SFR density and compare it to other measurements.

astro-ph↗

arXiv2004

The Galaxy Evolution Explorer: A Space Ultraviolet Survey Mission

We give an overview of the Galaxy Evolution Explorer (GALEX), a NASA Explorer Mission launched on April 28, 2003. GALEX is performing the first space UV sky-survey, including imaging and grism surveys in two bands (1350-1750 Angstroms and 1750-2750 Angstroms). The surveys include an all-sky imaging survey (m[AB] ~ 20.5), a medium imaging survey of 1000 square degrees (m[AB] ~ 23), a deep imaging survey of 100 square degrees (m[AB] ~ 25), and a nearby galaxy survey. Spectroscopic grism surveys (R=100-200) are underway with various depths and sky coverage. Many targets overlap existing or planned surveys. We will use the measured UV properties of local galaxies, along with corollary observations, to calibrate the UV-global star formation rate relationship in local galaxies. We will apply this calibration to distant galaxies discovered in the deep imaging and spectroscopic surveys to map the history of star formation in the universe over the redshift range 0 < z < 1.5, and probe the physical drivers of star formation in galaxies. The GALEX mission includes a Guest Investigator program supporting the wide variety of programs made possible by the first UV sky survey.

astro-ph↗

arXiv2002

2D analytical modeling of distortion and sky background in multi-fiber spectrographs: the case of the Norris spectrograph at Palomar Mountain

A method for optimal reduction of data taken with multi-fiber spectrographs is described, based on global correction of their geometrical distortion. Though it was specifically developed for reducing observations performed at Palomar Mountain using the Norris fiber spectrograph, this method can be adapted to other types of multi-object spectrographs such as the multi-slit ones. Combined with a 2D analytical interpolation of sky-background that accounts for non-uniform spectral resolution, the Norris software package achieves very high accuracy in airglow subtraction, even in the near infrared (7000-9000A) where molecular band-emissions commonly induce strong artefacts that preclude clean sky subtraction whenever standard image processing techniques are used. Correlatively, an improvement by a factor of 2 on the precision of radial velocities is achievable. Throughout the paper possible improvements to the method are suggested for those devising similar packages for other instruments.

astro-ph↗

arXiv2001

The ultraviolet visibility and quantitative morphology of galactic disks at low and high redshift

We used ultraviolet (200 nm) images of the local spiral galaxies M33, M51, M81, M100, M101 to compute morphological parameters of galactic disks at this wavelength : half-light radius $r_{hl}$, surface brightness distributions, asymmetries ($A$) and concentrations ($C_A$). The visibility and the evolution of the morphological parameters are studied as a function of the redshift. The main results are : local spiral galaxies would be hardly observed and classified if projected at high redshifts (z $\ge$ 1) unless a strong luminosity evolution is assumed. Consequently, the non-detection of large galactic disks cannot be used without caution as a constraint on the evolution of galatic disks. Spiral galaxies observed in ultraviolet appear more irregular since the contribution from the young stellar population becomes predominent. When these galaxies are put in a (log $A$ vs. log $C_A$) diagram, they move to the irregul ar sector defined at visible wavelengths. Moreover, the log $A$ parameter is degenerate and cannot be used for an efficient classification of morphological ultraviolet types. The analysis of high redshift galaxies cannot be carried out in a reliable way so far and a multi-wavelength approach is required if one does not want to misinterpret the data.

astro-ph↗