arXiv subjects

Martin Giard

Publications and source records attributed to Martin Giard.

13 recordsLinked to original sources

arXiv2023

Environmental transition: overview of actions to reduce the environmental footprint of astronomy

To keep current global warming below 1.5{\deg}C compared with the pre-industrial era, measures must be taken as quickly as possible in all spheres of society. Astronomy must also make its contribution. In this proceeding, and during the workshop to which it refers, different levers of actions are discussed through various examples: individual efforts, laboratory-level actions, impact evaluation and mitigation in major projects, institutional level, and involvement through collectives.

astro-ph.IM↗

arXiv2019

Investigation of the Origin of the Anomalous Microwave Emission in Lambda Orionis

The anomalous microwave emission (AME) still lacks a conclusive explanation. This excess of emission, roughly between 10 and 50 GHz, tends to defy attempts to explain it as synchrotron or free-free emission. The overlap with frequencies important for cosmic microwave background explorations, combined with a strong correlation with interstellar dust, drive cross-disciplinary collaboration between interstellar medium and observational cosmology. The apparent relationship with dust has prompted a ``spinning dust'' hypothesis. The typical peak frequency range of the AME profile implicates spinning grains on the order of 1 nm. This points to polycyclic aromatic hydrocarbons (PAHs). We use data from the AKARI/Infrared Camera (IRC), due to its thorough PAH-band coverage, to compare AME from the Planck Collaboration astrophysical component separation product with infrared dust emission in the Orionis AME-prominent region. We look also at infrared dust emission from other mid IR and far-IR bands. The results and discussion contained here apply to an angular scale of approximately 1{\deg}. We find that certainly dust mass correlates with AME, and that PAH-related emission in the AKARI/IRC 9 {\mu}m band correlates slightly more strongly. Using hierarchical Bayesian inference and full dust spectral energy distribution (SED) modeling we argue that AME in {\lambda}Orionis correlates more strongly with PAH mass than with total dust mass, lending support for a spinning PAH hypothesis within this region. We emphasize that future efforts to understand AME should focus on individual regions, and a detailed comparison of the PAH features with the variation of the AME SED.

astro-ph.GA↗

arXiv2018

QUBIC: Exploring the primordial Universe with the Q\&U Bolometric Interferometer

In this paper we describe QUBIC, an experiment that will observe the polarized microwave sky with a novel approach, which combines the sensitivity of state-of-the art bolometric detectors with the systematic effects control typical of interferometers. QUBIC unique features are the so-called "self-calibration", a technique that allows us to clean the measured data from instrumental effects, and its spectral imaging power, i.e. the ability to separate the signal in various sub-bands within each frequency band. QUBIC will observe the sky in two main frequency bands: 150 GHz and 220 GHz. A technological demonstrator is currently under testing and will be deployed in Argentina during 2019, while the final instrument is expected to be installed during 2020.

astro-ph.IM↗

arXiv2018

Using ALMA to resolve the nature of the early star-forming large-scale structure PLCK G073.4-57.5

Galaxy clusters at high redshift are key targets for understanding matter assembly in the early Universe, yet they are challenging to locate. A sample of >2000 high-z candidate structures has been found using Planck's all-sky submm maps, and a sub-set of 234 have been followed up with Herschel-SPIRE, which showed that the emission can be attributed to large overdensities of dusty star-forming galaxies. In order to resolve and characterise the individual galaxies we targeted the eight brightest SPIRE sources in the centre of the Planck peak PLCK G073.4-57.5 using ALMA at 1.3 mm, and complemented these observations with data from IRAC, WIRCam J,K, and SCUBA-2. We detected a total of 18 millimetre galaxies brighter than 0.3 mJy in 2.4 arcmin^2. The ALMA source density is 8-30 times higher than average background estimates and larger than seen in typical 'proto-cluster' fields. We were able to match all but one of the ALMA sources to a NIR counterpart. The most significant (four) SCUBA-2 sources are not included in the ALMA pointings, but we find an 8sigma stacking detection of the ALMA sources in the SCUBA-2 map at 850 um. We derive photo-z, L_IR, SFR, stellar mass, T_dust, M_dust for all of the ALMA galaxies; the photo-zs identify two groups each of five sources, at z~1.5 and 2.4. The two groups show two 'red sequences' (i.e. similar NIR [3.6]-[4.5] colours and different J-K colours). The majority of the ALMA-detected galaxies are on the SFR versus stellar mass main sequence, and half of the sample is more massive than the characteristic stellar mass at the corresponding redshift. Serendipitous CO line detections in two of the galaxies appear to match their photometric redshifts at z~1.54. We performed an analysis of star-formation efficiencies and CO- and mm-continuum-derived gas fractions of our ALMA sources, combined with a sample of 1<z<3 cluster and proto-cluster members.

astro-ph.GA↗

arXiv2018

A look at possible microwave dust emission via AKARI infrared all-sky surveys

The anomalous microwave emission (AME) still lacks a conclusive explanation. This excess of emission, roughly between 10 and 50 GHz, correlates spatially with interstellar dust, prompting a "spinning dust" hypothesis: electric dipole emission by rapidly rotating, small dust grains. The typical peak frequency range of the AME profile implicates grains on the order of ~1 nm, suggesting polycyclic aromatic hydrocarbon molecules (PAHs). We compare AKARI/Infrared Camera (IRC), with its thorough PAH-band coverage, to AME intensity estimates from the Planck Collaboration, in the λ Orionis region. We look also at infrared dust emission from other mid IR and far-IR bands. The results and discussion contained here apply to an angular scale of approximately 1°. In general, our results support an AME-from-dust hypothesis. In λ Orionis, we find that certainly dust mass correlates with AME, and that PAH-related emission in the AKARI/IRC 9 μm band may correlate slightly more strongly.

astro-ph.GA↗

arXiv2018

Searching for the Culprit of Anomalous Microwave Emission: An AKARI PAH-range Analysis of Probable Electric Dipole Emitting Regions

In the evolutionary path of interstellar medium inquiry, many new species of interstellar dust have been modeled and discovered. The modes by which these species interact and evolve are beginning to be understood, but in recent years a peculiar new feature has appeared in microwave surveys. Anomalous microwave emission (AME), appearing between 10 and 90 GHz, has been correlated with thermal dust emission, leading to the popular suggestion that this anomaly is electric dipole emission from spinning dust. The observed frequencies suggest that spinning grains should be on the order of 1 nm in size, hinting at poly-cyclic aromatic hydrocarbon molecules. We present data from AKARI/Infrared Camera (IRC), due to the effective PAH/Unidentified Infrared Band (UIR) coverage of its 9 micron survey to investigate their role within a few regions showing strong AME in the Planck low frequency data. We include the well studied Perseus and rho Ophiuchi clouds . We use the IRAS/IRIS 100 micron data to account for the overall dust temperature. We present our results as abundance maps for dust emitting around 9 micron, and 100 micron. Part of the AME in these regions may actually be attributed to thermal dust emission, or the star forming nature of these targets is masking the vibrational modes of PAHs which should be present there, suggesting further investigation for various galactic environments.

astro-ph.GA↗

arXiv2014

PRISM (Polarized Radiation Imaging and Spectroscopy Mission): An Extended White Paper

PRISM (Polarized Radiation Imaging and Spectroscopy Mission) was proposed to ESA in May 2013 as a large-class mission for investigating within the framework of the ESA Cosmic Vision program a set of important scientific questions that require high resolution, high sensitivity, full-sky observations of the sky emission at wavelengths ranging from millimeter-wave to the far-infrared. PRISM's main objective is to explore the distant universe, probing cosmic history from very early times until now as well as the structures, distribution of matter, and velocity flows throughout our Hubble volume. PRISM will survey the full sky in a large number of frequency bands in both intensity and polarization and will measure the absolute spectrum of sky emission more than three orders of magnitude better than COBE FIRAS. The aim of this Extended White Paper is to provide a more detailed overview of the highlights of the new science that will be made possible by PRISM

astro-ph.CO↗

arXiv2010

Statistical investigation of the non-thermal emission of galaxy clusters

A diffuse non-thermal component has now been observed in massive merging clusters. To better characterise this component, and to extend analyses done for massive clusters down to a lower mass regime, we are conducting a statistical analysis over a large number of X-ray clusters (from ROSAT based catalogues). By means of their stacked radio and X-ray emissions, we are investigating correlations between the non-thermal and the thermal baryonic components. We will present preliminary results on radio-X scaling relations with which we aim to probe the mechanisms that power diffuse radio emission ; to better constrain whether the non-thermal cluster properties are compatible with a hierarchical framework of structure formation ; and to quantify the non-thermal pressure.

astro-ph.CO↗

arXiv2009

L1506: a prestellar core in the making

Exploring the structure and dynamics of cold starless clouds is necessary to understand the different steps leading to the formation of protostars. Because clouds evolve slowly, many of them must be studied in detail to pick up different moments of a cloud's lifetime. We study here L1506C in the Taurus region, a core with interesting dust properties which have been evidenced with the PRONAOS balloon-borne telescope. To trace the mass content of L1506C and its kinematics, we mapped the dust emission, and the line emission of two key species, C18O and N2H+ (plus 13CO and C17O). This cloud shows peculiar features: i) a large envelope traced solely by 13CO holding a much smaller core with a strong C18O depletion in its center despite a low maximum opacity (Av~20 mag), ii) extremely narrow C18O lines indicating a low, non-measurable turbulence, iii) contraction traced by C18O itself (plus rotation), iv) unexpectedly, the kinematical signature from the external envelope is opposite to the core one: the 13CO and C18O velocity gradients have opposite directions and opposite profiles (C18O blue peaked, 13CO red peaked). The core is large (r = 3E4 AU) and not very dense (n(H2) ? 5E4 cm-3 or less). This core is therefore not prestellar yet. All these facts suggest that the core is kinematically detached from its envelope and in the process of forming a prestellar core. This is the first time that the dynamical formation of a prestellar core is witnessed. The extremely low turbulence could be the reason for the strong depletion of this core despite its relatively low density and opacity in contrast with undepleted cores such as L1521E which shows a turbulence at least 4 times as high.

astro-ph.GA↗

arXiv2008

The Infrared Luminosity of Galaxy Clusters

The aim of this study is to quantify the infrared luminosity of clusters as a function of redshift and compare this with the X-ray luminosity. This can potentially constrain the origin of the infrared emission to be intracluster dust and/or dust heated by star formation in the cluster galaxies. We perform a statistical analysis of a large sample of galaxy clusters selected from existing databases and catalogues.We coadd the infrared IRAS and X-ray RASS images in the direction of the selected clusters within successive redshift intervals up to z = 1. We find that the total infrared luminosity is very high and on average 20 times higher than the X-ray luminosity. If all the infrared luminosity is to be attributed to emission from diffuse intracluster dust, then the IR to X-ray ratio implies a dust-to-gas mass abundance of 5e-4. However, the infrared luminosity shows a strong enhancement for 0.1 < z < 1, which cannot be attributed to cluster selection effects. We show that this enhancement is compatible with a star formation rate in the member galaxies that is typical of the central Mpc of the Coma cluster at z = 0 and evolves with the redshift as (1+z)^5. It is likely that most of the infrared luminosity that we measure is generated by the ongoing star formation in the member galaxies. From theoretical predictions calibrated on extinction measurements (dust mass abundance equal to 1e-5), we expect only a minor contribution, of a few percent, from intracluster dust.

astro-ph↗

arXiv2008

The impact of dust on the scaling properties of galaxy clusters

We investigate the effect of dust on the scaling properties of galaxy clusters based on hydrodynamic N-body simulations of structure formation. We have simulated five dust models plus a radiative cooling and adiabatic models using the same initial conditions for all runs. The numerical implementation of dust was based on the analytical computations of Montier and Giard (2004). We set up dust simulations to cover different combinations of dust parameters that put in evidence the effects of size and abundance of dust grains. Comparing our radiative plus dust cooling runs to a purely radiative cooling simulation we find that dust has an impact on cluster scaling relations. It mainly affects the normalisation of the scalings (and their evolution), whereas it introduces no significant differences on their slopes. The strength of the effect depends critically on the dust abundance and grain size parameters as well as on the cluster scaling. Indeed, cooling due to dust is effective at the cluster regime and has a stronger effect on the "baryon driven" statistical properties of clusters such as $L_{\rm X}-M$, $Y- M$, $S-M$ scaling relations. Major differences, relative to the radiative cooling model, are as high as 25% for the $L_{\rm X}-M$ normalisation, and about 10% for the $Y-M$ and $S-M$ normalisations at redshift zero. On the other hand, we find that dust has almost no impact on the "dark matter driven" $T_{\rm mw}-M$ scaling relation. The effects are found to be dependent in equal parts on both dust abundances and grain sizes distributions for the scalings investigated in this paper. Higher dust abundances and smaller grain sizes cause larger departures from the radiative cooling (i.e. with no dust) model.

astro-ph↗

arXiv2001

Map-making methods for Cosmic Microwave Background experiments

The map-making step of Cosmic Microwave Background data analysis involves linear inversion problems which cannot be performed by a brute force approach for the large timelines of today. We present in this article optimal vector-only map-making methods, which are an iterative COBE method, a Wiener direct filter and a Wiener iterative method. We apply these methods on diverse simulated data, and we show that they produce very well restored maps, by removing nearly completely the correlated noise which appears as intense stripes on the simply pixel-averaged maps. The COBE iterative method can be applied to any signals, assuming the stationarity of the noise in the timeline. The Wiener methods assume both the stationarity of the noise and the sky, which is the case for CMB-only data. We apply the methods to Galactic signals too, and test them on balloon-borne experiment strategies and on a satellite whole sky survey.

astro-ph↗

arXiv2001

How to make CMB maps from huge timelines with small computers

We present in this article two different ways to make CMB maps in practice, from large timelines. One is to make a simple destriping, fitting the data and using the scan intercepts to remove the low frequency noise (stripes). The second, optimal, is to resolve linearly the map-making problem, which in case of big timelines must be simplified and changed from matrices to vectors for the calculations. Assuming few conditions on the noise, it is possible to make fast map-making tools.

astro-ph↗