.. Time-stamp: <2022-02-21 12:30:40 ycopin>
Science
=======
Mission spatiale de cosmologie observationnelle EUCLID
------------------------------------------------------
.. image:: http://www.mpia.de/1910892/standard.jpg
:alt: Near-Infrared Spectro-Photometer
:width: 200 px
:align: right
**Euclid** est une mission spatiale de l':abbr:`ESA (Agence Spatiale
Européenne)` destinée à étudier, via diverses sondes cosmologiques
(cisaillement gravitationnel, oscillations acoustiques de baryons, etc.), le
contenu sombre – énergie et matière noires – de l'Univers, et dont le décollage
est prévu pour mi 2023.
Je participe au `Euclid Consortium `_ depuis 2012,
essentiellement dans le domaine du traitement et de l'analyse des données en
provenance du spectrographie sans fente `NISP
`_, et en tant que responsable
scientifique à l'IP2I; plus spécifiquement:
* *Co-lead* de l'activité de réduction des données de spectrographie sans fente
(PF-SIR),
* *Deputy calibration scientist*, en charge de la spectroscopie.
.. image:: _static/images/EUC_SIM_NISRGS000-25424-1_20210521T082656.195Z_SC8_MAIN_EUCLID_657_1_512px.png
:alt: NISP simulated exposure.
:width: 400 px
:align: center
:target: _static/images/EUC_SIM_NISRGS000-25424-1_20210521T082656.195Z_SC8_MAIN_EUCLID_657_1_DET13.SCI.png
.. rubric:: Liens
* `EUCL-IPN-TN-8-001 <_static/documents/EUCL-IPN-TN-8-001.pdf>`_
*Impact of spectral covariance on line fitting*
I look for the impact of the spectral covariance on the line fitting
procedure. It appears that the maximum-likelihood estimates — for
all line parameters — are equally *un*-biased when using the correct
full-covariance χ² definition and the simpler pure-diagonal one
(i.e. neglecting spectral correlations). However, best-fit parameter
uncertainties — on line flux, position/*redshift* and width — are
systematically *under*-estimated by ~40% when using the
uncorrelated χ², while properly estimated when minimizing the
statistically correct χ². The use of spectral covariance is
therefore of crucial importance to derive statistically controlled
spectral quantities such as redshift and line fluxes.
* `EUCL-IPN-TN-8-002 <_static/documents/EUCL-IPN-TN-8-002.pdf>`_
*Adaptive Emission Line Detection*
To derive spectral quantities such as redshift, the first step in
the process of precision emission line adjustment in a galaxy
spectrum is to detect potential emission lines in a robust and
systematic way. I present in this note a collection of algorithms
developed for that purpose, including optimal spectrum combination,
adaptive fitting and robust M-estimators.
* `EUCL-IPN-TN-8-003 <_static/documents/EUCL-IPN-TN-8-003.pdf>`_
*Outlier detection in small samples using pull-clipping*
We present and tests different algorithms to compute the mean of very small
samples (*n = 4*) in presence of a small fraction of outliers. The favorite
choice appears to be the inverse-variance weighted mean of pull-clipped
values, both more robust and statistically efficient (from 10% to 40%) than
the median.
* `Grism-based Spectrograph Modeling
`_
This module implements the spectrograph optical model used for the
SuperNova Integral Field Spectrograph Lantz04_ data-reduction
pipeline, and presented in Copin00_. It provides a flexible
chromatic mapping between the input focal plane and the output
detector plane, based on an effective simplified ray-tracing model
of the key optical elements defining the spectrograph (collimator,
prism, grating, camera), described by a restricted number of
physically-motivated distortion parameters.
.. _Lantz04: http://adsabs.harvard.edu/abs/2004SPIE.5249..146L
.. _Copin00: https://tel.archives-ouvertes.fr/tel-00001338/fr/
* `Euclid Spectroscopy Analysis Software `_
This code addresses the different modules in SGS-SPE PE-5300 *Spectral
Features Measurement*.
Modélisation directe de la spectrographie sans fente
----------------------------------------------------
Je développe dans le cadre de l'expérience Euclid une expertise sur la
modélisation directe (*forward modeling*) de la spectrographie sans fente,
parfois appelée imagerie dispersée.
Cinématique des galaxies
''''''''''''''''''''''''
* `Forward modeling of galaxy kinematics in slitless spectroscopy
`_ (Outini & Copin,
2020, A&A **633**, 43O)
Slitless spectroscopy has long been considered as a complicated and
confused technique. Nonetheless, with the advent of Hubble Space Telescope
(HST) instruments characterized by a low sky background level and a high
spatial resolution (most notably WFC3), slitless spectroscopy has become an
adopted survey tool to study galaxy evolution from space. We investigate
its application to single object studies to measure not only redshift and
integrated spectral features, but also spatially resolved quantities such
as galaxy kinematics. We build a complete forward model to be
quantitatively compared to actual slitless observations. This model depends
on a simplified thin cold disk galaxy description -- including flux
distribution, intrinsic spectrum and kinematic parameters -- and on the
instrumental signature. It is used to improve redshifts and constrain basic
rotation curve parameters, i.e. plateau velocity v0 (in km/s) and central
velocity gradient w0 (in km/s/arcsec). The model is tested on selected
observations from 3D-HST and GLASS surveys, to estimate redshift and
kinematic parameters on several galaxies measured with one or more roll
angles. Our forward approach allows to mitigate the self-contamination
effect, a primary drawback of slitless spectroscopy, and therefore has the
potential to increase precision on redshifts. In a limited sample of
well-resolved spiral galaxies from HST surveys, it is possible to
significantly constrain galaxy rotation curve parameters. This
proof-of-concept work is promising for future large slitless spectroscopic
surveys such as EUCLID and WFIRST.
* `Presentation `_ at the `The Art of
Measuring Galaxy Physical Properties `_
conference |en|
* `Mesure de la cinématique interne des galaxies en spectroscopie sans fente
`_, thèse de M. Outini |fr|
Caractérisation atmosphérique LSST
''''''''''''''''''''''''''''''''''
Je travaille, en collaboration avec Jérémy Neveu et al., sur l'utilisation de
la spectrographie sans fente pour la caractérisation de la transmission
atmosphérique pour LSST.
Spectro-photométrie des supernovæ de type Ia
--------------------------------------------
.. image:: _static/images/logo_SNfactory.png
:alt: Design Dianna LaFerry
:width: 200 px
:align: right
Les supernovæ thermonucléaires (dites de type Ia) sont des chandelles
standard à portée cosmologique, et ont permis la découverte de
l'expansion accélérée de l'Univers (`prix Nobel de physique 2011
`_)
Depuis sa création en 2001, je suis impliqué dans le projet international
`Nearby SuperNova Factory `_ de suivi
spectro-photométrique de SNe Ia proches, où je suis *data scientist*,
responsable du traitement des données du *SuperNova Integral Field
Spectrograph*.
* `SNfactory presentation <_static/documents/SNf-Berlin15.pdf>`_
(2015/03, Humboldt University, Berlin, |en|)
* `LBNL news releases
`_
* `Publication list `_
.. raw:: html
Spectrographie à champ intégral
-------------------------------
Mon expertise instrumentale est la *spectrographie à champ intégral*
(`integral-field spectrography
`_),
parfois appelée *spectrographie 3D*.
* A `3D-spectroscopy course <_static/documents/IFSC2015_IFS_YCopin.pdf>`_ I
gave at the *Indo-French Astronomy School for Optical Spectroscopy* (2015/11,
Pune, |en|).
* 3D-specific tools: `Adaptive Voronoi binning
`_ (`code IDL/python
`_),
`kinemetry `_
(`code IDL `_)
Galaxies de type précoce
------------------------
J'ai longtemps été impliqué dans le projet `SAURON
`_, dont l'objectif principal
est l'étude des mécanismes de formation et d'évolution des galaxies de
type précoce à partir d'observations 3D sur un spectrographe à champ
panoramique dédié.
.. |fr| image:: _static/images/france_flag_icon.png
:alt: Fr
.. |en| image:: _static/images/uk_flag_icon.png
:alt: En