My research is focused on cosmology and the study of the cosmic microwave background (CMB). I use measurements of the CMB to improve our knowledge and understanding of models of the early universe like inflation, and to study in detail the initial density perturbations of the universe that have seeded structure formation. I'm interested the physics of galactic emission mechanisms at radio and millimetre wavelengths, in multi-frequency component separation methods and algorithm development, in the impact and mitigation of the effect of systematics on CMB polarization measurements, and in survey design of CMB experiments.
CV: [pdf]
Teaching:
- Introduction to Scientific Programming [pdf]
- Introduction to inflation [lecture]
PACT meetings: Together with Bobby Acharya (ICTP) and Francesco Longo (U. Trieste) I am co-organiser of the "Particles, Astrophysics, Cosmology, Trieste"
(PACT) meetings, which are planned to be regular series of meetings
approximately twice yearly for physicists in the Trieste region. For
more information about PACT, please visit the PACT website.
Experimental collaborations:
| - Planck - a European satellite mission (launched May 14 2009) with the goal to make the definitive all-sky maps of the CMB temperature variations. The goal is to establish the cosmological parameters, such as baryon and dark matter density, and to make a map of the initial fluctuations that lead to structure formation. For an overview of the status of Planck (circa December 2009) please download this talk that I prepared for the PACT1 meeting (Particles, Astrophysics, Cosmology, Trieste). |  |
| - EBEX - a long duration balloon flight mission that will make a 400 square degree deep map of the CMB polarization variations. The goal is to detect the "B-mode" polarization, in order to understand better the mechanism that actually produced the dominant scalar perturbations. To learn more please have a read of our recent SPIE conference proceedings by Reichborn-Kjennerud et al 2010. To browse a few of my photos from the Fort Sumner test flight campaign (April-June 2009), please click here. |  |
Outreach:
- To watch a WorldWideTelescope tour (in Italian) on the subject of dark matter and galaxy clusters, prepared with Jason Dick, please click here : [avi] [wtt (requires Microsoft WWT software)].
Research environment: Looking for research fellowships ? For what aims to be a comprehensive listing of astronomy fellowships in Europe, read this [article]
Ongoing analysis projects
Miramare - A maximum likelihood parametric component
separation method. This
technique solves the data model, d=As+n, where d is
multi-frequency data, A is the mixing matrix (containing free
parameters which may be estimated at the map level), s are the
components (estimated pixel by pixel) and n is noise. Potential
applications include CMB B-mode polarization and the
Sunyaev-Zel'dovich effect from clusters.
Find out more: [The paper]
[The conference talk] [Application to B-mode detection]
Hexsky - A scanning strategy simulator for balloon-borne CMB experiments. This code is used as part of mission planning and simulation for the EBEX experiment. Documention is available [here].
Collaborators: Chaoyun Bao (U. Minnesota), Will Grainger (Cardiff), Nicolas Ponthieu (IAS, Paris), Radek Stompor (APC, Paris).
Contact details
Samuel
Leach
Astrophysics
Sector
International School for Advanced Studies
(SISSA)
via Bonomea 265
34136 Trieste
Italy.
Fifth floor - office 512
leach at sissa.it
Tel: +39-040-3787527
Fax: +39-040-3787528
Selected and recent papers
"Maximum likelihood, parametric component separation and CMB B-mode detection in suborbital experiments"
- Federico Stivoli, Julien Grain, S.M.L., M. Tristram, C. Baccigalupi, R. Stompor
- MNRAS accepted [abstract]
"Single-field inflation constraints from CMB and SDSS data"
- Fabio Finelli, Jan Hamann, S.M.L, Julien Lesgourgues
- JCAP04(2010)011 [Abstract]
"Modelling the galactic magnetic field on the plane in 2D"
- Tess Jaffe, J. Patrick Leahy, Anthony Banday, S.M.L, Stuart Lowe, Althea Wilkinson
- MNRAS, 401:2, 1013-1028 (2009) [Abstract]
"Maximum Likelihood parametric component separation algorithm for CMB experiments"
- Radek Stompor, S.M.L, Federico Stivoli, Carlo Baccigalupi
- MNRAS, 392, 216 (2009) [Abstract]
"Component separation methods for the Planck mission
"
- S.M.L, Jean-Francois Cardoso et al
- Astron.Astrophys.491:597-615 (2008) [Abstract]
"WMAP 3yr data with the CCA: anomalous emission and impact of component separation on the CMB power spectrum"
- Anna Bonaldi, Sara Ricciardi, S.M.L, Federico. Stivoli, Carlo Baccigalupi, Gianfranco De Zotti
- MNRAS, Vol. 382 Issue 4, P 1791 - 1803 (2007) [Abstract]
"The
WMAP normalization of inflationary cosmologies"
- Andrew R Liddle, David Parkinson, S.M.L., Pia Mukherjee
- Phys.Rev. D74 (2006) 083512 [Abstract]
"Measuring
the
primordial power spectrum: Principal component analysis of the cosmic
microwave background"
- S.M.L.
- Mon.Not.Roy.Astron.Soc. 372 (2006) 646-654 [Abstract]
[PhyStat'05 proceedings]
"Structure formation constraints
on the
Jordan-Brans-Dicke theory"
- Viviana Acquaviva, Carlo Baccigalupi, S.M.L., Andrew R.
Liddle,
Francesca Perrotta
- Phys.Rev. D71 (2005) 104025. [Abstract]
"Constraining slow-roll inflation with WMAP and 2dF"
- S.M.L., Andrew R. Liddle
- Phys.Rev. D68 (2003) 123508. [Abstract]
[Inflation module]
"How long before the end of inflation were observable
perturbations
produced?"
- Andrew R. Liddle, S.M.L.
- Phys.Rev. D68 (2003) 12350. [Abstract]
"Cosmological parameter determination and the inflationary cosmology"
- S.M.L., Andrew R. Liddle, Jerome Martin, Dominic Schwarz
- Phys.Rev. D66 (2002) 023515. [Abstract]
"Enhancement of superhorizon scale inflationary curvature
perturbations"
- S.M.L., Misao Sasaki, David Wands, Andrew R. Liddle
- Phys.Rev. D64 (2001) 023512. [Abstract]