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Since 2010, the main focus of my research has been the COLD GASS survey, a census of molecular gas in a large, unbiased sample of local massive galaxies. The molecular gas data, obtained at the IRAM 30m telescope, is complemented by a rich multi-wavelength dataset, from Arecibo 21cm spectra to GALEX images. Details about the project, the main results, and the list of publications can be found on the COLD GASS website.



The Arecibo Legacy Fast ALFA Survey (ALFALFA) is a major ongoing project at the Arecibo Observatory. When completed, it will have covered 7000 square degrees and at least 25,000 galaxies will have been detected. My thesis work was based in large part on data from this survey.

My technical contributions to the project are:

  • observing : I am part of the ALFALFA observing team that works on gathering all the data. In 2005, we were scheduled on about 200 nights! I am also part of the ALFALFA optical follow-up team, and as such have done some optical spectroscopy of interesting dwarf galaxies discovered in the survey and coordinated some of the optical imaging effort.
  • data processing : A lot of data means a lot of data reduction. Everybody pitches in. All the data reduction is done with "home-made" IDL-based software.
  • software development : My main contribution to LOVEDATA, the data processing package for ALFALFA, is a series of programs to automatically identify galaxies at various stages in the data reduction pipeline (more on this below).

(my ALFALFA science projects are described farther down).

Related publications:

  • The Arecibo Legacy Fast ALFA Survey: V. HI Source Catalog of the Anti-Virgo Region at 27 degrees
    A. Saintonge, R. Giovanelli, M.P. Haynes, G.L. Hoffman, B.R. Kent, A.M. Martin & S.Stierwalt
    2008, AJ, 135, 588
    |ADS |astro-ph|
  • Optically Inert HI Detections toward the Virgo Cluster detected in the Arecibo Legacy Fast ALFA Survey
    B.R. Kent, R. Giovanelli, M.P. Haynes, A. Saintonge, S.Stierwalt, T. Balonek, B. Catinella, R.A. Koopmann, E. Momjian & K. Spekkens
    2007, ApJL, 665, 15
    |ADS |astro-ph|
  • The Arecibo Legacy Fast ALFA Survey: IV. Strategies for Signal Identification and Survey Catalog Reliability
    A. Saintonge
    2007, AJ, 133, 2087
    |ADS |astro-ph|
  • The Arecibo Legacy Fast ALFA Survey: III. HI Source Catalog of the Northern Virgo Cluster Region
    R. Giovanelli, M.P. Haynes, B.R. Kent, A. Saintonge, S. Stierwalt (+17 coauthors)
    2007, AJ, 133, 2569
    |ADS |astro-ph|
  • The Arecibo Legacy Fast ALFA Survey: II. Results of Precursor Observations
    R. Giovanelli, M.P. Haynes, B.R. Kent, P. Perillat, B. Catinella, G.L. Hoffman, E. Momjian, J.L. Rosenverg, A. Saintonge, K. Spekkens (+10 coauthors),
    2005, AJ, 130, 2613
    |ADS| astro-ph|
  • The Arecibo Legacy Fast ALFA Survey: I. Science Goals, Survey Design, and Strategy
    R. Giovanelli, M.P. Haynes, B.R. Kent, P. Perillat, A. Saintonge, N. Brosch, B. Catinella, G.L. Hoffman, S. Stierwalt, K. Spekkens (+30 coauthors),
    2005, AJ, 130, 2598
    |ADS |astro-ph|

Dwarf Galaxy

Dwarf Galaxies

My thesis work focused on the diverse properties of dwarf galaxies, from the processes leading to the onset of star formation, to the environmental dependencies of their chemical content and their distribution in the cosmic density field. The project capitalized on the strengths of the ALFALFA survey: its ability to detect very low mass dwarf galaxies based on their gas contents, giving us access to an interesting and otherwise difficult to study population of objects, nearby gas-rich galaxies that have extremely low optical surface brightnesses, and generally very low metallicities. The specific questions that I addressed are:

  • star formation histories: by combining the ALFALFA HI 21cm data with broad-band optical imaging, narrow-band Halpha imaging and optical spectroscopy, we can get a complete picture of the star formation history of this interesting class of galaxies. How old are the stellar populations?, What can we say about the conditions required to lead to the onset of star formation?
  • metallicity vs environment: if the low-mass, very metal-poor galaxies discovered by ALFALFA represent a population of "young" galaxies, then their gas is almost pristine and can trace the gas composition at the time they collapsed. If this is the case, is there global difference in the metallicity of such objects found in clusters with those found in voids?
  • cosmic distribution of dwarfs: is there such a thing as a "void phenomenon"? (i.e. an absence of low mass galaxies in regions of space that are also devoid of massive galaxies) Theory predics low mass galaxies should be more uniformly distributed, yet this is not observed, though it is not know if this is because they are in fact non-existent or because they have not been detected yet. With it's unprecedented sensitivity for low HI mass galaxies in a blind survey, ALFALFA may be able to shed some light on this problem

Related publications:

  • The Arecibo Legacy Fast ALFA Survey: The a.40 HI Source Catalog, its Characteristics and their Impact on the Derivation of the HI Mass Function
    M.P. Haynes, R. Giovanelli, A.M. Martin, K.M. Hess, A. Saintonge, E.A. Adams, G. Hallenbect & 17 co-authors
    2011, AJ, 142, 170
    |ADS |astro-ph|
  • The Survey of HI in Extremely Low-mass Dwarfs (SHIELD)
    J.M Cannon, R. Giovanelli, M.P. Haynes, S. Janowiecki, A. Parker + 13 co-authors including A. Saintonge
    2011, ApJL, 739, 22
    |ADS |astro-ph|
  • The Arecibo Legacy Fast ALFA Survey: V. HI Source Catalog of the Anti-Virgo Region at 27 degrees
    A. Saintonge, R. Giovanelli, M.P. Haynes, G.L. Hoffman, B.R. Kent, A.M. Martin & S.Stierwalt
    2008, AJ, 135, 588
    |ADS |astro-ph|

Hubble Ultra Deep Field

High Redshift Galaxies

My interests also extend much farther out in space. At MPE, I am involved in the PEP survey, a Herschel guaranteed time survey of some of the most popular extragalactic deep fields (GOODS, COSMOS, EGS,...). In particular, I am conducting follow-up observations to investigate the dust and gas properties of high redshift galaxies. Previously, I also conducted research on galaxies at intermediate and high redshifts while at Cornell, at the Herzberg Institute of Astrophysics (HIA), and in Zurich, mostly focussing on the role of environment in galaxy evolution. Here is a brief description of these various projects:

  • PACS Evolutionary Probe (PEP)
    Visit the website of the PEP survey for all the results, access to the data, and an up-to-date list of publications.
    As a follow-up of the PEP observations in GOODS-N, I obtained IRAM PdBI CO spectra and studied with B. Magnelli and the MPE/PEP team the molecular gas contents of z~1 star-forming galaxies, using dust masses derived from Herschel photometry to derive empirical prescriptions for the CO-to-H2 conversion factor. The results of this study are published in this paper.

  • Spitzer Mid-Infrared Cluster Survey (SMIRCS)
    In collaboration with Vy Tran, I have been looking at Spitzer mid-infrared imaging of galaxy clusters. The mid-infrared observations reveal dusty star formation, hidden at optical wavelengths. We have a sample of 8 clusters for which large spectroscopic catalogs and HST imaging are available. The combination of all these outstanding datasets allows us to study the evolution of the star-formation properties of galaxies in clusters through time, and across different environments (field vs groups vs clusters). In the first paper of our study, we show that the fraction of dusty star-forming cluster members increases significantly with redshift, from 3% at z=0.02 to 13% at z=0.83 (for galaxies with star formation rates larger than 5 solar masses per year). We also have strong evidence suggesting that this increase is due to the process of cluster assembly, with galaxies undergoing the dusty starbursts as they enter the clusters. For a general overview of these results, also have a look at this news feature from Spitzer.

  • Geometrical Tests of Cosmological Models using the Kinematics of High-redshift Galaxies
    In this project, we performed some classical geometrical tests (angular diameter-redshift relation and Hubble diagram) to put constraints on important cosmological parameters. These tests are done by identifying a set of standard rods/candles and tracing their observable properties (anglar size, magnitude, number density) through redshift. What is new in this project is the way in which the standard rods were selected: by using the scaling relations between the rotation velocity of a disc galaxy and its physical diameter and absolute luminosity. We perform the test on the first data products of the Vimos/VLT Deep Survey (VVDS), which provided data at z=0.2-1. By assuming a reasonable model for the luminosity evolution of large rotating discs, we can exclude both a flat matter-dominated cosmology and an open cosmology with no dark energy contribution. Inversely, by assuming a standard cosmology, we can gain considerable insights about the size and luminosity evolution of disc galaxies.

  • Galaxy Morphology in Rich Clusters
    This research was done while I was an undergraduate at the Université de Montréal and doing research at HIA. Using software developed by David Schade to obtain quantitative information about the morphology of galaxies, I studied the population of galaxies in several rich clusters of galaxies. My main project consisted of studying four clusters spanning the redshift range 0.3-0.8 to study the evolution of galaxies in the extreme cluster environment. I proposed a new way of normalizing the number counts of galaxies in each cluster in order to be able to directly compare the various observations. Using this technique, I calculated the luminosity evolution of disc galaxies in clusters by studying the relation between disc scale length and surface brightness.

Related publications:

  • For an up-to-date list, see the ADS listing
  • A Spectroscopically Confirmed Excess of 24 micron Sources in a Super Galaxy Group at z=0.37: Enhanced Dusty Star Formation Relative to the Cluster and Field Environment
    K-V H. Tran, A. Saintonge, J. Moustakas, L. Bai, A.H. Gonzalez, B.P. Holden, D. Zaritsky & S.J. Kautsch
    2009, ApJ, 705, 809
    |ADS |astro-ph|
  • Spitzer/MIPS Observations of Galaxy Clusters: An Increasing Fraction of Obscured Star-forming Members from z=0.02 to z=0.83
    A. Saintonge, K-V H. Tran & B.P. Holden
    2008, ApJL, 685, 113
    |ADS |astro-ph|
  • Geometrical Tests of Cosmological Models: I. Probing Dark Energy Using the Kinematics of High Redshift Galaxies
    C. Marinoni, A. Saintonge, O. Le Fèvre, A. Mazure, R. Giovanelli & M.P. Haynes
    2008, A&A, 478, 43
    |ADS |astro-ph|
  • Geometrical Tests of Cosmological Models: II. Calibration of Rotational Widths and the Tully-Fisher Relation
    A. Saintonge, K.L. Masters, S. Spekkens, C. Marinoni, R. Giovanelli & M.P. Haynes
    2008, A&A, 478, 57
    |ADS |astro-ph|
  • Geometrical Tests of Cosmological Models: III. The Cosmology-Evolution Diagram at z=1
    C. Marinoni, A. Saintonge, T. Contini, R. Giovanelli, S. Gwyn, M.P. Haynes, O. Ilbert, V. Le Brun, O. Le Fèvre, K.L. Masters, A. Mazure, P. Taxil, L. Tresse & J.M. Virey
    2008, A&A, 478, 71
    |ADS |astro-ph|
  • Catalog of Galaxy Morphology in Four Rich Clusters: Luminosity Evolution of Disk Galaxies at 0.33<z<0.83
    A. Saintonge, D. Schade, E. Ellingson, H.K.C. Yee & R.G. Carlberg
    2005, AJ, 130, 2598
    |ADS |astro-ph|
  • Galaxy Morphology in the Rich Cluster Abell 2390
    J.B. Hutchings, A. Saintonge, D. Schade & D. Frenette
    2002, AJ, 123, 1826
    |ADS |astro-ph|

Signal Extraction

Signal Extraction

The ALFALFA survey will detect tens of thousands of galaxies, spread over millions of spectra. Obviously, there is a strong need for an automated way to detect these galaxies. My algorithm is based on the convolution of template "galaxies" with the spectra. It works by convolving each spectrum with a set of templates of varying widths and finding the best match. By virtue of the convolution theorem, all of this is done in Fourier space which makes the search timewise efficient. From the value of the convolution at the position where it is maximized, it is possible to fully determine the parameters of the best-fit model. A detection signal-to-noise threshold is then applied to reject detections that are likely false. This threshold is established by studying the reliability of the Extractor when applied on a sample of simulated galaxies.

The search is done in Fourier space one spectrum at the time. The detections made in individual spectra are then associated and modeled in the two spatial direction, to get a full three dimensional parametrisation of the galaxy candidate detections. Two versions of the program exist: the first let's us do a preliminary search for galaxies when individual declination strips of our survey area are observed and the second is used to produce the survey catalogs when the observations of any area of the sky are completed.

Related publications:

  • The Arecibo Legacy Fast ALFA Survey. IV. Strategies for Signal Identification and Survey Catalog Reliability
    A. Saintonge
    2007, AJ, 133, 2087
    |ADS |astro-ph|

Related abstracts:

  • A Signal Extraction Utility for the ALFALFA Survey
    A. Saintonge, R. Giovanelli, M.P. Haynes, B.R. Kent, S. Stierwalt, N. Brosch, B. Catinella & E. Momjian
    2005, Bulletin of the American Astronomical Society, 37, 1480