Integral Field Spectrographs: a user's view

We easily tend to think of Integral-Field Spectrographs (IFS) along two opposing trends: as either the beautiful combination between photometry and spectroscopy, or as our worst nightmare including the dark side of both worlds. I favour a view where each IFS is considered individually, as one instrument with specific performances which can be used optimally for a certain range of scientific programs. It is indeed true that data-wise, IFS do sometime merge the characteristics of classic (e.g., long-slit) spectrographs with annoying issues associated with Imagers. This is in fact the price to pay to access a drastically different perspective of our favourite targets. The challenge is then to provide the necessary tools to properly handle the corresponding data. However, this should certainly not be thought as something specific to IFS: such a challenge should be accepted for any instrument, and most importantly solved prior to its delivery at the telescope.Comment: 6 pages, 2 figures. Invited talk, to appear in the Proceedings of "The 2007 ESO Instrument Calibration Workshop", ESO Astrophysics Symposia, Springe

Parallel-sequencing of early-type and spiral galaxies

Since Edwin Hubble introduced his famous tuning fork diagram more than 70 years ago, spiral galaxies and early-type galaxies (ETGs) have been regarded as two distinct families. The spirals are characterized by the presence of disks of stars and gas in rapid rotation, while the early-types are gas poor and described as spheroidal systems, with less rotation and often non-axisymmetric shapes. The separation is physically relevant as it implies a distinct path of formation for the two classes of objects. I will give an overview of recent findings, from independent teams, that motivated a radical revision to Hubble's classic view of ETGs. These results imply a much closer link between spiral galaxies and ETGs than generally assumed.Comment: 1 page, 1 figure, LaTeX. Invited talk to the Special Session 3 "Galaxy Evolution Through Secular Processes". To appear in Highlights of Astronomy, Vol. 16, Proc. of the XXVIII IAU General Assembly, Beijing, China, August 2012, ed. T. Montmerle. Cambridge University Pres

Effect of environment on galaxies mass-size distribution: unveiling the transition from outside-in to inside-out evolution

The distribution of galaxies on the mass-size plane as a function of redshift or environment is a powerful test for galaxy formation models. Here we use integral-field stellar kinematics to interpret the variation of the mass-size distribution in two galaxy samples spanning extreme environmental densities. The samples are both identically and nearly mass-selected (stellar mass M*>6e9 Msun) and volume-limited. The first consists of nearby field galaxies from the Atlas3D parent sample. The second consists of galaxies in the Coma Cluster (Abell 1656), one of densest environments for which good resolved spectroscopy can be obtained. The mass-size distribution in the dense environment differs from the field one in two ways: (i) spiral galaxies are replaced by bulge-dominated disk-like fast-rotator early-type galaxies (ETGs), which follow the SAME mass-size relation and have the SAME mass distribution as in the field sample; (ii) the slow rotator ETGs are segregated in mass from the fast rotators, with their size increasing proportionally to their mass. A transition between the two processes appears around the stellar mass M_crit=2e11 Msun. We interpret this as evidence for bulge growth (outside-in evolution) and bulge-related environmental quenching dominating at low masses, with little influence from merging, while significant dry mergers (inside-out evolution) and halo-related quenching driving the mass and size growth at the high-mass end. The existence of these two processes naturally explains the diverse size evolution of galaxies of different masses and the separability of mass and environmental quenching.Comment: 6 pages, 5 figures, LaTeX. Accepted for publication in ApJ Letter

Dynamical masses of early-type galaxies at z~2

The evolution of masses and sizes of passive (early-type) galaxies with redshift provides ideal constraints to galaxy formation models. These parameters can in principle be obtained for large galaxy samples from multi-band photometry alone. However the accuracy of photometric masses is limited by the non-universality of the IMF. Galaxy sizes can be biased at high redshift due to the inferior quality of the imaging data. Both problems can be avoided using galaxy dynamics, and in particular by measuring the galaxies stellar velocity dispersion. Here we provide an overview of the efforts in this direction.Comment: 8 pages, 4 figures, LaTeX. Invited talk to the IAU Symposium 295 "The Intriguing Life of Massive Galaxies". To appear in Proc. of the XXVIII IAU General Assembly, Beijing, China, August 2012, eds. D. Thomas, A. Pasquali & I. Ferreras. Cambridge University Pres

General spherical anisotropic Jeans models of stellar kinematics: including proper motions and radial velocities

Cappellari (2008) presented a flexible and efficient method to model the stellar kinematics of anisotropic axisymmetric and spherical stellar systems. The spherical formalism could be used to model the line-of-sight velocity second moments allowing for essentially arbitrary radial variation in the anisotropy and general luminous and total density profiles. Here we generalize the spherical formalism by providing the expressions for all three components of the projected second moments, including the two proper motion components. A reference implementation is now included in the public JAM package available at http://purl.org/cappellari/softwareComment: 3 pages, 2 figures, LaTeX. Not submitted anywhere but here. Software implementing the update to the JAM method described in this paper is available at http://purl.org/cappellari/softwar