We present the SINS survey with SINFONI of high redshift galaxies. With 80 objects observed and 63 detected, SINS is the largest survey of spatially resolved gas kinematics, morphologies, and physical properties of star-forming galaxies at z~1-3. We describe the selection of the targets, the observations, and the data reduction. We then focus on the “SINS Halpha sample” of 62 rest-UV/optically-selected sources at 1.3<z<2.6 for which we targeted primarily the Halpha and [NII] emission lines. Only 30% of this sample had previous near-IR spectroscopic observations. As a whole, the SINS Halpha sample covers a reasonable representation of massive log(M*/Msun)>10 star-forming galaxies at z1.5-2.5, with some bias towards bluer systems compared to pure K-selected samples due to the requirement of secure optical redshift. The sample spans two orders of magnitude in stellar mass and in absolute and specific star formation rates, with median values of approximately log(M*/Msun) = 10.5, 70 Msun/
In the now standard model of concordance cosmology, large-scale structure grows through simple gravitational aggregation and collapse from the initial fluctuations in the mass density of the early universe. In this framework, galaxies form as baryonic gas cools at the center of dark matter halos and subsequently grow through accretion and mergers, leading to the hierarchical build-up of galaxy mass. Increasingly deep and wide-area multiwavelength surveys in the past decade have established a fairly robust outline of the global evolution of galaxies over nearly 90% of the age of the universe. Rapid evolution is observed at redshifts z ∼ 1 -4, with the peak of (dust-enshrouded) star formation, luminous QSOs, and major merger activity occurring around z ∼ 2 -3 (e.g., Fan et al. 2001;Chapman et al. 2005;Hopkins & Beacom 2006). By z ∼ 1, roughly half of the stellar mass in galaxies -and > 90% in massive, 10 11 M ⊙ galaxieswas assembled (e.g., Dickinson et al. 2003;Fontana et al. 2003;Rudnick et al. 2003Rudnick et al. , 2006;;Grazian et al. 2007;Conselice et al. 2007).
The epochs around z ∼ 1 -2 also seem to correspond to a crucial transition with the emergence of the bimodality and the Hubble sequence as observed in the present-day galaxy population (e.g., Bell et al. 2004;van den Bergh et al. 1996van den Bergh et al. , 2001;;Lilly et al. 1998;Stanford et al. 2004;Ravindranath et al. 2004;Papovich et al. 2005;Kriek et al. 2008b;Williams et al. 2009).
The details of how galaxies were assembled and evolved remain, however, poorly known. Much of our current knowledge at z 1 still relies heavily on galaxy-integrated spectral energy distributions and colours, and on global properties such as stellar mass and age, star formation rate, interstellar extinction, and sizes. Studies based on integrated spectroscopy (mostly in the optical, much fewer in the infrared and submillimeter) are still comparatively scarce but have provided secure redshifts for various photometricallyselected samples, and first results notably on galactic-scale outflows, dynamical masses, gas mass fractions, and nebular abundances. More direct and detailed constraints are however needed to understand the formation and evolution of galaxies, involving angular momentum exchange and loss, cooling, dissipation, dynamical processes, and feedback from star formation and active galactic nuclei (AGN). Such constraints are crucial as input and benchmarks for theories and simulations of galaxy formation and evolution.
Of particular relevance in this context is the issue of the dominant mechanisms by which massive galaxies at high redshift assemble their baryonic mass, and what processes drive their star formation activity and early evolution. While major merging is undoubtedly taking place at high redshift (e.g., Tacconi et al. 2006Tacconi et al. , 2008)), new observational results suggest that rapid but more continuous gas accretion via “cold flows” and/or minor mergers likely played an important role in driving star formation and mass growth of the massive star-forming galaxy population at z 1 (e.g., Noeske et al. 2007;Elbaz et al. 2007;Daddi et al. 2007). This is in line with recent theoretical work based on both semi-analytical approaches and hydrodynamical simulations (e.g., Keres et al. 2005;Dekel & Birnboim 2006;Kitzbichler & White 2007;Naab et al. 2007;Guo & White 2008;Davé 2008;Genel et al. 2008;Dekel et al. 2009a). The results from our own SINFONI survey of kinematics of z ∼ 2 galaxies (the subject of the present paper), as well as similar studies carried out by other teams (e.g., Erb et al. 2003Erb et al. , 2006b;;Law et al. 2007bLaw et al. , 2009;;Wright et al. 2007Wright et al. , 2009) ) have provided key evidence in support of this alternative scenario, at least in a significant number of the galaxies observed.
This emphasizes the crucial role of spatially-and spectrally-resolved investigations of individual galaxies at early stages of their evolution. Such studies enable the mapping of kinematics and morphologies, and of the distribution of star formation, gas and stars, and physical properties such as chemical abundances and excitation state of the gas. The constraints and results can then be fed into studies of larger samples (connecting through global galaxy parameters such as mass and star formation rate), and theoretical models and numerical simulations (as observationally motivated ingredients and assumptions). Obtaining spatially-/spectrally-resolved data is however notoriously challenging because of the faintness of high redshift galaxies, and also because many important spectral diagnostic features are redshifted out of the optical bands. The advent of sensitive nearinfrared (near-IR) integral field spectrometers mounted on 8 -10 m class ground-based telescopes have recently opened up this avenue (e.g. Förster Schreiber et al. 2006a;Genzel et al. 2006;Nesvadba et al. 2006aNesvadba et al. ,b, 2007Nesvadba et al. , 2008;;Swinbank et
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