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Register a new userSINFONI Integral Field Spectroscopy of z~2 UV-selected Galaxies: Rotation Curves and Dynamical Evolution
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Added by
Natascha M. F\\\"orster Schreiber
Publication date
2006
fields
Physics
and research's language is
English
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We present 0.5 resolution near-IR integral field spectroscopy of the Ha line emission of 14 z~2 UV-selected BM/BX galaxies obtained with SINFONI at ESO/VLT. The mean Ha half-light radius r_1/2 is about 4kpc and line emission is detected over > ~20kpc in several sources. In 9 sources, we detect spatially-resolved velocity gradients, from 40 to 410 km/s over ~10kpc. The observed kinematics of the larger systems are consistent with orbital motions. Four galaxies are well described by rotating disks with clumpy morphologies and we extract rotation curves out to radii > ~10kpc. One or two galaxies exhibit signatures more consistent with mergers. Analyzing all 14 galaxies in the framework of rotating disks, we infer mean inclination- and beam-corrected maximum circular velocities v_c of 180+-90 km/s and dynamical masses of (0.5-25)x10^10 Msun within r_1/2. On average, the dynamical masses are consistent with photometric stellar masses assuming a Chabrier/Kroupa IMF but too small for a 0.1-100 Msun Salpeter IMF. The specific angular momenta of our BM/BX galaxies are similar to those of local late-type galaxies. The specific angular momenta of their baryons are comparable to those of their dark matter halos. Extrapolating from the average v_c at 10kpc, the virial mass of the typical halo of a galaxy in our sample is 10^(11.7+-0.5) Msun. Kinematic modeling of the 3 best cases implies a ratio of v_c to local velocity dispersion of order 2-4 and accordingly a large geometric thickness. We argue that this suggests a mass accretion (alternatively, gas exhaustion) timescale of ~500Myr. We also argue that if our BM/BX galaxies were initially gas rich, their clumpy disks will subsequently lose their angular momentum and form compact bulges on a timescale of ~1 Gyr. [ABRIDGED]
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We present the results of H- and K-band VLT/SINFONI integral field spectroscopy of the ULIRG IRAS 19254-7245 (The Super-antennae), an interacting double galaxy system containing an embedded AGN. Deep K-band spectroscopy reveals PaAlpha arising in a warped disc with position angle of 330 degree and an inclination i=40-55 degree. The kinemetric parameters derived for H2 are similar to PaAlpha. Two high-ionization emission lines, [SiVI] and [AlIX], are detected and we identify as [NiII] the line observed at 1.94 micron. Diluting non-stellar continuum, which was previously detected, has decayed, and the H-band continuum emission is consistent with pure stellar emission. Based on H2 emission line ratios it is likely that at the central 1-kpc region H2 is excited by UV fluorescence in dense clouds while shock excitation is dominant further out. This scenario is supported by very low PaAlpha to H2 line ratio detected outside the nuclear region and non-thermal ortho/para ratios (~2.0 - 2.5) close to the nucleus.
In this article we study the morphology, kinematics and ionization properties of the giant ionized gas nebulae surrounding two high redshift radio galaxies, 4C40.36 (z=2.27) and 4C48.48 (z=2.34).}{Integral Field Spectroscopy observations were taken using the PPAK bundle of the PMAS spectrograph, mounted on the 3.5m on the Calar Alto Observatory, in order to cover a field-of-view of 64 X 72 centered in each radio galaxy. The observations spanned over 5 nights, using two different spectral resolutions (with FWHM~4 AA and ~8 AA respectively), covering the optical wavelength range from ~3700 AA to ~7100 AA, which corresponds to the rest-frame ultraviolet range from ~1100 AA to ~2000 AA >. Various emission lines are detected within this wavelength range, including Lyalpha (1216 AA), NV (1240 AA), CIV (1549 AA), HeII (1640 AA), OIII] (1663 AA) and CIII] (1909AA). The dataset was used to derive the spatial distribution of the flux intensity of each of these lines and the gas kinematics. The properties of the emission lines in the nuclear regions were studied in detail.In agreement with previous studies, we find that both objects are embedded in a large ionized gas nebula, where Ly alpha emission is extended across ~100 kpc or more. The CIV and HeII emission lines are also spatially extended. The nebulae are generally aligned with the radio axis, although we detect emission far from it. In 4C+48.48, there is a band of low Ly-alpha/CIV running perpendicular to the radio axis, at the location of the active nucleus. This feature might be the observational signature of an edge-on disk of neutral gas. The kinematics of both nebulae are inconsistent with stable rotation, although they are not inconsistent with infall or outflow.
We study the properties of galaxies at z=2 in a Lambda CDM universe, using two different types of hydrodynamic simulation methods (Eulerian TVD and SPH) and a spectrophotometric analysis in the Un, G, R filter set. The simulated galaxies at z=2 satisfy the color-selection criteria proposed by Adelberger et al. (2004) when we assume Calzetti extinction with E(B-V)=0.15. We find that the number density of simulated galaxies brighter than R<25.5 at z=2 is about 2e-2 h^3/Mpc^3, roughly one order of magnitude larger than that of Lyman break galaxies at z=3. The most massive galaxies at z=2 have stellar masses >~1e11 Msun, and their observed-frame G-R colors lie in the range 0.0<G-R<1.0. They typically have been continuously forming stars with a rate exceeding 30 Msun/yr over a few Gyrs from z=10 to z=2, although the TVD simulation indicates a more sporadic star formation history than the SPH simulations. Of order half of their stellar mass was already assembled by z~4. The reddest massive galaxies at z=2 with G-R >= 1.0 and Mstar>1e10 Msun/h finished the build-up of their stellar mass by z~3. Interestingly, our study suggests that the majority of the most massive galaxies at z=2 should be detectable at rest-frame UV wavelengths, contrary to some recent claims made on the basis of near-IR studies of galaxies at the same epoch, provided the median extinction is less than E(B-V)<0.3. However, our results also suggest that the fraction of stellar mass contained in galaxies that pass the color-selection criteria could be as low as 50% of the total stellar mass in the Universe at z=2. Our simulations suggest that the missing stellar mass is contained in fainter (R>25.5) and intrinsically redder galaxies. Our results do not suggest that hierarchical galaxy formation fails to account for the massive galaxies at z>=1. (abridged)
We present an analysis of the H2 emission-line gas kinematics in the inner < 4 arcsec radius of six nearby spiral galaxies, based on AO-assisted integral-field observations obtained in the K-band with SINFONI/VLT. Four of the six galaxies in our sample display ordered H2 velocity fields, consistent with gas moving in the plane of the galaxy and rotating in the same direction as the stars. However, the gas kinematics is typically far from simple circular motion. We can classify the observed velocity fields into four different types of flows, ordered by increasing complexity: (1) circular motion in a disc (NGC3351); (2) oval motion in the galaxy plane (NGC3627 and NGC4536); (3) streaming motion superimposed on circular rotation (NGC4501); and (4) disordered streaming motions (NGC4569 and NGC4579). The H2 velocity dispersion in the galaxies is usually higher than 50 km/s in the inner 1-2 arcsec radii. The four galaxies with ordered kinematics have v/sigma < 1 at radii less than 40-80 pc. The radius at which v/sigma = 1 is independent of the type of nuclear activity. While the low values of v/sigma could be taken as an indication of a thick disc in the innermost regions of the galaxies, other lines of evidence (e.g. H2 morphologies and velocity fields) argue for a thin disc interpretation in the case of NGC3351 and NGC4536. We discuss the implications of the high values of velocity dispersion for the dynamics of the gaseous disc and suggest caution when interpreting the velocity dispersion of ionized and warm tracers as being entirely dynamical. Understanding the nature and role of the velocity dispersion in the gas dynamics, together with the full 2D information of the gas, is essential for obtaining accurate black hole masses from gas kinematics.
We use a new stacking technique to obtain mean mid IR and far IR to far UV flux ratios over the rest near-UV/near-IR color-magnitude diagram. We employ COMBO-17 redshifts and COMBO-17 optical, GALEX far and near UV, Spitzer IRAC and MIPS Mid IR photometry. This technique permits us to probe infrared excess (IRX), the ratio of far IR to far UV luminosity, and specific star formation rate (SSFR) and their co-evolution over two orders of magnitude of stellar mass and redshift 0.1<z<1.2. We find that the SSFR and the characteristic mass (M_0) above which the SSFR drops increase with redshift (downsizing). At any given epoch, IRX is an increasing function of mass up to M_0. Above this mass IRX falls, suggesting gas exhaustion. In a given mass bin below M_0 IRX increases with time in a fashion consistent with enrichment. We interpret these trends using a simple model with a Schmidt-Kennicutt law and extinction that tracks gas density and enrichment. We find that the average IRX and SSFR follows a galaxy age parameter which is determined mainly by the galaxy mass and time since formation. We conclude that blue sequence galaxies have properties which show simple, systematic trends with mass and time such as the steady build-up of heavy elements in the interstellar media of evolving galaxies and the exhaustion of gas in galaxies that are evolving off the blue sequence. The IRX represents a tool for selecting galaxies at various stages of evolution.
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