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Register a new userIntegral Field Spectroscopy of two radio galaxies at z~2.3
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Sebastian F. Sanchez
Publication date
2008
fields
Physics
and research's language is
English
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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.
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This study presents Keck optical and infrared spectroscopy of the rest-frame ultraviolet and optical emission lines in two Lyman alpha emitting galaxies at z>2. These data provide insight on the evolution of fundamental galaxy scaling relations at early epochs, especially the luminosity-velocity and luminosity-metallicity relations. Lynx 2-9691 exhibits extended [O III] emission over a diameter of >28 kpc, reminiscent of the Lyman alpha nebulae discovered near Lyman-drop galaxies [Steidel et al 2000]. The ratios of strong nebular emission lines indicate sub-solar oxygen abundances in the range 8.2<12+log(O/H)<8.8 (Z = 0.25-0.95 Z_sun). Interestingly, Galactic metal-rich globular clusters have similar metallicities, consistent with the idea that we could be seeing the formation of galaxies like the Milky Way at $zsim3$. The measured gas phase oxygen abundances are >4-10 times higher than the Z < 0.1 Z_sun metallicities found in damped Lyman alpha (DLA) absorbers at similar redshifts, indicating that DLA systems trace different environments than the vigorously star-forming objects observed here. Star-forming galaxies at $zsim3$ are 2-4 magnitudes more luminous than local spiral galaxies of similar metallicity, and thus, are offset from the local luminosity-metallicity relation. Their kinematic linewidths are sigma_v=65-130 km/s, making this sample 1-3 magnitudes more luminous than local galaxies of similar linewidth and mass. [Abridged]
We present the pilot study component of the Fluorescent Lyman-Alpha Structures in High-z Environments (FLASHES) Survey; the largest integral-field spectroscopy survey to date of the circumgalactic medium at $z=2.3-3.1$. We observed 48 quasar fields between 2015 and 2018 with the Palomar Cosmic Web Imager (Matuszewski et al. 2010). Extended HI Lyman-$mathrm{alpha}$ emission is discovered around 42/48 of the observed quasars, ranging in projected, flux-weighted radius from 21-71 proper kiloparsecs (pkpc), with 26 nebulae exceeding $100mathrm{~pkpc}$ in effective diameter. The circularly averaged surface brightness radial profile peaks at a maximum of $mathrm{1times 10^{-17}~erg~s^{-1}~cm^{-2}~arcsec^{-2}}$ ($2times10^{-15}~mathrm{erg~s^{-1}~cm^{-2}~arcsec^{-2}}$ adjusted for cosmological dimming) and luminosities range from $1.9times10^{43}~mathrm{erg~s^{-1}}$ to $-14.1times10^{43}~mathrm{erg~s^{-1}}$. The emission appears to have a highly eccentric morphology and a maximum covering factor of $50%$ ($60%$ for giant nebulae). On average, the nebular spectra are red-shifted with respect to both the systemic redshift and Ly$alpha$ peak of the quasar spectrum. The integrated spectra of the nebulae mostly have single or double-peaked line shapes with global dispersions ranging from $167~mathrm{km~s^{-1}}$ to $690~mathrm{km~s^{-1}}$, though the individual (Gaussian) components of lines with complex shapes mostly appear to have dispersions $leq 400$ $mathrm{km~s^{-1}}$, and the flux-weighted velocity centroids of the lines vary by thousands of $ mathrm{km~s^{-1}}$ with respect to the systemic QSO redshifts. Finally, the root-mean-square velocities of the nebulae are found to be consistent with gravitational motions expected in dark matter halos of mass $mathrm{M_h simeq10^{12.5} M_odot}$. We compare these results to existing surveys at both higher and lower redshift.
Approximately half of the nearby E+A galaxies followed up with 21-cm observations have detectable HI emission. The optical spectra of these galaxies show strong post-starburst stellar populations but no optical emission lines implying star-formation is not ongoing despite the presence of significant gas reservoirs. We have obtained integral field spectroscopic follow up observations of the two brightest, and nearest, of the six E+A galaxies with HI 21-cm emission in the recent sample of Zwaan et al. (2013). In the central regions of both galaxies the observations are consistent with a post-starburst population with little emission. However, outside the central regions both galaxies have strong optical emission lines, with a clumpy or knot-like distribution, indicating ongoing star-formation. We conclude that in these two cases the presence of optical spectra lacking evidence for star-formation while a large gas mass is present can be explained by an aperture effect in selecting the nearby E+A galaxies using single-fibre spectroscopy that probes only the galaxy core.
We present and analyse integral-field observations of six type-II QSOs with z=0.3-0.4, selected from the Sloan Digital Sky Survey (SDSS). Two of our sample are found to be surrounded by a nebula of warm ionized gas, with the largest nebula extending across 8 (40 kpc). Some regions of the extended nebulae show kinematics that are consistent with gravitational motion, while other regions show relatively perturbed kinematics: velocity shifts and line widths too large to be readily explained by gravitational motion. We propose that a ~20 kpc x20 kpc outflow is present in one of the galaxies. Possible mechanisms for triggering the outflow are discussed. In this object, we also find evidence for ionization both by shocks and the radiation field of the AGN.
We describe a project to study the state of the ISM in ~20 low redshift (z<0.3) QSO host galaxies observed with the PMAS integral field spectrograph. We describe method developement to access the stellar and gas component of the spectrum without the strong nuclear emission to access the host galaxy properties also in the central region. It shows that integral field spectroscopy promises to be very efficient to study the gas distribution and its velocity field, and also spatially resolved stellar population in the host galaxies also of luminous AGN.
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