Evidence for a Supermassive Black Hole in the S0 Galaxy NGC 3245

The S0 galaxy NGC 3245 contains a circumnuclear disk of ionized gas and dust with a radius of 1.1" (110 pc), making it an ideal target for dynamical studies with the Hubble Space Telescope (HST). We have obtained spectra of the nuclear disk with the Space Telescope Imaging Spectrograph, using a 0.2" wide slit at five parallel positions. Measurements of the Hα and [N II] emission lines are used to map out the kinematic structure of the disk in unprecedented detail. The data reveal a rotational velocity field with a steep velocity gradient across the innermost 0.4". We construct dynamical models for a thin gas disk in circular rotation, using HST optical images to map out the gravitational potential due to stars. Our modeling code includes the blurring due to the telescope point-spread function and the nonzero slit width, as well as the instrumental shift in measured wavelength for light entering the slit off-center, so as to simulate the data as closely as possible. The Hα+[N II] surface brightness measured from an HST narrowband image is folded into the models, and we demonstrate that many of the apparent small-scale irregularities in the observed velocity curves are the result of the patchy distribution of emission-line surface brightness. Over most of the disk, the models are able to fit the observed radial velocity curves closely, although there are localized regions within the disk that appear to be kinematically disturbed relative to the overall rotational pattern. The velocity dispersion of [N II] λ6584 rises from σ~50 km/s in the outer disk to ~160 km/s at the nucleus, and most of this line width cannot be attributed to rotational or instrumental broadening. To account for the possible dynamical effect of the intrinsic velocity dispersion in the gas, we also calculate models that include a correction for asymmetric drift. This correction increases the derived black hole mass by 12% but leads to slightly poorer fits to the data. A central dark mass of (2.1+/-0.5)×10^8 Msolar is required for the models to reproduce the steep central velocity gradient. This value for the central mass is consistent with recently discovered correlations between black hole mass and bulge velocity dispersion.Peer reviewe

Constraining reionization using the thermal history of the baryons

The thermal evolution of the intergalactic medium (IGM) depends on the reionization history of the universe. Numerical simulations indicate that the low density IGM, which is responsible for the low column density Ly-alpha forest, follows a well defined temperature-density relation. This results in a cut-off in the distribution of line widths as a function of column density. We use hydrodynamic simulations to calibrate the relation between the cut-off and the temperature-density relation and apply this relation to Keck spectra spanning a redshift range z=2-4.5. We find that the temperature peaks at z~3 and interpret this as evidence for reheating due to the reionization of helium.Comment: 4 pages, 2 figures, to appear in "Cosmic evolution and galaxy formation: Structure, interactions, and feedback", eds. J. Franco et a

The nuclear superbubble of NGC 3079

We have used the Hawaii Imaging Fabry-Perot Interferometer (HIFI) at the CFH 3.6 m telescope to map Hα + [N II] λλ6548, 6583 emission-line profiles across the entire edge-on, nearby SBc galaxy NGC 3079, with resolution 70 km s-1 and subarsecond sampling. Blue and red long-slit spectra were obtained with the Double Spectrograph on the Palomar 5 meter telescope to provide additional emission-line diagnostics. A spectacular, line emitting bubble of diameter 13″ (∼1.1 kpc) is observed immediately east of the nucleus. Its unusual gaseous excitation (e.g., [N II] λ6583/Hα > 1) suggests that shocks are important. Extremely violent gas motions that range over 2000 km s-1 are detected across the bubble and diametrically opposite on the west side of the nucleus. Nonrotational motions are also found in the inner galaxy disk. The complete spatial and spectral sampling of the emission-line profiles allows us to constrain the general flow pattern of the gas in the line-emitting bubble. An ovoidal bubble, inflated from the nucleus with monotonically increasing velocities (V ∝ Rn with 2 < n < 3) and inclined ∼3° from the plane of the sky, provides a good first-order fit to its velocity field. A total ionized mass and kinetic energy of ∼1 × 107/Ne M⊙ and ∼2 × 1056/Ne ergs, respectively, are involved in this outflow. Although the [S II] density in the bubble is only weakly constrained, we find no convincing evidence anywhere in the bubble (even near the nucleus) for the [S II] density to be above the low-density limit (Ne ≈ 125 cm-3). The radial density gradient previously reported in this galaxy is not confirmed, so the [S II] density profile cannot be used to find the size of the energy injection zone in this object. The Balmer decrements in the nucleus and the brighter regions of the outflow show a steep decrease in reddening away from the galaxy plane. The outflow mass is similar to, but the kinetic energy may be 10 times larger than, the superwinds in the Seyfert galaxy NGC 1068 and the starburst galaxy M82. Therefore, the superbubble of NGC 3079 is the most powerful example known of a windblown bubble, and an excellent laboratory to study wind dynamics. The dimensions and energies of the bubble imply that it is likely to be in the blowout phase and partially ruptured. The predicted rate of kinetic energy output from the central starburst appears sufficient to power most of this outflow. It is possible that a central active galactic nucleus also contributes to the outflow

Large-Scale Structure at z~2.5

We have made a statistically complete, unbiased survey of C IV systems toward a region of high QSO density near the South Galactic Pole using 25 lines of sight spanning $1.5<z<2.8$. Such a survey makes an excellent probe of large-scale structure at early epochs. We find evidence for structure on the $15-35h^{-1}$ proper Mpc scale ($H_0 \equiv 100$ km $s^{-1}$ Mpc${-1}$) as determined by the two point C IV - C IV absorber correlation function, and reject the null hypothesis that C IV systems are distributed randomly on such scales at the $\sim 3.5\sigma$ level. The structure likely reflects the distance between two groups of absorbers subtending $\sim~ 13 \times 5 \times 21h^{-3}$ and $\sim 7 \times 1 \times 15h^{-3}$ Mpc$^3$ at $z\sim 2.3$ and $z \sim 2.5$ respectively. There is also a marginal trend for the association of high rest equivalent width C IV absorbers and QSOs at similar redshifts but along different lines of sight. The total number of C IV systems detected is consistent with that which would be expected based on a survey using many widely separated lines of sight. Using the same data, we also find 11 Mg II absorbers in a complete survey toward 24 lines of sight; there is no evidence for Mg II - Mg II or Mg II - QSO clustering, though the sample size is likely still small to detect such structure if it exists.Comment: 56 pages including 32 of figures, in gzip-ed uuencoded postscript format, 1 long table not included, aastex4 package. Accepted for publication in ApJ Supplement

Condensate cosmology -- dark energy from dark matter

Imagine a scenario in which the dark energy forms via the condensation of dark matter at some low redshift. The Compton wavelength therefore changes from small to very large at the transition, unlike quintessence or metamorphosis. We study CMB, large scale structure, supernova and radio galaxy constraints on condensation by performing a 4 parameter likelihood analysis over the Hubble constant and the three parameters associated with Q, the condensate field: Omega_Q, w_f and z_t (energy density and equation of state today, and redshift of transition). Condensation roughly interpolates between Lambda CDM (for large z_t) and sCDM (low z_t) and provides a slightly better fit to the data than Lambda CDM. We confirm that there is no degeneracy in the CMB between H and z_t and discuss the implications of late-time transitions for the Lyman-alpha forest. Finally we discuss the nonlinear phase of both condensation and metamorphosis, which is much more interesting than in standard quintessence models.Comment: 13 pages, 13 colour figures. Final version with discussion of TE cross-correlation spectra for condensation and metamorphosis in light of the WMAP result

The Large Scale Structure in the Universe: From Power-Laws to Acoustic Peaks

The most popular tools for analysing the large scale distribution of galaxies are second-order spatial statistics such as the two-point correlation function or its Fourier transform, the power spectrum. In this review, we explain how our knowledge of cosmic structures, encapsulated by these statistical descriptors, has evolved since their first use when applied on the early galaxy catalogues to the present generation of wide and deep redshift surveys, incorporating the most challenging discovery in the study of the galaxy distribution: the detection of Baryon Acoustic Oscillations.Comment: 20 pages, 12 figures, to appear in "Data Analysis in Cosmology", Lecture Notes in Physics, 2008, eds. V. J. Martinez, E. Saar, E. Martinez-Gonzalez, and M.J. Pons-Borderia, Springer-Verla

QUASAR ABSORPTION LINES. A REVIEW

The paper first reviews the observations of quasar absorption lines, paying particular attention to those objects with multiple redshifts. Recent high-resolution work by Morton and Morton, by Morton and Richstone, by Wingert and by Boksenberg and Sargent has shown that the absorption redshifts frequently are found to split into close pairs or multiples. Boksenberg and Sargent have proposed that this splitting may represent a constant velocity separation between adjacent pairs of redshifts of about 140 km. s-1. Recent observations pertinent to this suggestion are reviewed. The second part of the paper deals with theories concerning the origin of the absorption lines. The existence of the possible magic splitting in redshifts would strongly point to the lines originating in material ejected by the quasar

QUASAR ABSORPTION LINES. A REVIEW

The paper first reviews the observations of quasar absorption lines, paying particular attention to those objects with multiple redshifts. Recent high-resolution work by Morton and Morton, by Morton and Richstone, by Wingert and by Boksenberg and Sargent has shown that the absorption redshifts frequently are found to split into close pairs or multiples. Boksenberg and Sargent have proposed that this splitting may represent a constant velocity separation between adjacent pairs of redshifts of about 140 km. s-1. Recent observations pertinent to this suggestion are reviewed. The second part of the paper deals with theories concerning the origin of the absorption lines. The existence of the possible magic splitting in redshifts would strongly point to the lines originating in material ejected by the quasar

An eruptive BL Lacertae object with a high redshift, 0846 + 51 W1

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe