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Quasar outflows have long been recognized as potential contributors to the co-evolution between supermassive black holes (SMBHs) and their host galaxies. The role of outflows in AGN feedback processes can be better understood by placing observational constraints on wind locations and kinetic energies. We utilize broad absorption line (BAL) variability to investigate the properties of a sample of 71 BAL quasars with P$\thinspace$V broad absorption. The presence of P$\thinspace$V BALs indicates that other BALs like C$\thinspace$IV are saturated, such that variability in those lines favours clouds crossing the line of sight. We use these constraints with measurements of BAL variability to estimate outflow locations and energetics. Our data set consists of multiple-epoch spectra from the Sloan Digital Sky Survey and MDM Observatory. We detect significant (4$��$) BAL variations from 10 quasars in our sample over rest frame time-scales between < 0.2-3.8 yr. Our derived distances for the 10 variable outflows are nominally < 1-10 pc from the SMBH using the transverse-motion scenario, and < 100-1000 pc from the central source using ionization-change considerations. These distances, in combination with the estimated high outflow column densities (i.e. $N_{\textrm{H}}$ > 10$^{22}$ cm$^{-2}$), yield outflow kinetic luminosities between ~ 0.001-1 times the bolometric luminosity of the quasar, indicating that many absorber energies within our sample are viable for AGN feedback., 19 pages, 3 figures, 4 tables, 1 supplementary figure, accepted to MNRAS

Quasar outflows have been posited as a mechanism to couple super-massive black holes to evolution in their host galaxies. We use multi-epoch spectra from the Hubble Space Telescope and ground-based observatories to study the outflows in seven quasars that have CIV outflow lines ranging from a classic BAL to weaker/narrower "mini-BALs" across rest wavelengths of at least 850 $\AA$ to 1650 $\AA$. The CIV outflow lines all varied within a time frame of $\leq$ 1.9 yrs (rest). This includes equal occurrences of strengthening and weakening plus the emergence of a new BAL system at $-$38,800 km/s accompanied by dramatic strengthening in a mini-BAL at $-$22,800 km/s. We infer from $\sim$1:1 doublet ratios in PV and other lines that the BAL system is highly saturated with line-of-sight covering fractions ranging from 0.27 to 0.80 in the highest to lowest column density regions, respectively. Three of the mini-BALs also provide evidence for saturation and partial covering based on $\sim$1:1 doublet ratios. We speculate that the BALs and mini-BALs form in similar clumpy/filamentary outflows, with mini-BALs identifying smaller or fewer clumps along our lines of sight. If we attribute the line variabilities to clumps crossing our lines of sight at roughly Keplerian speeds, then a typical variability time in our study, $\sim$1.1 yrs, corresponds to a distance $\sim$2 pc from the central black hole. Combining this with the speed and minimum total column density inferred from the PV BAL, $N_H \gtrsim$ 2.5$\times$10$^{22}$ cm$^{-2}$, suggests that the BAL outflow kinetic energy is in the range believed to be sufficient for feedback to galaxy evolution., Comment: 20 pages, 5 figures, accepted to MNRAS for publication

The majority of low-ionization nuclear emission-line regions (LINERs) harbor supermassive black holes with very low accretion rates. However, the accretion flows do not produce enough ionizing photons to power the emission lines emitted on scales of ~100 pc, and therefore additional sources of power are required. We present and analyze Hubble Space Telescope spectra of three nearby luminous LINERs that are spatially resolved on scales of < 9 pc. The targets have multiple indicators of an accreting black hole, as well as a deficient ionizing photon budget. We measure diagnostic emission line ratios as a function of distance from the nucleus and compare them to models for different excitation mechanisms: shocks, photoionization by the accreting black hole, and photoionization by young or old hot stars. We also consider the kinematics of the line-emitting gas, as revealed by the widths and shifts of the emission lines. We conclude that, in LINERs with low-luminosity active nuclei, shocks by jets or other outflows are crucial in exciting the gas in and around the nucleus, as suggested by other authors. The physical model that best describes our targets comprises a low-luminosity, accretion-powered active nucleus that photoionizes the gas within ~20 pc of the galaxy center, and shock excitation of the gas at larger distances., Accepted to ApJ on 23 July 2018

FeLoBALs are a rare class of quasar outflows with low-ionization broad absorption lines (BALs), large column densities, and potentially large kinetic energies that might be important for `feedback' to galaxy evolution. In order to probe the physical properties of these outflows, we conducted a multiple-epoch, absorption line variability study of 12 FeLoBAL quasars spanning a redshift range between 0.7 and 1.9 over rest frame time-scales of approximately 10 d to 7.6 yr. We detect absorption line variability with greater than 8 sigma confidence in 3 out of the 12 sources in our sample over time-scales of 0.6 to 7.6 yr. Variable wavelength intervals are associated with ground and excited state Fe II multiplets, the Mg II 2796, 2803 doublet, Mg I 2852, and excited state Ni II multiplets. The observed variability along with evidence of saturation in the absorption lines favors transverse motions of gas across the line of sight (LOS) as the preferred scenario, and allows us to constrain the outflow distance from the supermassive black hole (SMBH) to be less than 69, 7, and 60 pc for our three variable sources. In combination with other studies, these results suggest that the outflowing gas in FeLoBAL quasars resides on a range of scales and includes matter within tens of parsecs of the central source., Comment: 21 pages, 6 figures, 2 supplementary figures (attached at the end of the manuscript), accepted to Monthly Notices of the Royal Astronomical Society

Following our study on the incidence, morphology and kinematics of the ionised gas in early-type galaxies we now address the question of what is powering the observed nebular emission. To constrain the likely sources of gas excitation, we resort to a variety of ancillary data, draw from complementary information on the gas kinematics, stellar populations and galactic potential from the SAURON data, and use the SAURON-specific diagnostic diagram juxtaposing the [OIII]/Hb and [NI]/Hb line ratios. We find a tight correlation between the stellar surface brightness and the flux of the Hb recombination line across our sample, which points to a diffuse and old stellar source as the main contributor of ionising photons in early-type galaxies, with post-asymptotic giant branch (pAGB) stars being still the best candidate based on ionising-balance arguments. Other ionising sources such as a central AGN, OB-stars, shocks or the interaction between the hot and warm phases of the interestellar medium are found to play only a limited or localised role in powering the diffuse nebular emission observed in our sample galaxies. These results lead us to investigate the relative importance of stellar and AGN photoionisation in explaining the ionised-gas emission observed in early-type galaxies by the Sloan Digital Sky Survey (SDSS). By simulating how our sample galaxies would appear if placed at further distance and targeted by the SDSS, we conclude that only in very few, if any, of the SDSS early-type galaxies that display modest values for the equivalent width of the [OIII] line (less than ~2.4\AA) and LINER-like [OIII]/Hb values, the nebular emission is truly powered by an AGN., Comment: Accepted for publication in MNRAS. 24 pages, 17 figures. A version with full resolution figures is available at http://star-www.herts.ac.uk/~sarzi/Publications/Sarzi_09_SauronXVI.pdf

In this first paper in a series we present 1298 low-redshift (z\leq0.2) optical spectra of 582 Type Ia supernovae (SNe Ia) observed from 1989 through 2008 as part of the Berkeley SN Ia Program (BSNIP). 584 spectra of 199 SNe Ia have well-calibrated light curves with measured distance moduli, and many of the spectra have been corrected for host-galaxy contamination. Most of the data were obtained using the Kast double spectrograph mounted on the Shane 3 m telescope at Lick Observatory and have a typical wavelength range of 3300-10,400 Ang., roughly twice as wide as spectra from most previously published datasets. We present our observing and reduction procedures, and we describe the resulting SN Database (SNDB), which will be an online, public, searchable database containing all of our fully reduced spectra and companion photometry. In addition, we discuss our spectral classification scheme (using the SuperNova IDentification code, SNID; Blondin & Tonry 2007), utilising our newly constructed set of SNID spectral templates. These templates allow us to accurately classify our entire dataset, and by doing so we are able to reclassify a handful of objects as bona fide SNe Ia and a few other objects as members of some of the peculiar SN Ia subtypes. In fact, our dataset includes spectra of nearly 90 spectroscopically peculiar SNe Ia. We also present spectroscopic host-galaxy redshifts of some SNe Ia where these values were previously unknown. [Abridged]

Broad absorption lines (BALs) in quasar spectra indicate high-velocity outflows that may be present in all quasars and could be an important contributor to feedback to their host galaxies. Variability studies of BALs help illuminate the structure, evolution and basic physical properties of the outflows. Here we present further results from an ongoing BAL monitoring campaign of a sample of 24 luminous quasars at redshifts 1.2 −20 000 km s^(−1), 47 per cent of quasars exhibited Si iv variability while 31 per cent exhibited C iv variability. Furthermore, ∼50 per cent of the variable Si iv regions did not have corresponding C iv variability at the same velocities, while nearly all occurrences of C iv variability had corresponding changes in Si iv. We do not find any correlation between the absolute change in strength in C iv and in Si iv, but the fractional change in strength tends to be greater in Si iv than in C iv. When both C iv and Si iv varied, those changes always occurred in the same sense (either getting weaker or stronger). We also include our full data set so far in this paper, which includes up to 10 epochs of data per quasar. The multi-epoch data show that the BAL changes were not generally monotonic across the full ∼5–8 yr time span of our observations, suggesting that the characteristic time-scale for significant line variations, and (perhaps) for structural changes in the outflows, is less than a few years. Coordinated variabilities between absorption regions at different velocities in individual quasars seem to favour changing ionization of the outflowing gas as the cause of the observed BAL variability. However, variability in limited portions of broad troughs fits naturally in a scenario where movements of individual clouds, or substructures in the flow, across our lines of sight cause the absorption to vary. The actual situation may be a complex mixture of changing ionization and cloud movements. Further discussion of the implications of variability, e.g. in terms of the size and location of the outflowing gas, will be presented in a forthcoming paper.

Broad absorption lines (BALs) in quasar spectra identify high velocity outflows that likely exist in all quasars and could play a major role in feedback to galaxy evolution. The variability of BALs can help us understand the structure, evolution, and basic physical properties of the outflows. Here we report on our first results from an ongoing BAL monitoring campaign of a sample of 24 luminous quasars at redshifts 1.2

We present a study of outflow and feedback in the well-known Seyfert 2 galaxy Markarian 573 using high angular resolution long-slit spectrophotometry obtained with the Hubble Space Telescope Imaging Spectrograph (STIS). Through analysis of the kinematics and ionization state of a biconical outflow region emanating from the nucleus, we find that the outflow does not significantly accelerate the surrounding host-galaxy interstellar gas and is too weak to be a strong ionization mechanism in the extended emission regions. Instead, the excitation of the extended regions is consistent with photoionization by the active nucleus. From energetics arguments we show that the nuclear outflow is slow and heavy and has a mechanical luminosity that is only ~1% of the estimated bolometric luminosity of the system. The energy in the outflow is able to mildly shape the gas in the extended regions but appears to be insufficient to unbind it, or even to plausibly disrupt star formation. These results are at odds with the picture of strong AGN feedback that has been invoked to explain certain aspects of galaxy evolution., Comment: 31 pages, 7 figures, 4 tables

(Abridged) We present STIS observations of 14 nearby low-luminosity active galactic nuclei, including 13 LINERs and 1 Seyfert, taken at multiple parallel slit positions centered on the galaxy nuclei and covering the H-alpha spectral region. For each galaxy, we measure the emission-line velocities, line widths, and strengths, to map out the inner narrow-line region structure. There is a wide diversity among the velocity fields: in a few galaxies the gas is clearly in disk-like rotation, while in other galaxies the gas kinematics appear chaotic or are dominated by radial flows with multiple velocity components. The [S II] line ratio indicates a radial stratification in gas density, with a sharp increase within the inner 10-20 pc, in the majority of the Type 1 objects. We examine how the [N II] 6583 line width varies as a function of aperture size over a range of spatial scales, extending from scales comparable to the black hole's sphere of influence to scales dominated by the host galaxy's bulge. For most galaxies in the sample, we find that the emission-line velocity dispersion is largest within the black hole's gravitational sphere of influence, and decreases with increasing aperture size toward values similar to the bulge stellar velocity dispersion measured within ground-based apertures. Future dynamical modeling in order to determine black hole masses for a few objects in this sample may be worthwhile, although disorganized motion will limit the accuracy of the mass measurements., 35 pages, 10 figures. To appear in AJ

The Unification Model for active galactic nuclei posits that Seyfert 2s are intrinsically like Seyfert 1s, but that their broad-line regions (BLRs) are hidden from our view. A Seyfert 2 nucleus that truly lacked a BLR, instead of simply having it hidden, would be a so-called "true" Seyfert 2. No object has as yet been conclusively proven to be one. We present a detailed analysis of four of the best "true" Seyfert 2 candidates discovered to date: IC 3639, NGC 3982, NGC 5283, and NGC 5427. None of the four has a broad H-alpha emission line, either in direct or polarized light. All four have rich, high-excitation spectra, blue continua, and Hubble Space Telescope (HST) images showing them to be unresolved sources with no host-galaxy obscuration. To check for possible obscuration on scales smaller than that resolvable by HST, we obtained X-ray observations using the Chandra X-ray Observatory. All four objects show evidence of obscuration and therefore could have hidden BLRs. The picture that emerges is of moderate to high, but not necessarily Compton-thick, obscuration of the nucleus, with extra-nuclear soft emission extended on the hundreds-of-parsecs scale that may originate in the narrow-line region. Since the extended soft emission compensates, in part, for the nuclear soft emission lost to absorption, both absorption and luminosity are likely to be severely underestimated unless the X-ray spectrum is of sufficient quality to distinguish the two components. This is of special concern where the source is too faint to produce a large number of counts, or where the source is too far away to resolve the extended soft X-ray emitting region., Comment: 26 pages, 12 figures, submitted to ApJ

Using archival Chandra observations of 19 LINERs we explore the X-ray properties of their inner kiloparsec to determine the origin of their nuclear X-ray emission, to investigate the presence of an AGN, and to identify the power source of the optical emission lines. The relative numbers of LINER types in our sample are similar to those in optical spectroscopic surveys. We find that diffuse, thermal emission is very common and is concentrated within the central few hundred parsec. The average spectra of the hot gas in spirals and ellipticals are very similar to those of normal galaxies. They can be fitted with a thermal plasma (kT~0.5 keV) plus a power law (photon index of 1.3-1.5) model. There are on average 3 detected point sources in their inner kiloparsec with L(0.5-10 keV)~10^37-10^40 erg/s. The average cumulative luminosity functions for sources in spirals and ellipticals are identical to those of normal galaxies. In the innermost circle of 2.5" radius in each galaxy we find an AGN in 12 of the 19 galaxies. The AGNs contribute a median of 60% of the 0.5-10 keV luminosity of the central 2.5" region, they have luminosities of 10^37-10^39 erg/s (Eddington ratios 10^-8 to 10^-5). The ionizing luminosity of the AGNs is not enough to power the observed optical emission lines in this particular sample. Thus, we suggest that the lines are powered either by the mechanical interaction of an AGN jet (or wind) with the circumnuclear gas, or by stellar processes, e.g. photoionization by post-AGB stars or young stars., Accepted by Ap.J. 23 pages, 8 figures, emulatepj format, images of fig 1 not included, for complete PDF preprint see http://www.astro.psu.edu/users/mce/preprints/

(Abridged) We study the nuclear star clusters in spiral galaxies of various Hubble types using spectra obtained with STIS on-board HST. We observed the nuclear clusters in 40 galaxies, selected from two previous HST/WFPC2 imaging surveys. The spectra provide a better separation of cluster light from underlying galaxy light than is possible with ground-based spectra. To infer the star formation history, metallicity and dust extinction, we fit weighted superpositions of single-age stellar population templates to the spectra. The luminosity-weighted age ranges from 10 Myrs to 10 Gyrs. The stellar populations of NCs are generally best fit as a mixture of populations of different ages. This indicates that NCs did not form in a single event, but instead they had additional star formation long after the oldest stars formed. On average, the sample clusters in late-type spirals have a younger luminosity-weighted mean age than those in early-type spirals (log(age/yr) = 8.37+/-0.25 vs. 9.23+/-0.21). The average cluster masses are smaller in late-type spirals than in early-type spirals (log(M/Msun) = 6.25+/-0.21 vs. 7.63+/-0.24), and exceed the masses typical of globular clusters. The cluster mass correlates strongly with both the Hubble type of the host galaxy and the luminosity of its bulge. The latter correlation has the same slope as the well-known correlation between supermassive black hole mass and bulge luminosity. The properties of both nuclear clusters and black holes are therefore intimately connected to the properties of the host galaxy.

The XBootes Survey is a 5-ks Chandra survey of the Bootes Field of the NOAO Deep Wide-Field Survey (NDWFS). This survey is unique in that it is the largest (9.3 deg^2), contiguous region imaged in X-ray with complementary deep optical and near-IR observations. We present a catalog of the optical counterparts to the 3,213 X-ray point sources detected in the XBootes survey. Using a Bayesian identification scheme, we successfully identified optical counterparts for 98% of the X-ray point sources. The optical colors suggest that the optically detected galaxies are a combination of z 10). These objects are likely high redshift and/or dust obscured AGN. These sources have generally harder X-ray spectra than sources with 0.1

We present results from a Chandra survey of the nine square degree Bootes field of the NOAO Deep Wide-Field Survey (NDWFS). This XBootes survey consists of 126 separate contiguous ACIS-I observations each of approximately 5000 seconds in duration. These unique Chandra observations allow us to search for large scale structure and to calculate X-ray source statistics o ver a wide, contiguous field of view with arcsecond angular resolution and uniform coverage. Optical spectroscopic follow-up observations and the rich NDWFS data set will allow us to identify and classify these X-ray selected sources. Using wavelet decomposition, we detect 4642 point sources with n $\ge$ 2 counts. In order to keep our detections ~99% reliable, we limit our list to sources with n $\ge$ 4 counts. The full 0.5--7 keV band n $\ge$ 4 count list has 3293 point sources. In addition to the point sources, 43 extended sources have been detected consistent, with the depth of these observations and the number counts of clusters. We present here the X-ray catalog for the XBootes survey, including source positions, X-ray fluxes, hardness ratios and their uncertainties. We calculate and present the differential number of sources per flux densit y interval, $N(S)$, for the point sources.

We present Hubble Space Telescope blue spectra at intermediate spectral resolution for the nuclei of 23 nearby disk galaxies. These objects were selected to have nebular emission in their nuclei, and span a range of emission-line classifications as well as Hubble types. In this paper we focus on the stellar population as revealed by the continuum spectral energy distribution measured within the central 0."13 (~8pc) of these galaxies. The data were modeled with linear combinations of single-age stellar population synthesis models. The large majority (~80%) of the surveyed nuclei have spectra whose features are consistent with a predominantly old (>5x10^9 yr) stellar population. Approximately 25% of these nuclei show evidence of a component with age younger than 1 Gyr, with the incidence of these stars related to the nebular classification. Successful model fits imply an average reddening corresponding to A_V~0.4 mag and stellar metallicity of (1--2.5) Z_sun. We discuss the implications of these results for the understanding of star formation history in the environment of quiescent and active supermassive black holes. Our findings reinforce the picture wherein Seyfert nuclei and the majority of low-ionization nuclear emission-line regions (LINERs) are predominantly accretion-powered, and suggest that much of the central star formation in Hii nuclei is actually circumnuclear.

We present Chandra X-ray observations of the radio-quiet QSO PG 2302+029. This quasar has a rare system of ultra-high-velocity (-56,000 km s-1) UV absorption lines that form in an outflow from the active nucleus. The Chandra data indicate that soft X-ray absorption is also present. We perform a joint UV and X-ray analysis, using photoionization calculations, to determine the nature of the absorbing gas. The UV and X-ray data sets were not obtained simultaneously. Nonetheless, our analysis suggests that the X-ray absorption occurs at high velocities in the same general region as the UV absorber. There are not enough constraints to rule out multizone models. In fact, the distinct broad and narrow UV line profiles clearly indicate that multiple zones are present. Our preferred estimates of the ionization and total column density in the X-ray absorber (log U = 1.6, NH = 1022.4 cm-2) overpredict the O VI λλ1032, 1038 absorption unless the X-ray absorber is also outflowing at ~56,000 km s-1, but they overpredict the Ne VIII λλ770, 780 absorption at all velocities. If we assume that the X-ray-absorbing gas is outflowing at the same velocity as the UV-absorbing wind and that the wind is radiatively accelerated, then the outflow must be launched at a radius of ≤1015 cm from the central continuum source. The smallness of this radius casts doubts on the assumption of radiative acceleration.

The nucleus of M87 displays a LINER spectrum at optical wavelengths, with a nuclear disk of nebulosity that is resolved by the Hubble Space Telescope. We present new results from optical and ultraviolet spectra of the central ~40pc as measured by HST. In contrast with previous results for the extended disk, the emission-line spectrum of the central region is best reproduced by a multi-component photoionization scenario, rather than shock heating. The nebular properties as well as energetic considerations suggest a transition on scales of several tens of parsecs, from predominantly photoionization by a central accretion source, to shock ionization within the disk. If this source is at all representative, it suggests that many LINERs may be composite in terms of the energetic processes that give rise to the emission spectrum. We also report measurements of resonance-line absorption for the nucleus. The absorption spectrum, like the emission lines, is characterized by low ionization. The absorption line measurements coupled with independent constraints suggests a total hydrogen column density of 10^19 - 10^20 cm^-2, outflowing from the galaxy center with a velocity of ~126 km/s. The kinematic signature of an outflow, along with evidence that the absorber covers the power-law continuum source but not the emission-line clouds, suggests that the absorbing matter is related to accretion phenomena in the nucleus. The presence of such an outflow resembles similar behaviour in luminous AGN, although the low ionization that characterizes LINERs is probably indicative of a different mode of accretion in these sources., Accepted for publication in the Astrophysical Journal

We present observations of the intrinsic absorption in the Seyfert 1 galaxy NGC 3783 obtained with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer (FUSE). We have combined 18 STIS and five FUSE observations to obtain a high signal-to-noise ratio averaged spectrum spanning 905-1730 A. The averaged spectrum reveals absorption in O VI, N V, C IV, N III, C III, and the Lyman lines up to Ly in the three blueshifted kinematic components previously detected in the STIS spectrum (at radial velocities of -1320, -724, and -548 km s-1). The highest velocity component exhibits absorption in Si IV. We also detect metastable C III in this component, indicating a high density in this absorber. No lower ionization lines, i.e., C II and Si II, are detected. A weak, fourth absorption component is tentatively detected in the high-ionization lines and Lyα and Lyβ at a radial velocity of -1027 km s-1. The Lyman lines reveal a complex absorption geometry. The strength of the higher order lines indicates that Lyα and Lyβ are saturated over much of the resolved profiles in the three strongest absorption components and that, therefore, their observed profiles are determined by the covering factor. We separate the individual covering factors of the continuum and emission-line sources as a function of velocity in each kinematic component using the Lyα and Lyβ lines. The covering factor of the broad-line region is found to vary dramatically between the cores of the individual kinematic components, ranging from 0 to 0.84. In addition, we find that the continuum covering factor varies with velocity within the individual kinematic components, decreasing smoothly in the wings of the absorption by at least 60%. Comparison of the effective covering factors derived from the H I results with those determined directly from the doublets reveals that the covering factor of Si IV is less than half that of H I and N V in the high-velocity component. In addition, the FWHMs of N III and Si IV are narrower than those of the higher ionization lines in this component. These results indicate there is substructure within this absorber. We also find evidence for structure in the column density profiles of the high-ionization lines in this component. We derive a lower limit on the total column (NH ≥ 1019 cm-2) and ionization parameter (U ≥ 0.005) in the low-ionization subcomponent of this absorber. The metastable-to-total C III column density ratio implies ne ≈ 109 cm-3 and an upper limit on the distance of the absorber from the ionizing continuum of R ≤ 8 × 1017 cm. The decreasing covering factor found in the wings of the absorption and the extreme compactness of the C III* absorber are suggestive of a clumpy absorption gas with a low volume filling factor.

We estimate the metallicity in the broad emission-line region of the redshift z=4.16 quasar, BR2248-1242, by comparing line ratios involving nitrogen to theoretical predictions. BR2248-1242 has unusually narrow emission lines with large equivalent widths, thus providing a rare opportunity to measure several line-ratio abundance diagnostics. The combined diagnostics indicate a metallicity of ~2 times solar. This result suggests that an episode of vigorous star formation occurred near BR2248-1242 prior to the observed z=4.16 epoch. The time available for this enrichment episode is only ~1.5 Gyr at z=4.16 (for H_{0}=65 km s^-1 Mpc^-1, Omega_{m}=0.3 and Omega_Lambda ~< 1). This evidence for high metallicities and rapid star formation is consistent with the expected early-epoch evolution of dense galactic nuclei., 8 pages, 3 figures. Prepared in AAStex. Submitted to the Astrophysical Journal Revised version: added 1 reference

We present new HST I-band images of a sample of 77 nearby, late-type spiral galaxies with low inclination. The main purpose of this catalog is to study the frequency and properties of nuclear star clusters. In 59 galaxies of our sample, we have identified a distinct, compact (but resolved), and dominant source at or very close to their photocenter. In many cases, these clusters are the only prominent source within a few kpc from the galaxy nucleus. We present surface brightness profiles, derived from elliptical isophote fits, of all galaxies for which the fit was successful. We use the fitted isophotes at radii larger than 2" to check whether the location of the cluster coincides with the photocenter of the galaxy, and confirm that in nearly all cases, we are truly dealing with ``nuclear'' star clusters. From analytical fits to the surface brightness profiles, we derive the cluster luminosities after subtraction of the light contribution from the underlying galaxy disk and/or bulge.

Synthetic spectra generated with the parameterized supernova synthetic-spectrum code SYNOW are compared to photospheric-phase spectra of Type Ib supernovae (SNe Ib). Although the synthetic spectra are based on many simplifying approximations, including spherical symmetry, they account well for the observed spectra. Our sample of SNe Ib obeys a tight relation between the velocity at the photosphere, as determined from the Fe II features, and the time relative to that of maximum light. From this we infer that the masses and the kinetic energies of the events in this sample were similar. After maximum light the minimum velocity at which the He I features form usually is higher than the velocity at the photosphere, but the minimum velocity of the ejected helium is at least as low as 7000 kms. Previously unpublished spectra of SN 2000H reveal the presence of hydrogen absorption features, and we conclude that hydrogen lines also were present in SNe 1999di and 1954A. Hydrogen appears to be present in SNe Ib in general, although in most events it becomes too weak to identify soon after maximum light. The hydrogen-line optical depths that we use to fit the spectra of SNe 2000H, 1999di, and 1954A are not high, so only a mild reduction in the hydrogen optical depths would be required to make these events look like typical SNe Ib. Similarly, the He I line optical depths are not very high, so a moderate reduction would make SNe Ib look like SNe Ic., Comment: 21 pages and 24 figures, submitted to ApJ

We present results of a program of high signal-to-noise spectroscopy for 44 QSOs at redshifts > 4 using the MMT and Keck observatories. The quasar spectra cover 1100 -- 1700 A in the rest frame for sources spanning a luminosity range of approximately 2 orders of magnitude. Comparisons between these data and spectra of lower redshift quasars reveal a high degree of similarity, although differences are present in the profiles and the strengths of some emission features. An examination of the luminosity dependence of the emission lines reveals evidence for a weak or absent Baldwin effect among z > 4 QSOs. We compare measurements for objects in our sample with results from other high redshift surveys characterized by different selection techniques. Distributions of equivalent widths for these different ensembles are consistent with a common parent population, suggesting that our sample is not strongly biased, or in any case, subject to selection effects that are not significantly different from other surveys, including the Sloan Digital Sky Survey. Based on this comparison, we tentatively conclude that the trends identified here are representative of high z QSOs. In particular, the data bolster indications of supersolar metallicities in these luminous, high-z sources, which support scenarios that assume substantial star formation at epochs preceding or concurrent with the QSO phenomena., Comment: 26 pages (incl. 9 figures), AASTeX v5.0, to appear in The Astrophysical Journal

Herein we analyse late-time (post-plateau; 103 < t < 1229 d) optical spectra of low-redshift (z < 0.016), hydrogen-rich Type IIP supernovae (SNe IIP). Our newly constructed sample contains 91 nebular spectra of 38 SNe IIP, which is the largest dataset of its kind ever analysed in one study, and many of the objects have complementary photometric data. We determined the peak and total luminosity, velocity of the peak, HWHM intensity, and profile shape for many emission lines. Temporal evolution of these values and various flux ratios are studied. We also investigate the correlations between these measurements and photometric observables, such as the peak and plateau absolute magnitudes and the late-time light curve decline rates in various optical bands. The strongest and most robust result we find is that the luminosities of all spectral features (except those of helium) tend to be higher in objects with steeper late-time V-band decline rates. A steep late-time V-band slope likely arises from less efficient trapping of gamma-rays and positrons, which could be caused by multidimensional effects such as clumping of the ejecta or asphericity of the explosion itself. Furthermore, if gamma-rays and positrons can escape more easily, then so can photons via the observed emission lines, leading to more luminous spectral features. It is also shown that SNe IIP with larger progenitor stars have ejecta with a more physically extended oxygen layer that is well-mixed with the hydrogen layer. In addition, we find a subset of objects with evidence for asymmetric Ni-56 ejection, likely bipolar in shape. We also compare our observations to theoretical late-time spectral models of SNe IIP from two separate groups and find moderate-to-good agreement with both sets of models. Our SNe IIP spectra are consistent with models of 12-15 M_Sun progenitor stars having relatively low metallicity (Z $\le$ 0.01)., resubmitted to MNRAS, 50 pages (29 of which are tables), 15 figures, 10 tables

A large reverberation mapping study of the Seyfert 1 galaxy NGC 7469 has yielded emission-line lags for Hbeta 4861 and He II 4686 and a central black hole mass measurement of about 10 million solar masses, consistent with previous measurements. A very low level of variability during the monitoring campaign precluded meeting our original goal of recovering velocity-delay maps from the data, but with the new Hbeta measurement, NGC 7469 is no longer an outlier in the relationship between the size of the Hbeta-emitting broad-line region and the AGN luminosity. It was necessary to detrend the continuum and Hbeta and He II 4686 line light curves and those from archival UV data for different time-series analysis methods to yield consistent results., Comment: 9 Pages, 7 figures, 6 tables. Accepted for publication in The Astrophysical Journal

We present a study of the Type Ic supernova (SN) 1990B that includes most of the observations obtained from around the world. The combined data set comprises 84 BV(RI)c photometric points spanning approximately 360 days after maximum light and 14 spectra from 5 up to ~150 days after maximum light. In contrast to other Type Ic SNe, SN 1990B did not display a weak but distinct He I λ5876 line indicating that its He content was smaller or that the He layers were rather effectively shielded from the radioactive matter in the ejecta. The behavior of the Na I D line, however, suggests that He I λ5876 was blended with it. SN 1990B appeared on a sharply varying background that complicates the usual techniques of digital photometry. In order to do unbiased photometry, we modeled and subtracted the background of each image with the SN using images of NGC 4568 taken ~2500 days after the explosion, when SN 1990B had faded beyond detection. We compare the performance of standard point-spread function fitting photometry of the SN in the images with and without the background of the parent galaxy and find the results to differ systematically at late times. The photometry done on the images with the background light of NGC 4568 subtracted shows the light curves of SN 1990B to be of the slow Type Ic variety, with a slope steeper than that of the Type Ib SN 1983N or the Type II transition (Type IIb) SN 1993J but slower than that of the Type Ic SN 1994I. We estimate the reddening by foreground matter in the Galaxy and NGC 4568 and compute BV(RI)c light curves spanning ~110 days after maximum light.

Extended nebular filaments are seen at optical wavelengths in NGC 1275, the central galaxy in the Perseus cluster. The agents responsible for the excitation of these filaments remain poorly understood. In this paper we investigate possible mechanisms for powering the filaments, using measurements from an extensive spectroscopic data set acquired at the Lick Observatory 3-m Shane telescope. The results show that the filaments are in an extremely low ionization and excitation state. The high signal-to-noise ratio of the spectra allows us to measure or place sensitive upper limits on weak but important diagnostic lines. We compare the observed line intensity ratios to the predictions of various ionization models, including photoionization by an active galactic nucleus, shock heating, stellar photoionization, and photoionization by the intracluster medium. We also investigate possible roles for cluster extreme-ultraviolet emission, and filtering of cluster soft X-ray emission by an ionized screen, in the energetics of the filaments. None of these mechanisms provides an entirely satisfactory explanation for the physical state of the nebulae. Heating and ionization by reconnection of the intracluster magnetic field remains a potentially viable alternative, which merits further investigation through Faraday rotation studies., Accepted for publication in ApJ

Spectra taken with HST reveal that NGC 4450 emits Balmer emission lines with displaced double peaks and extremely high-velocity wings. This characteristic line profile, previously seen in a few nearby LINERs and in a small fraction of broad-line radio galaxies, can be interpreted as a kinematic signature of a relativistic accretion disk. We can reproduce the observed profile with a model for a disk with a radial range of 1000-2000 gravitational radii and inclined by 27 degrees along the line of sight. The small-aperture HST data also allow us to detect, for the first time, the featureless continuum at optical wavelengths in NGC 4450; the nonstellar nucleus is intrinsically very faint, with M_B = -11.2 mag for D = 16.8 Mpc. We have examined the multiwavelength properties of NGC 4450 collectively with those of other low-luminosity active nuclei which possess double-peaked broad lines and find a number of common features. These objects are all classified spectroscopically as "type 1" LINERs or closely related objects. The nuclear luminosities are low, both in absolute terms and relative to the Eddington rates. All of them have compact radio cores, whose strength relative to the optical nuclear emission places them in the league of radio-loud active nuclei. The broad-band spectral energy distributions of these sources are most notable for their deficit of ultraviolet emission compared to those observed in luminous Seyfert 1 nuclei and quasars. The double-peaked broad-line radio galaxies Arp 102B and Pictor A have very similar attributes. We discuss how these characteristics can be understood in the context of advection-dominated accretion onto massive black holes., Comment: To appear in The Astrophysical Journal. Latex, 15 pages, embedded figures and table

We discuss new Hubble Space Telescope spectroscopy of the radio-loud quasar, 3C 288.1. The data cover ~590 A to ~1610 A in the quasar rest frame. They reveal a wealth of associated absorption lines (AALs) with no accompanying Lyman-limit absorption. The metallic AALs range in ionization from C III and N III to Ne VIII and Mg X. We use these data and photoionization models to derive the following properties of the AAL gas: 1) There are multiple ionization zones within the AAL region, spanning a factor of at least ~50 in ionization parameter. 2) The overall ionization is consistent with the ``warm'' X-ray continuum absorbers measured in Seyfert 1 nuclei and other QSOs. However, 3) the column densities implied by the AALs in 3C 288.1 are too low to produce significant bound-free absorption at any UV-X-ray wavelengths. Substantial X-ray absorption would require yet another zone, having a much higher ionization or a much lower velocity dispersion than the main AAL region. 4) The total hydrogen column density in the AAL gas is log N_H (cm-2)= 20.2. 5) The metallicity is roughly half solar. 6) The AALs have deconvolved widths of ~900 km/s and their centroids are consistent with no shift from the quasar systemic velocity (conservatively within +/-1000 km/s). 7) There are no direct indicators of the absorber's location in our data, but the high ionization and high metallicity both suggest a close physical relationship to the quasar/host galaxy environment. Finally, the UV continuum shape gives no indication of a ``blue bump'' at higher energies. There is a distinct break of unknown origin at ~1030 A, and the decline toward higher energies (with spectral index alpha = -1.73, for f_nu ~ nu^alpha) is even steeper than a single power-law interpolation from 1030 A to soft X-rays.

We present a detailed comparison of optical H II region spectra to photoionization models based on modern stellar atmosphere models. We examine both spatially resolved and integrated emission-line spectra of the HII regions DEM L323, DEM L243, DEM L199, and DEM L301 in the Large Magellanic Cloud. The published spectral classifications of the dominant stars range from O7 to WN3, and morphologies range from Stromgren sphere to shell structure. Two of the objects include SNR contamination. The overall agreement with the predictions is generally within 0.2 dex for major diagnostic line ratios. An apparent pattern in the remaining discrepancies is that the predicted T_e is ~1000 K hotter than observed. (Abridged) Our analysis of the complex DEM L199 allows a nebular emission-line test of unprecedented detail for WR atmospheres. Surprisingly, we find no nebular He II 4686 emission, despite the fact that both of the dominant WN3 stars should be hot enough to fully ionize He I in their atmospheres. We confirm that the \eta-prime emission-line parameter is not as useful as hoped for determining the ionizing stellar effective temperature, T*. Both empirically and theoretically, we find that it is insensitive for T* >40 kK, and that it also varies spatially. The shock-contaminated objects show that \eta-prime will also yield a spuriously high T* in the presence of shocks. It is furthermore sensitive to shell morphology. We suggest [Ne III]/Hb as an additional probe of T*. Although it is abundance-dependent, [Ne III]/Hb has higher sensitivity to T*, is independent of morphology, and is insensitive to shocks in our objects. We attempt a first empirical calibration of these nebular diagnostics of T*., Comment: Accepted to ApJS. 37 pages, 14 figures, including 12 jpeg files. Uses emulateapj Latex style file. Single PS file preprint available at http://www.stsci.edu/~oey, along with unabridged abstract

We present spectroscopic observations from the Hubble Space Telescope that reveal for the first time the presence of a broad pedestal of Balmer-line emission in the LINER galaxy NGC 4203. The emission-line profile is suggestive of a relativistic accretion disk, and is reminiscent of double-peaked transient Balmer emission observed in a handful of other LINERs. The very broad line emission thus constitutes clear qualitative evidence for a black hole, and spatially resolved narrow-line emission in NGC 4203 can be used to constrain its mass, with M_BH less than 6 x 10^6 solar masses at 99.7% confidence. This value implies a ratio of black-hole mass to bulge mass of less than approximately 7 x 10^-4 in NGC 4203, which is less by a factor of ~3 - 9 than the mean ratio obtained for other galaxies. The availability of an independent constraint on central black-hole mass makes NGC4203 an important testbed for probing the physics of weak active galactic nuclei. Assuming M_BH near the detection limit, the ratio of observed luminosity to the Eddington luminosity is approximately 10^-4. This value is consistent with advection-dominated accretion, and hence with scenarios in which an ion torus irradiates an outer accretion disk that produces the observed double-peaked line emission. Follow-up observations will make it possible to improve the black-hole mass estimate and study variability in the nuclear emission., Comment: 10 pages (LaTeX, AASTeX v4.0), 2 postscript figures, accepted for publication in The Astrophysical Journal Letters

We present $J$-band ($1.15-1.35 \mu$m) spectroscopy of a sample of nine galaxies showing some degree of LINER activity (classical LINERs, weak-[O {\sc i}] LINERs and transition objects), together with $H$-band spectroscopy for some of them. A careful subtraction of the stellar continuum allows us to obtain reliable [Fe {\sc ii}]$1.2567 \mu$m/Pa$\beta$ line ratios. We conclude that different types of LINERs (i.e., photoionized by a stellar continuum or by an AGN) cannot be easily distinguished based solely on the [Fe {\sc ii}]$1.2567 \mu$m/Pa$\beta$ line ratio. The emission line properties of many LINERs can be explained in terms of an aging starburst. The optical line ratios of these LINERs are reproduced by a model with a metal-rich H {\sc ii} region component photoionized with a single stellar temperature $T_* = 38,000 $K, plus a supernova remnant (SNR) component. The [Fe {\sc ii}] line is predominantly excited by shocks produced by SNRs in starbursts and starburst-dominated LINERs, while Pa$\beta$ tracks H {\sc ii} regions ionized by massive young stars. The contribution from SNRs to the overall emission line spectrum is constrained by the [Fe {\sc ii}]$1.2567 \mu$m/Pa$\beta$ line ratio. Although our models for aging starbursts are constrained only by these infrared lines, they consistently explain the optical spectra of the galaxies also. The LINER-starburst connection is tested by predicting the time dependence of the ratio of the ionizing luminosity ($L_{\rm ion}$) to the supernova rate (SNr), $L_{\rm ion}$/(SNr). We predict the relative number of starbursts to starburst-dominated LINERs (aging starbursts) and show that it is in approximate agreement with survey findings for nearby galaxies., Comment: Accepted in ApJ (19 pages, 8 figures, uses emulateapj.sty)

We investigate the properties of the low-ionization nuclear emission region line (LINER) galaxy NGC4594 using data taken with the Hubble Space Telescope (HST) and the ASCA X-ray observatory.

NeVIII 774 is an important tracer of the high-ionization gas in QSOs. We examine the NeVIII emission-line properties using new HST-FOS spectra of four sources, mean spectra derived from two QSO samples in the HST archives, and new photoionization calculations. The results support our previous claim that broad NeVIIIlines are common in QSOs, with an average flux of ~42% of OVI 1034 and velocity widths that are ~2 to 5 times larger than OVI, CIV 1549 and other broad lines in the same spectra. The strongest and most reliably measured NeVIII 774 lines (in two sources) have FWHM ~ 14,500 km/s. Line profile fits in these cases show that the unusually large widths might be caused by blending with emission from NIV 765 and OIV~\lam 789. However, standard photoionization calculations indicate that NIV, OIV and all other lines near this wavelength should be too weak, leaving (very broad) NeVIII as the only viable identification for the ~774 A feature. (This conclusion might be avoided if there are large radial velocity dispersions [>~1000 km/s] in the emitting region and the resonant absorption of continuum photons enhances the flux in weaker lines.) The calculations also indicate that the NeVIII emitting regions have ionization parameters in the range 5 > U > 30, total hydrogen column densities of 10^22 < N_H < 3 x 10^23 cm-2, and an average covering factor of >30% (for solar abundances and a nominal QSO continuum shape). The NeVIII emitting region is therefore more extensive, more highly ionized, and has much higher velocities than the rest of the broad emission line region (BELR). This highly-ionized BELR component would be a strong X-ray ``warm'' absorber if it lies along our line-of-sight to the X-ray continuum source., 17 pages (LaTeX) plus 12 figures in one file (*.ps.gz), in press with ApJ

The Seyfert 1 nucleus of NGC 3783 shows intrinsic absorption in ultraviolet (UV) resonance lines as well as in soft X-rays. We review existing measurements of these features and use them to place constraints on the physical conditions in the absorbing media. We find that the observed column densities are consistent with a single-phase, photoionized plasma responsible for absorption in both bandpasses, although alternative scenarios in which the UV and X-ray continuum sources are covered by distinct clouds are not excluded. If the UV and X-ray absorbers constitute a single medium in at least approximate ionization equilibrium with the nuclear radiation field, observed variability in the strength of absorption can be used to derive a lower bound on the absorber's electron density of ne 50 cm-3. This result additionally implies an upper limit of about 30 pc for the separation between the nuclear continuum source and the absorbing plasma.

Quasar accretion disk winds observed via broad absorption lines (BALs) in the UV produce strong continuous absorption in X-rays. The X-ray absorber is believed to serve critically as a radiative shield to enable radiative driving. However, "mini-BAL" and narrow absorption line outflows have dramatically less X-ray absorption than BALs. Here we examine X-ray and rest-frame UV spectra of 8 mini-BAL quasars with outflow speeds in the range 0.1c to 0.2c to test whether extreme speeds require a strong shield. We find that the X-ray absorption is weak or moderate, with neutral-equivalent column densities N_H < few times 10^22 cm^-2, consistent with mini-BALs at lower speeds. We use photoionization models to show that this amount of shielding is too weak to control the outflow ionizations and, therefore, it is not important for the acceleration. Shielding in complex geometries also seems unlikely because the alleged shield would need to extinguish the ionizing far-UV flux while avoiding detection in X-rays and the near-UV. We argue that the outflow ionizations are kept moderate, instead, by high gas densities in small clouds. If the mini-BALs form at radial distances of order R ~ 2 pc from the central quasar (broadly consistent with theoretical models and with the mini-BAL variabilities observed here and in previous work), and the total column densities in the mini-BAL gas are N_H ~< 10^21 cm^-2, then the total radial extent of outflow clouds is only Delta-R_clouds ~< 3 x 10^13 cm and the radial filling factor is Delta-R_clouds/R ~< 5 x 10^-6 for weak/negligible shielding. Compared to the transverse sizes >~ 8 x 10^15 cm (based on measured line depths), the outflows have shapes like thin "pancakes" viewed face-on, or they occupy larger volumes like a spray of many dense clouds with a small volume filling factor. These results favor models with magnetic confinement in magnetic disk winds., 18 pages, 5 figures, accepted for publication in the MNRAS

The physical properties and dynamical behavior of Broad Absorption Line (BAL) outflows are crucial themes in understanding the connections between galactic centers and their hosts. FeLoBALs (identified with the presence of low-ionization Fe II BALs) are a peculiar class of quasar outflows that constitute approximately 1% of the BAL population. With their large column densities and apparent outflow kinetic luminosities, FeLoBALs appear to be exceptionally powerful and are strong candidates for feedback in galaxy evolution. We conducted variability studies of 12 FeLoBAL quasars with emission redshifts between 0.69 and 1.93, spanning both weekly and multi-year timescales in the quasar's rest frame. We detected absorption-line variability from low-ionization species (Fe II, Mg II) in four of our objects, with which we established a representative upper limit for the distance of the absorber from the supermassive black hole (SMBH) to be approximately 20 parsecs. Our goals are to understand the mechanisms producing the variability (e.g. ionization changes or gas traversing our line of sight) and place new constraints on the locations, structure, and kinetic energies of the outflows., Comment: 2 pages, no figures, to be published in conference proceedings for IAU Symposium No. 304: Multiwavelength AGN Surveys and Studies

We present the results from a detailed analysis of photometric and spectrophotometric data on five Seyfert 1 galaxies observed as a part of a recent reverberation mapping program. The data were collected at several observatories over a 140-day span beginning in 2010 August and ending in 2011 January. We obtained high sampling-rate light curves for Mrk 335, Mrk 1501, 3C120, Mrk 6, and PG2130+099, from which we have measured the time lag between variations in the 5100 Angstrom continuum and the H-beta broad emission line. We then used these measurements to calculate the mass of the supermassive black hole at the center of each of these galaxies. Our new measurements substantially improve previous measurements of MBH and the size of the broad line-emitting region for four sources and add a measurement for one new object. Our new measurements are consistent with photoionization physics regulating the location of the broad line region in active galactic nuclei., 45 pages, 5 figures. Accepted for publication in ApJ. For a brief video explaining the key results of this paper, see http://www.youtube.com/user/OSUAstronomy

Broad absorption lines (BALs) in quasar spectra are prominent signatures of high-velocity outflows, which might be present in all quasars and could be a major contributor to feedback to galaxy evolution. Studying the variability in these BALs allows us to further our understanding of the structure, evolution, and basic physical properties of the outflows. This is the third paper in a series on a monitoring programme of 24 luminous BAL quasars at redshifts 1.2 < z < 2.9. We focus here on the time-scales of variability in CIV 1549A BALs in our full multi-epoch sample, which covers time-scales from 0.02-8.7 yr in the quasar rest-frame. Our sample contains up to 13 epochs of data per quasar, with an average of 7 epochs per quasar. We find that both the incidence and the amplitude of variability are greater across longer time-scales. Part of our monitoring programme specifically targeted half of these BAL quasars at rest-frame time-scales, 16 pages, 15 figures, accepted for publication in MNRAS

We report Chandra observations of the Scd galaxy NGC 2139, which is known to host a recently formed (10^7.6 yrs) nuclear star cluster. The star cluster is undetected in X-rays, with an upper bound on 0.5-7 keV luminosity of L_X < 7.1 x 10^37 erg/s. This bound implies a bolometric accretion luminosity 10^39 erg/s. We use archival Hubble Space Telescope images to identify candidate optical counterparts for seven Chandra sources, which in most cases have optical luminosities and spatial profiles consistent with star clusters. Compared with other galaxies, the number of luminous X-ray sources in NGC 2139 is larger by a factor of 4 - 10 than expected based on its present star formation rate and stellar mass. This finding can be understood if NGC 2139 has concluded a burst of star formation in the recent past, and suggests that this galaxy could be important for testing the use of X-ray source populations as a chronometer of star formation history., 17 pages, 3 figures, accepted for publication in AJ

We quantify quasar color-variability using an unprecedented variability database - ugriz photometry of 9093 quasars from SDSS Stripe 82, observed over 8 years at ~60 epochs each. We confirm previous reports that quasars become bluer when brightening. We find a redshift dependence of this blueing in a given set of bands (e.g. g and r), but show that it is the result of the flux contribution from less-variable or delayed emission lines in the different SDSS bands at different redshifts. After correcting for this effect, quasar color-variability is remarkably uniform, and independent not only of redshift, but also of quasar luminosity and black hole mass. The color variations of individual quasars, as they vary in brightness on year timescales, are much more pronounced than the ranges in color seen in samples of quasars across many orders of magnitude in luminosity. This indicates distinct physical mechanisms behind quasar variability and the observed range of quasar luminosities at a given black hole mass - quasar variations cannot be explained by changes in the mean accretion rate. We do find some dependence of the color variability on the characteristics of the flux variations themselves, with fast, low-amplitude, brightness variations producing more color variability. The observed behavior could arise if quasar variability results from flares or ephemeral hot spots in an accretion disc., Comment: Accepted for publication in ApJ - in press, 17 pages, 14 figures - v2: abstract typo corrected & reference clean-up

We present results of five years of optical (UBVRI) observations of the very-high-energy gamma-ray blazar 1ES 1011+496 at the MDM Observatory. We calibrated UBVRI magnitudes of five comparison stars in the field of the object. Most of our observations were done during moderately faint states of 1ES 1011+496 with R > 15.0. The light curves exhibit moderate, closely correlated variability in all optical wavebands on time scales of a few days. A cross-correlation analysis between optical bands does not show significant evidence for time lags. We find a positive correlation (Pearson's r = 0.57; probability of non-correlation P(>r) ~ 4e-8) between the R-band magnitude and the B - R color index, indicating a bluer-when-brighter trend. Snap-shot optical spectral energy distributions (SEDs) exhibit a peak within the optical regime, typically between the V and B bands. We find a strong (r = 0.78; probability of non-correlation P (>r) ~ 1e-15) positive correlation between the peak flux and the peak frequency, best fit by a relation $��F_��^{\rm pk} \propto ��_{\rm pk}^k$ with k = 2.05 +/- 0.17. Such a correlation is consistent with the optical (synchrotron) variability of 1ES 1011+496 being primarily driven by changes in the magnetic field., Accepted for publication in ApJ. 16 pages, including 7 figures

Close to its center, the bulgeless galaxy NGC 2139 hosts a star cluster that is younger and less massive than any actual nuclear star cluster (NC) studied so far. We have measured the H-alpha velocity field around the photometric center of this galaxy using the VLT ARGUS integral field unit and GIRAFFE spectrograph in order to constrain different proposed theories of NC formation. We observe that the best-fit kinematic center and the candidate NC appear to be separated by 2.8 arcsec (320 pc). Indeed, the kinematic center also is offset from the galaxy's photometric center and a possible bar or extended region of star formation in which the young cluster resides, implying that this galaxy is not in dynamic equilibrium. The H-alpha flux map also reveals other regions of strong star formation in the possible bar. These observations suggest that a nascent NC is forming away from the kinematic center of NGC 2139 which may come to rest there on a time scale of a few 100 Myr., Accepted for publication in ApJ; 11 pages, 7 figures, Replaced figure 3 with correct version