Λ5007 Line Research Articles

A New Approach to the Internal Calibration of Reverberation-Mapping Spectra

We present a new procedure for the internal (night-to-night) calibration of timeseries spectra, with specific applications to optical AGN reverberation mapping data. The traditional calibration technique assumes that the narrow [O iii] λ5007 emission-line profile is constant in time; given a reference [O iii] λ5007 line profile, nightly spectra are aligned by fitting for a wavelength shift, a flux rescaling factor, and a change in the spectroscopic resolution. We propose the following modifications to this procedure: (1) we stipulate a constant spectral resolution for the final calibrated spectra, (2) we employ a more flexible model for changes in the spectral resolution, and (3) we use a Bayesian modeling framework to assess uncertainties in the calibration. In a test case using data for MCG+08-11-011, these modifications result in a calibration precision of ∼1 millimagnitude, which is approximately a factor of five improvement over the traditional technique. At this level, other systematic issues (e.g., the nightly sensitivity functions and Feii contamination) limit the final precision of the observed light curves. We implement this procedure as a python package (mapspec), which we make available to the community.

The wind-wind collision hole in eta Car

AbstractEta Carinae is one of the most massive observable binaries. Yet determination of its orbital and physical parameters is hampered by obscuring winds. However the effects of the strong, colliding winds changes with phase due to the high orbital eccentricity. We wanted to improve measures of the orbital parameters and to determine the mechanisms that produce the relatively brief, phase-locked minimum as detected throughout the electromagnetic spectrum. We conducted intense monitoring of the He ii λ4686 line in η Carinae for 10 months in the year 2014, gathering ~300 high S/N spectra with ground- and space-based telescopes. We also used published spectra at the FOS4 SE polar region of the Homunculus, which views the minimum from a different direction. We used a model in which the He ii λ4686 emission is produced by two mechanisms: a) one linked to the intensity of the wind-wind collision which occurs along the whole orbit and is proportional to the inverse square of the separation between the companion stars; and b) the other produced by the ‘bore hole’ effect which occurs at phases across the periastron passage. The opacity (computed from 3D SPH simulations) as convolved with the emission reproduces the behavior of equivalent widths both for direct and reflected light. Our main results are: a) a demonstration that the He ii λ4686 light curve is exquisitely repeatable from cycle to cycle, contrary to previous claims for large changes; b) an accurate determination of the longitude of periastron, indicating that the secondary star is ‘behind’ the primary at periastron, a dispute extended over the past decade; c) a determination of the time of periastron passage, at ~4 days after the onset of the deep light curve minimum; and d) show that the minimum is simultaneous for observers at different lines of sight, indicating that it is not caused by an eclipse of the secondary star, but rather by the immersion of the wind-wind collision interior to the inner wind of the primary.

THE METAL ABUNDANCES ACROSS COSMIC TIME (     ) SURVEY. I. OPTICAL SPECTROSCOPY IN THE SUBARU DEEP FIELD

ABSTRACT Deep rest-frame optical spectroscopy is critical for characterizing and understanding the physical conditions and properties of the ionized gas in galaxies. Here, we present a new spectroscopic survey called “Metal Abundances across Cosmic Time” or     , which will obtain rest-frame optical spectra for ∼3000 emission-line galaxies. This paper describes the optical spectroscopy that has been conducted with MMT/Hectospec and Keck/DEIMOS for ≈1900 z = 0.1–1 emission-line galaxies selected from our narrowband and intermediate-band imaging in the Subaru Deep Field. In addition, we present a sample of 164 galaxies for which we have measured the weak [O iii]λ4363 line (66 with at least 3σ detections and 98 with significant upper limits). This nebular emission line determines the gas-phase metallicity by measuring the electron temperature of the ionized gas. This paper presents the optical spectra, emission-line measurements, interstellar properties (e.g., metallicity, gas density), and stellar properties (e.g., star formation rates, stellar mass). Paper II of the     survey (Ly et al.) presents the first results on the stellar mass–gas metallicity relation at z ≲ 1 using the sample with [O iii]λ4363 measurements.

THE METAL ABUNDANCES ACROSS COSMIC TIME ( ) SURVEY. II. EVOLUTION OF THE MASS–METALLICITY RELATION OVER 8 BILLION YEARS, USING [O iii] λ4363 Å BASED METALLICITIES

ABSTRACT We present the first results from MMT and Keck spectroscopy for a large sample of emission-line galaxies selected from our narrowband imaging in the Subaru Deep Field. We measured the weak [O iii] λ4363 emission line for 164 galaxies (66 with at least 3σ detections, and 98 with significant upper limits). The strength of this line is set by the electron temperature for the ionized gas. Because the gas temperature is regulated by the metal content, the gas-phase oxygen abundance is inversely correlated with [O iii] λ4363 line strength. Our temperature-based metallicity study is the first to span Gyr of cosmic time and dex in stellar mass for low-mass galaxies, –9.0. Using extensive multi-wavelength photometry, we measure the evolution of the stellar mass–gas metallicity relation and its dependence on dust-corrected star formation rate (SFR). The latter is obtained from high signal-to-noise Balmer emission-line measurements. Our mass–metallicity relation is consistent with Andrews & Martini at , and evolves toward lower abundances at a given stellar mass, . We find that galaxies with lower metallicities have higher SFRs at a given stellar mass and redshift, although the scatter is large ( dex) and the trend is weaker than seen in local studies. We also compare our mass–metallicity relation against predictions from high-resolution galaxy formation simulations, and find good agreement with models that adopt energy- and momentum-driven stellar feedback. We identified 16 extremely metal-poor galaxies with abundances of less than a tenth of solar; our most metal-poor galaxy at is similar to I Zw 18.

Wolf-Rayet nebulae

Since the discovery of nebulae around Wolf-Rayet (WR) stars in the 1960s, it has been established that WR stars are massive stars at advanced evolutionary stages and that their surrounding nebulae result from the interactions between the stellar mass loss and the ambient interstellar medium. Surveys of WR nebulae have been made in the Galaxy, Magellanic Clouds, and other nearby galaxies in the Local Group. Some WR nebulae exhibit He II λ4686 line emission, indicating stellar effective temperatures of 90 — 100 x 103 K. The shocked fast stellar winds from WR nebulae have been detected in soft X-rays, but theoretical models have not been able to reproduce the observed X-ray spectral properties. Elemental abundances of WR nebulae consisting of synthesized stellar material can constrain stellar evolution models, but high-dispersion spectra are needed to kinematically separate the expanding shell of a WR nebula and the background interstellar medium for accurate abundance analyses.

IMAGING THE ELUSIVE H-POOR GAS IN THE HIGH adf PLANETARY NEBULA NGC 6778

ABSTRACT We present the first direct image of the high-metallicity gas component in a planetary nebula (NGC 6778), taken with the OSIRIS Blue Tunable Filter centered on the O ii λ4649+50 Å optical recombination lines (ORLs) at the 10.4 m Gran Telescopio Canarias. We show that the emission of these faint O ii ORLs is concentrated in the central parts of the planetary nebula and is not spatially coincident either with emission coming from the bright [O iii] λ5007 Å collisionally excited line (CEL) or the bright Hα recombination line. From monochromatic emission line maps taken with VIMOS at the 8.2 m Very Large Telescope, we find that the spatial distribution of the emission from the auroral [O iii] λ4363 line resembles that of the O ii ORLs but differs from nebular [O iii] λ5007 CEL distribution, implying a temperature gradient inside the planetary nebula. The centrally peaked distribution of the O ii emission and the differences with the [O iii] and H i emission profiles are consistent with the presence of an H-poor gas whose origin may be linked to the binarity of the central star. However, determination of the spatial distribution of the ORLs and CELs in other PNe and a comparison of their dynamics are needed to further constrain the geometry and ejection mechanism of the metal-rich (H-poor) component and hence, understand the origin of the abundance discrepancy problem in PNe.

ALFALFA DISCOVERY OF THE MOST METAL-POOR GAS-RICH GALAXY KNOWN: AGC 198691

ABSTRACT We present spectroscopic observations of the nearby dwarf galaxy AGC 198691. This object is part of the Survey of H i in Extremely Low-Mass Dwarfs project, which is a multi-wavelength study of galaxies with H i masses in the range of 106–107.2 M ⊙, discovered by the Arecibo Legacy Fast ALFA (ALFALFA) survey. We have obtained spectra of the lone H ii region in AGC 198691 with the new high-throughput KPNO Ohio State Multi-Object Spectrograph on the Mayall 4 m, as well as with the Blue Channel spectrograph on the MMT 6.5 m telescope. These observations enable the measurement of the temperature-sensitive [O iii]λ4363 line and hence the determination of a “direct” oxygen abundance for AGC 198691. We find this system to be an extremely metal-deficient (XMD) system with an oxygen abundance of 12+log(O/H) = 7.02 ± 0.03, making AGC 198691 the lowest-abundance star-forming galaxy known in the local universe. Two of the five lowest-abundance galaxies known have been discovered by the ALFALFA blind H i survey; this high yield of XMD galaxies represents a paradigm shift in the search for extremely metal-poor galaxies.

He II λ4686 EMISSION FROM THE MASSIVE BINARY SYSTEM IN η CAR: CONSTRAINTS TO THE ORBITAL ELEMENTS AND THE NATURE OF THE PERIODIC MINIMA* † ‡ §

ABSTRACT Eta Carinae (η Car) is an extremely massive binary system in which rapid spectrum variations occur near periastron. Most notably, near periastron the He ii λ4686 line increases rapidly in strength, drops to a minimum value, then increases briefly before fading away. To understand this behavior, we conducted an intense spectroscopic monitoring of the He ii λ4686 emission line across the 2014.6 periastron passage using ground- and space-based telescopes. Comparison with previous data confirmed the overall repeatability of the line equivalent width (EW), radial velocities, and the timing of the minimum, though the strongest peak was systematically larger in 2014 than in 2009 by 26%. The EW variations, combined with other measurements, yield an orbital period of 2022.7 ± 0.3 days. The observed variability of the EW was reproduced by a model in which the line flux primarily arises at the apex of the wind–wind collision and scales inversely with the square of the stellar separation, if we account for the excess emission as the companion star plunges into the hot inner layers of the primary’s atmosphere, and including absorption from the disturbed primary wind between the source and the observer. This model constrains the orbital inclination to 135°–153°, and the longitude of periastron to 234°–252°. It also suggests that periastron passage occurred on T 0 = 2456874.4 ( ± 1.3 ?> days). Our model also reproduced EW variations from a polar view of the primary star as determined from the observed He ii λ 4686 ?> emission scattered off the Homunculus nebula.

A DIRECT LINKAGE BETWEEN AGN OUTFLOWS IN THE NARROW-LINE REGIONS AND THE X-RAY EMISSION FROM THE ACCRETION DISKS

ABSTRACT The origin of outflow in the narrow-line region (NLR) of the active galactic nucleus (AGN) is studied in this paper by focusing on the relationship between the [O iii]λ5007 line profile and the hard-X-ray (in a bandpass of 2–10 keV) emission from the central super-massive black hole (SMBH) in type-I AGNs. A sample of 47 local X-ray selected type-I AGNs at z < 0.2 ?> is extracted from the 2XMMi/SDSS-DR7 catalog, which was originally cross-matched by Pineau et al. The X-ray luminosities in an energy band from 2 to 10 keV of these luminous AGNs range from 1042 to 10 44 erg s − 1 ?> . A joint spectral analysis is performed on their optical and X-ray spectra, in which the [O iii] line profile is modeled by a sum of several Gaussian functions to quantify its deviation from a pure Gaussian function. The statistics allow us to identify a moderate correlation with a significance level of 2.78σ: luminous AGNs with stronger [O iii] blue asymmetry tend to have steeper hard-X-ray spectra. By identifying the role of L / L Edd ?> on the correlation at a 2–3σ significance level in both direct and indirect ways, we argue that the photon index versus the asymmetry correlation provides evidence that the AGN’s outflow commonly observed in its NLR is related to the accretion process occurring around the central SMBH, which favors the wind/radiation model as the origin of the outflow in luminous AGNs.

REST-FRAME OPTICAL PROPERTIES OF LUMINOUS 1.5 < Z < 3.5 QUASARS: THE Hβ-[O iii] REGION

ABSTRACT We study the rest-frame optical properties of 74 luminous ( L bol = 10 46.2 − 48.2 erg s − 1 ?> ), 1.5 < z < 3.5 ?> broad-line quasars with near-IR (JHK) slit spectroscopy. Systemic redshifts based on the peak of the [O iii] λ5007 line reveal that redshift estimates from the rest-frame UV broad emission lines (mostly Mg ii) are intrinsically uncertain by ∼ 200 km s − 1 ?> (measurement errors accounted for). The overall full-width-at-half-maximum of the narrow [O iii] line is ∼ 1000 km s − 1 ?> on average. A significant fraction of the total [O iii] flux (∼40%) is in a blueshifted wing component with a median velocity offset of ∼ 700 km s - 1 ?> , indicative of ionized outflows within a few kpc from the nucleus; we do not find evidence of significant [O iii] flux beyond ∼ 10 kpc ?> in our slit spectroscopy. The [O iii] line is noticeably more asymmetric and weaker than that in typical less luminous low-z quasars. However, when matched in quasar continuum luminosity, low-z quasars have similar [O iii] profiles and strengths as these high-z systems. Therefore the exceptionally large width and blueshifted wing, and the relatively weak strength of [O iii] in high-z luminous quasars are mostly a luminosity effect rather than redshift evolution. The Hβ-[O iii] region of these high-z quasars displays a similar spectral diversity and Eigenvector 1 correlations with anti-correlated [O iii] and optical Fe ii strengths, as seen in low-z quasars; but the average broad Hβ width is larger by 25% than typical low-z quasars, indicating more massive black holes in these high-z systems. These results highlight the importance of understanding [O iii] in the general context of quasar parameter space in order to understand quasar feedback in the form of [O iii] outflows. The calibrated one-dimensional near-IR spectra are made publicly available, along with a composite spectrum.

NIR SPECTROSCOPIC OBSERVATION OF MASSIVE GALAXIES IN THE PROTOCLUSTER ATz= 3.09

We present the results of near-infrared spectroscopic observations of the K-band-selected candidate galaxies in the protocluster at z = 3.09 in the SSA22 field. We observed 67 candidates with KAB < 24 and confirmed redshifts of the 39 galaxies at 2.0 < zspec < 3.4. Of the 67 candidates, 24 are certainly protocluster members with 3.04 ⩽ zspec ⩽ 3.12, which are massive red galaxies that have been unidentified in previous optical observations of the SSA22 protocluster. Many distant red galaxies (J − KAB > 1.4), hyper extremely red objects (J − KAB > 2.1), Spitzer MIPS 24 μm sources, active galactic nuclei (AGNs) as well as the counterparts of Lyα blobs and the AzTEC/ASTE 1.1 mm sources in the SSA22 field are also found to be protocluster members. The mass of the SSA22 protocluster is estimated to be ∼2–5 × 1014 M☉, and this system is plausibly a progenitor of the most massive clusters of galaxies in the current universe. The reddest (J − KAB ⩾ 2.4) protocluster galaxies are massive galaxies with Mstar ∼ 1011 M☉ showing quiescent star formation activities and plausibly dominated by old stellar populations. Most of these massive quiescent galaxies host moderately luminous AGNs detected by X-ray. There are no significant differences in the [O iii] λ5007/Hβ emission line ratios and [O iii] λ5007 line widths and spatial extents of the protocluster galaxies from those of massive galaxies at z ∼ 2–3 in the general field.

Radiation fields of intermediate-age stellar populations with binaries as ionizing sources of H ii regions

Abstract Radiation fields emitted by O- and B-type stars or young stellar populations (SPs) are generally considered as significant central ionizing sources (CISs) of classic H ii regions. In our previous studies, we showed that the inclusion of binary interactions in stellar population synthesis models can significantly increase the ultraviolet spectrum hardness and the number of ionizing photons of intermediate-age (IA) SPs (7 ≲ log(t/yr) ≲ 8). In this work, we present photoionization models of H ii regions ionized by radiation fields emitted by IA SPs, including binary systems, and show that these fields are in theory possible candidates for significant CISs of classic H ii regions. When radiation fields of IA SPs comprising binary systems are used as the CISs of classic H ii regions, the theoretical strengths of a number of lines (such as [O iii] λ4959′, [S ii] λ6716′, etc.), which are weaker than observations, are increased; the border or selection-criterion lines between star-forming galaxies and active galactic nuclei (AGNs) in the diagnostic diagrams (for example, [N ii] λ6583/Hα versus [O iii] λ5007/Hβ), move into the region occupied originally by AGNs; and the He ii λ1640 line, observed in Lyman break and high-redshift gravitationally lensed galaxies, also can be produced.

Constraining the variation in the fine-structure constant using SDSS DR7 quasi-stellar object spectra

Abstract We report on a robust constraint on the possible variation of the fine-structure constant, α ≡ e2/ℏc, obtained using O iii λλ 4959,5007 nebular emission lines from quasi-stellar objects (QSOs). We find Δα/α = −(2.1 ± 1.6) × 10−5, based on a well-selected sample of 2347 QSOs from the Sloan Digital Sky Survey Data Release 7 with 0.02 &amp;lt;z &amp;lt; 0.74. Our result is consistent with a non-varying α at a level of 2 × 10−5 over approximately 7 Gyr. This is the largest sample of extragalactic objects yet used to constrain the variation of α. While this constraint is not as stringent as those determined using the many-multiplet method, it is free from various systematic effects. A factor of ∼4 improvement in Δα/α achieved here compared to a previous study is consistent with what is expected based on the sample used here, which is a factor of 14 times larger. This suggests that errors are mainly dominated by statistical uncertainty. We also find that the ratio of transition probabilities corresponding to the O iii λ5007 and λ4959 lines is 2.933 ± 0.002, in good agreement with the measurements of the National Institute of Standards and Technology.

Towards a dynamical mass of the ultraluminous X-ray source NGC 5408 X-1

We obtained multi-epoch Very Large Telescope optical spectroscopic data in 2011 and 2012 on the ultraluminous X-ray source NGC 5408 X-1. We confirm that the He ii λ4686 line has a broad component with an average full width at half-maximum of v = 780 ± 64 km s−1 with a variation of ∼13 per cent during observations spanning over four years, and is consistent with the origin in the accretion disc. The deepest optical spectrum does not reveal any absorption line from a donor star. Our aim was to measure the radial velocity curve and estimate the parameters of the binary system. We find an upper limit on the semi-amplitude of the radial velocity of K = 132 ± 42 km s−1. A search for a periodic signal in the data resulted in no statistically significant period. The mass function and constraints on the binary system imply a black hole mass of less than ∼510 M⊙. Whilst, a disc irradiation model may imply a black hole mass smaller than ∼431–1985 M⊙, depending on inclination. Our data can also be consistent with an unexplored orbital period range from a couple of hours to a few days, thus with a stellar-mass black hole and a subgiant companion.

Narrow-line region gas kinematics of 24 264 optically selected AGN: the radio connection

Using a sample of 24 264 optically selected active galactic nuclei (AGNs) from the SDSS DR7 data base, we characterize how the profile of the [O iii] λ5007 emission line relates to bolometric luminosity (LAGN), Eddington ratio, radio loudness, radio luminosity (L1.4 GHz) and optical class (i.e. broad/narrow-line Seyfert 1, type 2) to determine what drives the kinematics of this kpc-scale line emitting gas. First, we use spectral stacking to characterize how the average [O iii] λ5007 profile changes as a function of these five variables. After accounting for the known correlation between LAGN and L1.4 GHz, we report that L1.4 GHz has the strongest influence on the [O iii] λ5007 profile, with AGNs of moderate radio luminosity (L1.4 GHz = 1023–1025 W Hz−1) having the broadest [O iii] λ5007 profiles. Conversely, we find only a modest change in the [O iii] λ5007 profile with increasing radio loudness and find no significant difference between the [O iii] λ5007 profiles of broad- and narrow-line Seyfert 1s. When binned according to Eddington ratio, only the AGNs in our highest bin (i.e. >0.3) show any signs of having broadened [O iii] λ5007 profiles, although the small numbers of such extreme AGNs in our sample mean we cannot rule out that other processes (e.g. radio jets) are responsible for this broadening. The [O iii] λ5007 profiles of type 1 and type 2 AGNs show the same trends in terms of line width, but type 1 AGNs display a much stronger ‘blue wing’, which we interpret as evidence of outflowing ionized gas. We perform multicomponent fitting to the Hβ, [O iii] λλ4959, 5007, [N ii] λλ6548, 6584 and Hα lines for all the AGNs in our sample to calculate the proportions of AGNs with broad [O iii] λ5007 profiles. The individual fits confirm the results from our stacked spectra; AGNs with L1.4 GHz > 1023 W Hz−1 are roughly five times more likely to have extremely broad [O iii] λ5007 lines (full width at half-maximum, FWHMAvg > 1000 km s−1) compared to lower L1.4 GHz AGNs, and the width of the [O iii] λ5007 line peaks in moderate-radio-luminosity AGNs (L1.4 GHz ∼ 1024 W Hz−1). Our results are consistent with the most disturbed gas kinematics being induced by compact radio cores (rather than powerful radio jets), although broadened [O iii] λ5007 lines are also present, but much rarer, in low-L1.4 GHz systems. Our catalogue of multicomponent fits is freely available as an online resource for statistical studies of the kinematics and luminosities of the narrow- and broad-line AGN regions and the identification of potential targets for follow-up observations at http://sites.google.com/site/sdssalpaka.

IDENTIFICATION OF OUTFLOWS AND CANDIDATE DUAL ACTIVE GALACTIC NUCLEI IN SDSS QUASARS ATz= 0.8-1.6

We present a sample of 131 quasars from the Sloan Digital Sky Survey at redshifts 0.8 < z < 1.6 with double peaks in either of the high-ionization narrow emission lines [Ne v] λ3426 or [Ne iii] λ3869. These sources were selected with the intention of identifying high-redshift analogs of the z < 0.8 active galactic nuclei (AGNs) with double-peaked [O iii] λ5007 lines, which might represent AGN outflows or dual AGNs. Lines of high ionization potential are believed to originate in the inner, highly photoionized portion of the narrow line region, and we exploit this assumption to investigate the possible kinematic origins of the double-peaked lines. For comparison, we measure the [Ne v] λ3426 and [Ne iii] λ3869 double peaks in low-redshift (z < 0.8) [O iii]-selected sources. We find that [Ne v] λ3426 and [Ne iii] λ3869 show a correlation between line splitting and line width similar to that of [O iii] λ5007 in other studies, and the velocity splittings are correlated with the quasar Eddington ratio. These results suggest an outflow origin for at least a subset of the double peaks, allowing us to study the high-ionization gas kinematics around quasars. However, we find that a non-negligible fraction of our sample show no evidence for an ionization stratification. For these sources, the outflow scenario is less compelling, leaving the dual AGN scenario as a viable possibility. Finally, we find that our sample shows an anti-correlation between the velocity-offset ratio and luminosity ratio of the components, which is a potential dynamical argument for the presence of dual AGNs. Therefore, this study serves as a first attempt at extending the selection of candidate dual AGNs to higher redshifts.

The λ10830 He I Absorption Line Among Metal-Poor Subdwarfs

ABSTRACTSpectra of the He I λ10830 line have been obtained for 23 metal-poor stars, the majority of which are dwarfs ranging in metallicity from -2.1 ≤ [Fe/H] ≤ -0.8. The data were acquired with the NIRSPEC spectrograph on the Keck II telescope. Most of these subdwarfs and dwarfs are found to exhibit a He I absorption line indicative of the presence of chromospheres. The equivalent width of the λ10830 absorption profile is generally less than 70 mÅ, and covers a range similar to that found in solar metallicity stars of low activity. Among the subdwarfs the λ10830 equivalent width does not correlate with either [Fe/H] metallicity or (B - V) color. Some evidence for asymmetric profiles is found among metal-poor dwarfs, but not the high-speed blue-shifted absorption displayed by some metal-poor red giants.

Detecting Gas Outflows in Type-2 AGNs Selected from the Sloan Digital Sky Survey

AbstractEnergetic outflow from active galactic nuclei (AGNs) may play a critical role in galaxy evolution (e.g., Silk &amp; Rees 1998). We present a velocity diagnostic for detecting gas outflow in the narrow-line region of Type-2 AGNs using line-of-sight velocity offsets of the [O iii] λ5007 and Hα emission lines with respect to the systemic velocity of stars in host galaxies (See Figure 1). We apply the diagnostics to nearby galaxies at 0.02 &lt; z &lt; 0.05, 3775 AGN-host and 907 star-forming galaxies as a comparison sample, which are selected from the Sloan Digital Sky Survey DR7. After obtaining a best-fit stellar population model for the continuum and a systemic velocity based on stellar lines, we subtract the stellar component to measure velocity offsets of each emission line. We find a sample of 169 AGN-host galaxies with outflow signatures, displaying a larger velocity shift of [O iii] than that of Hα, as expected in a decelerating outflow model (Komossa et al. 2008). We find that the offset velocity of [O iii] increases with Eddington ratio, suggesting that gas outflow depends on the energetics of AGN.

Stellar population gradients in the cores of nearby field E+A galaxies

We have selected a sample of local E+A galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 7 for follow-up integral field spectroscopy with the Wide Field Spectrograph (WiFeS) on the Australian National University's (ANU) 2.3-m telescope. The sample was selected using the Hα line in place of the [O ii] λ3727 line as the indicator of ongoing star formation (or lack thereof). This allowed us to select a lower redshift sample of galaxies than available in the literature since the [O ii] λ3727 falls off the blue end of the wavelength coverage in the SDSS for the very lowest redshift objects. This low-redshift selection means that the galaxies have a large angular to physical scale which allows us to resolve the central ∼1 kpc region of the galaxies; the region where stellar population gradients are expected. Such observations have been difficult to make using other higher redshift samples because even at redshifts z∼ 0.1 the angular to physical scale is similar to the resolution provided by ground-based seeing. Our integral field spectroscopy has enabled us to make the first robust detections of Balmer line gradients in the centres of E+A galaxies. Six out of our sample of seven, and all the galaxies with regular morphologies, are observed to have compact and centrally concentrated Balmer line absorption. This is evidence for compact young cores and stellar population gradients which are predicted from models of mergers and tidal interactions which funnel gas into the galaxy core. Given the generally isolated nature of our sample, this argues for the galaxies being seen in the late stage of a merger where the progenitors have already coalesced.

HeII λ304 emission above sunspot umbrae

Observations of sunspot umbrae in the HeII λ304 A and HeI λ10830 A lines are analyzed and compared. Spectral observations in the HeI λ10830 line obtained on the Large Non-Eclipse Solar Coronograph of the Sayan Solar Observatory are used, together with HeII λ304 data obtained with the SOHO/EIT and CORONAS-f spacecraft. The contrast in the HeII λ304 line was chosen as an indicator of the UV flux. The dependences of the contrast in the HeII λ304 line and the parameters of the HeI λ10830 IR triplet on the sunspot area are obtained. The sunspot areas were determined using white-light images. A division of the dependences of the parameters of the HeI λ10830 and HeII λ304 lines on the sunspot area into two branches can be distinguished for leading and trailing sunspots. Possible origins of this behavior of the line parameters are discussed.