Alpha Emission Line Research Articles

STAR FORMATION AND UV COLORS OF THE BRIGHTEST CLUSTER GALAXIES IN THE REPRESENTATIVEXMM-NEWTONCLUSTER STRUCTURE SURVEY

We present UV broadband photometry and optical emission-line measurements for a sample of 32 Brightest Cluster Galaxies (BCGs) in clusters of the Representative XMM-Newton Cluster Structure Survey (REXCESS) with z = 0.06-0.18. The REXCESS clusters, chosen to study scaling relations in clusters of galaxies, have X-ray measurements of high quality. The trends of star formation and BCG colors with BCG and host properties can be investigated with this sample. The UV photometry comes from the XMM Optical Monitor, supplemented by existing archival GALEX photometry. We detected H\alpha and forbidden line emission in 7 (22%) of these BCGs, in optical spectra. All of the emission-line BCGs occupy clusters classified as cool cores, for an emission-line incidence rate of 70% for BCGs in cool core clusters. Significant correlations between the H\alpha equivalent widths, excess UV production in the BCG, and the presence of dense, X-ray bright intracluster gas with a short cooling time are seen, including the fact that all of the H\alpha emitters inhabit systems with short central cooling times and high central ICM densities. Estimates of the star formation rates based on H\alpha and UV excesses are consistent with each other in these 7 systems, ranging from 0.1-8 solar masses per year. The incidence of emission-line BCGs in the REXCESS sample is intermediate, somewhat lower than in other X-ray selected samples (-35%), and somewhat higher than but statistically consistent with optically selected, slightly lower redshift BCG samples (-10-15%). The UV-optical colors (UVW1-R-4.7\pm0.3) of REXCESS BCGs without strong optical emission lines are consistent with those predicted from templates and observations of ellipticals dominated by old stellar populations. We see no trend in UV-optical colors with optical luminosity, R-K color, X-ray temperature, redshift, or offset between X-ray centroid and X-ray peak (<w>).

A long hard look at the minimum state of PG 2112+059 with XMM-Newton

XMM-Newton successfully detected the minimum state of PG 2112+059 during a short snapshot observation and performed a long follow-up observation. The high signal-to-noise spectra are modelled assuming different emission scenarios and compared with archival spectra taken by XMM-Newton and Chandra. The PG 2112+059 X-ray spectra acquired in May 2007 allowed the detection of a weak iron fluorescent line, which is interpreted as being caused by reflection from neutral material at some distance from the primary X-ray emitting source. The X-ray spectra of PG 2112+059 taken at five different epochs during different flux states can be interpreted within two different scenarios. The first consists of two layers of ionised material with column densities of N_H ~5 x 10^22 cm^-2 and N_H ~3.5 x 10^23 cm^-2, respectively. The first layer is moderately ionised and its ionisation levels follow the flux changes, while the other layer is highly ionised and does not show any correlation with the flux of the source. The spectra can also be interpreted assuming reflection by an ionised accretion disk seen behind a warm absorber. The warm absorber ionisation is consistent with being correlated with the flux of the source, which provides an additional degree of self-consistency with the overall reflection-based model. We explain the spectral variability with light bending according to the models of Miniutti and Fabian and constrain the black hole spin to be a/M > 0.86. Both scenarios also assume that a distant cold reflector is responsible for the Fe K \alpha emission line. Light bending provides an attractive explanation of the different states of PG 2112+059 and may also describe the physical cause of the observed properties of other X-ray weak quasars.

Helioseismic Network Provides Valuable Data

[1] I read with interest the editorial in Space Weather entitled “The need for long-term solar-terrestrial data series” (7, S05006, doi:10.1029/2009SW000496). As discussed in the editorial, it can be difficult to convince funding agencies of the value of long-term observational programs with consistent instrumentation over decades. I would like to point out that one such program, the Global Oscillation Network Group (GONG), which operates a set of six sites around the world to obtain helioseismic data of the Sun's interior, has been providing solar data since 1995. GONG has achieved an average 24-hour observing fraction of 85–90% since its beginning. Continual solar magnetic field measurements are also being provided by GONG, and data on the hydrogen alpha emission line will be provided to the U.S. Air Force starting in summer of 2010.

ASUZAKUOBSERVATION OF NGC 4593: ILLUMINATING THE TRUNCATED DISK

We report results from a 2007 Suzaku observation of the Seyfert 1 AGN NGC 4593. The narrow Fe K alpha emission line has a FWHM width ~4000 km/s, indicating emission from >~ 5000 Rg. There is no evidence for a relativistically broadened Fe K line, consistent with the presence of a radiatively efficient outer disk which is truncated or transitions to an interior radiatively inefficient flow. The Suzaku observation caught the source in a low-flux state; compared to a 2002 XMM observation, the hard X-ray flux decreased by 3.6, while the Fe K alpha line intensity and width each roughly halved. Two model-dependent explanations for the changes in Fe line profile are explored. In one, the Fe line width has decreased from ~10000 to ~4000 km/s from 2002 to 2007, suggesting that the thin disk truncation/transition radius has increased from 1000-2000 to >~5000 Rg. However, there are indications from other compact accreting systems that such truncation radii tend to be associated only with accretion rates relative to Eddington much lower than that of NGC 4593. In the second (preferred) model, the line profile in the XMM observation consists of a time-invariant narrow component plus a broad component originating from the inner part of the truncated disk (~300 Rg) which has responded to the drop in continuum flux. The Compton reflection component strength R is ~1.1, consistent with the measured Fe K alpha line total EQW with an Fe abundance 1.7 times solar. The modest soft excess has fallen by a factor of ~20 from 2002 to 2007, ruling out emission from a region 5 lt-yr in size.

Lyα RADIATIVE TRANSFER WITH DUST: ESCAPE FRACTIONS FROM SIMULATED HIGH-REDSHIFT GALAXIES

The Lyman alpha emission line is an essential diagnostic tool for probing galaxy formation and evolution. Not only is it commonly the strongest observable line from high-redshift galaxies but from its shape detailed information about its host galaxy can be revealed. However, due to the scattering nature of Lya photons increasing their path length in a non-trivial way, if dust is present in the galaxy the line may be severely suppressed and its shape altered. In order to interpret observations correctly, it is thus of crucial significance to know how much of the emitted light actually escapes the galaxy. In the present work, using a combination of high-resolution cosmological hydro-simulations and an adaptively refinable Monte Carlo Lya radiative transfer code including an advanced model of dust, the escape fractions f_esc of Lya radiation from high-redshift (z = 3.6) galaxies are calculated. In addition to the average escape fraction, the variation of f_esc in different directions and from different parts of the galaxies is investigated, as well as the effect on the emergent spectrum. Escape fractions from a sample of simulated galaxies of representative physical properties are found to decrease for increasing galaxy virial mass M_vir, from f_esc approaching unity for M_vir ~ 10^9 M_sun to f_esc less than 10% for M_vir ~ 10^12 M_sun. In spite of the dust being almost grey, it is found that the emergent spectrum is affected non-uniformly, with the escape fraction of photons close to the line center being much higher than of those in the wings, thus effectively narrowing the Lya line.

A large-scale survey of X-ray filaments in the Galactic Centre

We present a catalogue of 17 filamentary X-ray features located within a 68\times34 arcmin^2 view centred on the Galactic Centre region from images taken by Chandra. These features are described by their morphological and spectral properties. Many of the X-ray features have non-thermal spectra that are well fitted by an absorbed power law. Of the 17 features, we find six that have not been previously detected, four of which are outside the immediate 20\times20 arcmin^2 area centred on the Galactic Centre. Seven of the 17 identified filaments have morphological and spectral properties expected for pulsar wind nebulae (PWNe) with X-ray luminosities of 5\times10^32 to 10^34 erg s^-1 in the 2.0-10.0 keV band and photon indices in the range of \Gamma = 1.1 to 1.9. In one feature, we suggest the strong neutral Fe K\alpha emission line to be a possible indicator for past activity of Sgr A*. For G359.942-0.03, a particular filament of interest, we propose the model of a ram pressure confined stellar wind bubble from a massive star to account for the morphology, spectral shape and 6.7 keV He-like Fe emission detected. We also present a piecewise spectral analysis on two features of interest, G0.13-0.11 and G359.89-0.08, to further examine their physical interpretations. This analysis favours the PWN scenario for these features.

DETERMINING THE GALACTIC HALO'S EMISSION MEASURE FROM UV AND X-RAY OBSERVATIONS

We analyze a pair of Suzaku shadowing observations in order to determine the X-ray spectrum of the Galaxy's gaseous halo. We simultaneously fit the spectra with models having halo, local, and extragalactic components. The intrinsic intensities of the halo OVII triplet and OVIII Lyman alpha emission lines are 9.98^{+1.10}_{-1.99} LU (line unit; photons cm^-2 s^-1 Sr^-1) and 2.66^{+0.37}_{-0.30} LU, respectively. Meanwhile, FUSE OVI observations for the same directions and SPEAR CIV observations for a nearby direction indicate the existence of hot halo gas at temperatures of ~10^{5.0} K to ~10^{6.0} K. This collection of data implies that the hot gas in the Galactic halo is not isothermal, but its temperature spans a relatively wide range from ~10^{5.0} K to ~10^{7.0} K. We therefore construct a differential emission measure (DEM) model for the halo's hot gas, consisting of two components. In each, dEM/dlog T is assumed to follow a power-law function of the temperature and the gas is assumed to be in collisional ionizational equilibrium. The low-temperature component (LTC) of the broken power-law DEM model covers the temperature range of 10^{4.80}-10^{6.02} K with a slope of 0.30 and the high-temperature component (HTC) covers the temperature range of 10^{6.02}-10^{7.02} K with a slope of -2.21. We find that a simple model in which hot gas accretes onto the Galactic halo and cools radiatively cannot explain both the observed UV and X-ray portions of our broken power-law model. It can, however, explain the intensity in the Suzaku bandpass if the mass infall rate is 1.35*10^{-3} Msun yr^-1 kpc^-2. The UV and X-ray intensities and our broken power-law model can be well explained by hot gas produced by supernova explosions or by supernova remnants supplemented by a smooth source of X-rays.

On the peculiar properties of the narrow-line quasar PG 1543+489

We present the analysis of four XMM-Newton observations of the narrow-line quasar PG 1543+489 at z=0.400 carried out over a rest-frame time-scale of about three years. The X-ray spectrum is characterized by a broad, relativistic iron K_alpha emission line and a steep photon index, which can be both explained by a ionized reflection model, where the source of X-ray photons is presumably very close to the black hole. If this were the case, strong light-bending effects are expected, and actually they provide the most plausible explanation for the large equivalent width (EW=3.1+/-0.8 keV in the source rest frame) of the iron line. Although the light-bending model provides a good description of the X-ray data of PG 1543+489, it is not possible to rule out an absorption model, where obscuring matter partially covers the X-ray source. However, the apparent lack of variations in the properties of the absorber over the time-scale probed by our observations may indicate that this model is less likely.

Broadband X‐Ray Spectroscopy of A0535+262 withSuzaku

The transient X-ray binary pulsar A0535+262 was observed with Suzaku on 2005 September 14 when the source was in the declining phase of the August-September minor outburst. The ~103 s X-ray pulse profile was strongly energy dependent, a double peaked profile at soft X-ray energy band (<3 keV) and a single peaked smooth profile at hard X-rays. The width of the primary dip is found to be increasing with energy. The broad-band energy spectrum of the pulsar is well described with a Negative and Positive power-law with EXponential (NPEX) continuum model along with a blackbody component for soft excess. A weak iron K_alpha emission line with an equivalent width ~25 eV was detected in the source spectrum. The blackbody component is found to be pulsating over the pulse phase implying the accretion column and/or the inner edge of the accretion disk may be the possible emission site of the soft excess in A0535+262. The higher value of the column density is believed to be the cause of the secondary dip at the soft X-ray energy band. The iron line equivalent width is found to be constant (within errors) over the pulse phase. However, a sinusoidal type of flux variation of iron emission line, in phase with the hard X-ray flux suggests that the inner accretion disk is the possible emission region of the iron fluorescence line.

Gemini GMOS/IFU spectroscopy of NGC 1569 - I. Mapping the properties of a young star cluster and its environment

[Abridged] We present Gemini-North GMOS/IFU observations of a young star cluster (cluster 10) and its environment near the centre of the dwarf irregular starburst galaxy NGC 1569. This forms part of a larger and on-going study of the formation and collimation mechanisms of galactic winds, including three additional IFU pointings in NGC 1569 covering the base of the galactic wind which are analysed in a companion paper. The good spatial- and spectral-resolution of these GMOS/IFU observations, covering 4740-6860 A, allow us to probe the interactions between clusters and their environments on small scales. Combining our GMOS spectrum with HST imaging, we find that cluster 10 is composed of two very close components with ages of 5-7 Myr and <5 Myr, and a combined mass of 7 +/- 5 x 10^3 Msun. A detailed analysis of the H_alpha emission line profile shapes across the whole field-of-view shows them to be composed of a bright narrow feature (intrinsic FWHM ~ 50 km/s) superimposed on a fainter broad component (FWHM < 300 km/s). By mapping the properties of each individual component, we investigate the small-scale structure and properties of the ionized ISM, including reddening, excitation and electron densities, and for the first time find spatial correlations between the line component properties. We discuss in detail the possible mechanisms that could give rise to the two components and these correlations, and conclude that the most likely explanation for the broad emission is that it is produced in a turbulent mixing layer on the surface of the cool gas clumps embedded within the hot, fast-flowing cluster winds. We conclude we are sampling well within the outer bounding shocks of the expanding superbubbles and within the outflow 'energy injection zone'.

Efficient Kα x-ray source from submillijoule femtosecond laser pulses operated at kilohertz repetition rate

We report an efficient Cu K(alpha) x-ray source produced by focusing submillijoule, 120 fs Ti:sapphire laser pulses on a solid copper target to a spot diameter of few microns. The experimental results show strong emission of K(alpha) x-rays from solid targets from microplasmas created by p-polarized 0.2-0.3 mJ laser pulses at 1 kHz repetition rate. We have demonstrated K(alpha) x-ray point source emission rates of 6.7 x 10(9) photonss into 2 pi sr at 1 kHz repetition rate. The source has an x-ray conversion efficiency into Cu K(alpha) line emission of 3.2 x 10(-5). The source has a measured size of approximately 8 microm. Such a high repetition rate K(alpha) x-ray source can be very useful for time resolved x-ray diffraction and radiographic applications.

Observation of the Geocoronal Balmer Alpha with DEFPOS

Instrumental improvements in sensitivity of Fabry-Perot spectrometers with the development of Charged Coupled Device (CCD) cameras enable measurement of faint emission lines. A Dual Etalon Fabry-Perot Optical Spectrometer (DEFPOS) has recently been built to observe hydrogen Balmer alpha ( Hα : 6563 A) emission lines from the Earth’s upper atmosphere and the interstellar medium in our Galaxy. This spectrometer is now located at TUBITAK National Observatory (TUG), Antalya, Turkey, and has been observing in the zenith direction with a field-of-view of 4°.76 and with 1200 s exposure time. This paper briefly describes the DEFPOS spectrometer, data analysis, and results from data taken on 47 nights between 2002 and 2004. For the averaged geocoronal Balmer α intensities measured in nighttime, we found that the intensity was generally greater than 1 R and less than 12 R. These first results show that there is agreement with the theory and measurements made by other groups regarding the geocoronal Balmerα intensities. DEFPOS observations from Turkey offer potential to combine with geocoronal hydrogen observations at other locations such as Arecibo, Puerto Rico, Wisconsin Pine Bluff Observatory (PBO), and WHAM, Kitt Peak, Arizona, enhancing our global knowledge of the upper atmosphere. In the near future, DEFPOS will be used at coude exit of the 150 cm telescope. Then, it will be able to make more accurate observations at any direction in the sky.

Extended Lyman-α emission around bright quasars

Quasars trace the most massive structures at high redshifts and their presence may influence the evolution of the massive host galaxies. We study the extended Lyman alpha emission line regions (EELRs) around seven bright, mostly radio-quiet quasars (QSOs) at 2.7<z<4.5, and compare luminosities with EELRs around radio-loud QSOs reported in the literature. Using integral field spectroscopy, we analyse the morphology and kinematics of the quiescent Lya EELRs around the QSOs. We find evidence for the presence of EELRs around four radio-quiet and one radio-loud QSO. All EELRs appear asymmetric and the optically brightest QSOs also have the brightest Lya nebulae. For the two brightest nebulae we find velocities between ~600 km s^-1 at the QSO position to ~200 km s^-1 at a distance of 3-4 arcsec from the QSO and surface flux densities up to 2-3*10^{-16} erg cm^-2 s^-1 arcsec^-2. The five EELRs have total Lya luminosities which correspond to ~0.5% of the luminosities from the QSOs broad Lya emission lines. This fraction is an order of magnitude smaller than found for EELRs around radio-loud, steep spectrum QSOs reported in the literature. While the nebulae luminosities are correlated with the QSO Lya luminosities, we find that nebulae luminosities are not correlated with the central QSO ionising fluxes. The presence of gas in the EELRs can be interpreted based on two competing scenarios: either from quasar feedback mechanisms, or from infalling matter. Apart from these two effects, the Lya flux around radio-loud objects can be enhanced due to interactions with the radio jets. The relatively fainter nebulae around radio-quiet QSOs compared to lobe-dominated radio-loud QSOs can be ascribed to this effect, or to significant differences in the environments between the two classes.

A new detached K7 dwarf eclipsing binary system

We present an analysis of a new, detached, double-lined eclipsing binary system with K7 Ve components, discovered as part of the University of New South Wales Extrasolar Planet Search. The object is significant in that only 6 other binary systems are known with comparable or lower mass. Such systems offer important tests of mass-radius theoretical models. Follow-up photometry and spectroscopy were obtained with the 40-inch and 2.3m telescopes at SSO respectively. An estimate of the radial velocity amplitude from spectral absorption features, combined with the orbital inclination (83.5 deg) estimated from lightcurve fitting, yielded a total mass of M=(1.041 +/- 0.06)M_sun and component masses of M_A=(0.529 +/- 0.035)M_sun and M_B=(0.512 +/- 0.035)M_sun. The radial velocity amplitude estimated from absorption features (167 +/- 3)kmps was found to be less than the estimate from the H_alpha emission lines (175 +/- 1.5)kmps. The lightcurve fit produced radii of R_A=(0.641 +/- 0.05)R_sun and R_B=(0.608 +/- 0.06)R_sun, and a temperature ratio of T_B/T_A=0.980 +/- 0.015. The apparent magnitude of the binary was estimated to be V=13.9 +/- 0.2. Combined with the spectral type, this gave the distance to the binary as 169 +/- 14 pc. The timing of the secondary eclipse gave a lower limit on the eccentricity of the binary system of 0.0025 +/- 0.0005. This is the most statistically significant non-zero eccentricity found for such a system, possibly suggesting the presence of a third companion.

Tidally Triggered Star Formation in Close Pairs of Galaxies: Major and Minor Interactions

We study star formation in a sample of 345 galaxies in 167 pairs and compact groups drawn from the original CfA2 Redshift Survey and from a follow-up search for companions. We construct our sample with attention to including pairs with luminosity contrast |\Delta m_R| >= 2. These 57 galaxies with |\Delta m_R| >= 2 provide a set of nearby representative cases of minor interactions, a central feature of the hierarchical galaxy formation model. Here we report the redshifts and positions of the 345 galaxies in our sample, and of 136 galaxies in apparent pairs that are superpositions. In the pairs sample as a whole, there are strong correlations between the equivalent width of the H\alpha emission line and the projected spatial and the line-of-sight velocity separation of the pair. For pairs of small luminosity contrast, |\Delta m_R| = 2, we detect no correlation between the equivalent width of H\alpha and the projected spatial separation. The relative luminosity of the companion galaxy is more important in a gravitational tidal interaction than the intrinsic luminosity of the galaxy. Central star formation across the entire pairs sample depends strongly on the luminosity ratio, |\Delta m_R|, a reasonable proxy for the mass ratio of the pair; pairs composed of similarly luminous galaxies produce the strongest bursts of star formation. Pairs with |\Delta m_R| >= 2 rarely have EW(H\alpha) >~ 70 Ang.

Constraining Disk Parameters of Be Stars using Narrowband Hα Interferometry with the Navy Prototype Optical Interferometer

Abstract : Interferometric observations of two well-known Be stars, gamma Cas and phi Per, were collected and analyzed to determine the spatial characteristics of their circumstellar regions. The observations were obtained using the Navy Prototype Optical Interferometer equipped with custom-made narrowband filters. The filters isolate the H(alpha) emission line from the nearby continuum radiation, which results in an increased contrast between the interferometric signature due to the H(alpha)-emitting circumstellar region and the central star. Because the narrowband filters do not significantly attenuate the continuum radiation at wavelengths 50 nm or more away from the line, the interferometric signal in the H(alpha) channel is calibrated with respect to the continuum channels. The observations used in this study represent the highest spatial resolution measurements of the H -emitting regions of Be stars obtained to date. These observations allow us to demonstrate for the first time that the intensity distribution in the circumstellar region of a Be star cannot be represented by uniform disk or ringlike structures, whereas a Gaussian intensity distribution appears to be fully consistent with our observations.

Significant primordial star formation at redshifts z ≈ 3–4

Four recent observational results have challenged our understanding of high-redshift galaxies, as they require the presence of far more ultraviolet photons than should be emitted by normal stellar populations. First, there is significant ultraviolet emission from Lyman break galaxies (LBGs) at wavelengths shorter than 912 A. Second, there is strong Lyman alpha emission from extended 'blobs' with little or no associated apparent ionizing continuum. Third, there is a population of galaxies with unusually strong Lyman alpha emission lines. And fourth, there is a strong He II (1,640 A) emission line in a composite of LBGs. The proposed explanations for the first three observations are internally inconsistent, and the fourth puzzle has remained hitherto unexplained. Here we show that all four problems are resolved simultaneously if 10-30 per cent of the stars in many galaxies at z approximately 3-4 are mainly primordial--unenriched by elements heavier than helium ('metals'). Most models of hierarchical galaxy formation assume efficient intragalactic metal mixing, and therefore do not predict metal-free star formation at redshifts significantly below z approximately 5. Our results imply that micromixing of metals within galaxies is inefficient on an approximately gigayear timescale, a conclusion that can be verified with higher-resolution simulations, and future observations of the He ii emission line.

A complete view of the broad-line radio galaxy 4C +74.26 with XMM-Newton

This paper presents a timing study and broadband spectral analysis of the broad-line radio galaxy 4C+74.26 based on a 35 ks XMM-Newton observation. As found in previous datasets, the source exhibits no evidence for rapid variability, and its 0.2-10 keV lightcurve is well fit by a constant. An excellent fit to the pn 0.3-12 keV spectrum was found using a continuum that combines an ionized and a neutral reflector, augmented by both cold and warm absorption. There is no evidence for a soft excess. The column of cold absorption was greater than the Galactic value with an intrinsic column of \~1.9\times 10^{21} cm^{-2}. Evidence for the warm absorber was found from O VII and O VIII absorption edges with maximum optical depths of \tau_{O VII}=0.3 and \tau_{O VIII}=0.03, respectively. A joint pn-MOS fit increased the O VIII optical depth to \tau_{O VIII}=0.1. A simple, one-zone warm absorber model yielded a column of ~9\times 10^{20} cm^{-2} and an ionization parameter of \~60. Partial covering models provide significantly worse fits than ones including a relativistically broadened Fe K line, strengthening the case for the existence of such a line. On the whole, the X-ray spectrum of 4C+74.26 exhibits many features typical of both a radio-loud quasar (excess absorption) and radio-quiet Seyfert~1 galaxies (\fe emission and warm absorption). We also show that a spurious absorption line at ~8 keV can be created by the subtraction of an instrumental Cu K\alpha emission line.

High‐Resolution X‐Ray Spectrum of the Accreting Binary X‐Ray Pulsar GX 1+4

We present here high resolution X-ray spectrum of the accreting binary X-ray pulsar GX 1+4 obtained with the High Energy Transmission Grating (HETG) instrument of the Chandra X-ray Observatory. This was supplemented by a simultaneous observation with the Proportional Counter Array (PCA) of the Rossi X-ray Timing Explorer (RXTE). During this observation, the source was in a somewhat low intensity state and the pulse profile with both Chandra and RXTE shows a narrow dip, characteristic of GX 1+4 in medium and low intensity states. The continuum X-ray spectrum obtained with the HETG and PCA can be fitted well with a high energy cutoff power-law model with line of sight absorption. Interestingly, we find that this low state is accompanied by a relatively small absorption column density. A 6.4 keV narrow emission line with an equivalent width of 70 eV is clearly detected in the HETG spectrum. The fluorescence iron line, or at least part of it is produced in the neutral or lowly ionized iron in the circumstellar material that also causes most of the line of sight absorption. In the HETG spectrum, we have found evidence for a weak (equivalent width ~30 eV) emission line at 6.95 keV. This line is identified as Ly_alpha emission line from hydrogen-like iron and the spectrum does not show emission lines from helium-like iron. We discuss various emission regions for the hydrogen-like iron emission line, like gas diffused into the Alfven sphere or an accretion curtain flowing from the inner accretion disk to the magnetic poles.

Optical and near-infrared integral field spectroscopy of the SCUBA galaxy N2 850.4

We present optical and near-infrared integral field spectroscopy of the SCUBA galaxy SMMJ163650.43+ 405734.5 (ELAIS N2 850.4) at z = 2.385. We combine Ly alpha and H alpha emission line maps and velocity structure with high-resolution HST ACS and NICMOS imaging to probe the complex dynamics of this vigorous starburst galaxy. The imaging data show a complex morphology, consisting of at least three components separated by similar to 1 arcsec (8 kpc) in projection. When combined with the Ha velocity field from UKIRT UIST IFU observations we identify two components whose redshifts are coincident with the systemic redshift, measured from previous CO observations, one of which shows signs of AGN activity. A third component is offset by 220 +/- 50 km s(-1) from the systemic velocity. The total star-formation rate of the whole system ( estimated from the narrow-line H alpha and uncorrected for reddening) is 340 +/- 50 M-. yr(-1). The Ly alpha emission mapped by the GMOS IFU covers the complete galaxy and is offset by + 270 +/- 40 km s(-1) from the systemic velocity. This velocity offset is comparable to that seen in rest-frame UV-selected galaxies at similar redshifts and usually interpreted as a starburst-driven wind. The extended structure of the Ly alpha emission suggests that this wind is not a nuclear phenomenon, but is instead a galactic-scale outflow. Our observations suggest that the vigorous activity in N2 850.4 is arising as a result of an interaction between at least two dynamically-distinct components, resulting in a strong starburst, a starburst-driven wind and actively-fuelled AGN activity. Whilst these observations are based on a single object, our results clearly show the power of combining optical and near-infrared integral field spectroscopy to probe the power sources, masses and metallicities of far-infrared luminous galaxies, as well as understanding the role of AGN- and starburst-driven feedback processes in these high-redshift systems.