Extranuclear X-ray Emission in the Edge-on Seyfert Galaxy NGC 2992

We found several extranuclear (r >~ 3") X-ray nebulae within 40" (6.3 kpc at 32.5 Mpc) of the nucleus of the Seyfert galaxy NGC 2992. The net X-ray luminosity from the extranuclear sources is ~2-3 E39 erg/s (0.3-8.0 keV). The X-ray core itself (r <~ 1") is positioned at 9:45:41.95 -14:19:34.8 (J2000) and has a remarkably simple power-law spectrum with photon index Gamma=1.86 and Nh=7E21 /cm2. The near-nuclear (3" <~ r <~ 18") Chandra spectrum is best modelled by three components: (1) a direct AGN component with Gamma fixed at 1.86, (2) cold Compton reflection of the AGN component, and (3) a 0.5 keV low-abundance (Z < 0.03 Zsolar) "thermal plasma," with ~10% of the flux of either of the first two components. The X-ray luminosity of the 3rd component (the "soft excess") is ~1.4E40 erg/s, or ~5X that of all of the detected extranuclear X-ray sources. We suggest that most (~75-80%) of the soft excess emission originates from 1" < r < 3", which is not imaged in our observation due to severe CCD pile-up. We also require the cold reflector to be positioned at least 1" (158 pc) from the nucleus, since there is no reflection component in the X-ray core spectrum. Much of the extranuclear X-ray emission is coincident with radio structures (nuclear radio bubbles and large-scale radio features), and its soft X-ray luminosity is generally consistent with luminosities expected from a starburst-driven wind (with the starburst scaled from L_FIR). However, the AGN in NGC 2992 seems equally likely to power the galactic wind in that object. Furthermore, AGN photoionization and photoexcitation processes could dominate the soft excess, especially the \~75-80% which is not imaged by our observations.Comment: 34 pages AASTEX, 9 (low-res) PS figures, ApJ, in press. For full-resolution postscript file, visit http://www.pha.jhu.edu/~colbert/n2992_chandra.ps.g

Spitzer Observations of the z=2.73 Lensed Lyman Break Galaxy, MS1512-cB58

We present Spitzer infrared (IR) photometry and spectroscopy of the lensed Lyman break galaxy (LBG), MS1512-cB58 at z=2.73. The large (factor ~30) magnification allows for the most detailed infrared study of an L*_UV(z=3) LBG to date. Broadband photometry with IRAC (3-10 micron), IRS (16 micron), and MIPS (24, 70 & 160 micron) was obtained as well as IRS spectroscopy spanning 5.5-35 microns. A fit of stellar population models to the optical/near-IR/IRAC photometry gives a young age (~9 Myr), forming stars at ~98 M_sun/yr, with a total stellar mass of ~10^9 M_sun formed thus far. The existence of an old stellar population with twice the stellar mass can not be ruled out. IR spectral energy distribution fits to the 24 and 70 micron photometry, as well as previously obtained submm/mm, data give an intrinsic IR luminosity L_IR = 1-2 x10^11 L_sun and a star formation rate, SFR ~20-40 M_sun/yr. The UV derived star formation rate (SFR) is ~3-5 times higher than the SFR determined using L_IR or L_Halpha because the red UV spectral slope is significantly over predicting the level of dust extinction. This suggests that the assumed Calzetti starburst obscuration law may not be valid for young LBGs. We detect strong line emission from Polycyclic Aromatic Hydrocarbons (PAHs) at 6.2, 7.7, and 8.6 microns. The line ratios are consistent with ratios observed in both local and high redshift starbursts. Both the PAH and rest-frame 8 micron luminosities predict the total L_IR based on previously measured relations in starbursts. Finally, we do not detect the 3.3 micron PAH feature. This is marginally inconsistent with some PAH emission models, but still consistent with PAH ratios measured in many local star-forming galaxies.Comment: Accepted for publication in ApJ. aastex format, 18 pages, 7 figure

Application of Absorbing Boundary Condition to Nuclear Breakup Reactions

Absorbing boundary condition approach to nuclear breakup reactions is investigated. A key ingredient of the method is an absorbing potential outside the physical area, which simulates the outgoing boundary condition for scattered waves. After discretizing the radial variables, the problem results in a linear algebraic equation with a sparse coefficient matrix, to which efficient iterative methods can be applicable. No virtual state such as discretized continuum channel needs to be introduced in the method. Basic aspects of the method are discussed by considering a nuclear two-body scattering problem described with an optical potential. We then apply the method to the breakup reactions of deuterons described in a three-body direct reaction model. Results employing the absorbing boundary condition are found to accurately coincide with those of the existing method which utilizes discretized continuum channels.Comment: 21 pages, 5 figures, RevTeX

Far-ultraviolet imaging of the Hubble Deep Field-North: Star formation in normal galaxies at z < 1

We present far-ultraviolet (FUV) imaging of the Hubble Deep Field-North (HDF-N) taken with the Solar Blind Channel of the Advanced Camera for Surveys (ACS SBC) and the FUV MAMA detector of the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. The full WFPC2 deep field has been observed at 1600 Å. We detect 134 galaxies and one star down to a limit of FUV_(AB) ~ 29. All sources have counterparts in the WFPC2 image. Redshifts (spectroscopic or photometric) for the detected sources are in the range 0 < z < 1. We find that the FUV galaxy number counts are higher than those reported by GALEX, which we attribute at least in part to cosmic variance in the small HDF-N field of view. Six of the 13 Chandra sources at z < 0.85 in the HDF-N are detected in the FUV, and those are consistent with starbursts rather than active galactic nuclei. Cross-correlating with Spitzer sources in the field, we find that the FUV detections show general agreement with the expected L_(IR)/L_(UV) versus β relationship. We infer star formation rates (SFRs), corrected for extinction using the UV slope, and find a median value of 0.3 M_☉ yr^(-1) for FUV-detected galaxies, with 75% of detected sources having SFR < 1 M_☉ yr^(-1). Examining the morphological distribution of sources, we find that about half of all FUV-detected sources are identified as spiral galaxies. Half of morphologically selected spheroid galaxies at z < 0.85 are detected in the FUV, suggesting that such sources have had significant ongoing star formation in the epoch since z ~ 1

A First Estimate Of The X-Ray Binary Frequency As A Function Of Star Cluster Mass In A Single Galactic System

We use the previously-identified 15 infrared star-cluster counterparts to X-ray point sources in the interacting galaxies NGC 4038/4039 (the Antennae) to study the relationship between total cluster mass and X-ray binary number. This significant population of X-Ray/IR associations allows us to perform, for the first time, a statistical study of X-ray point sources and their environments. We define a quantity, \eta, relating the fraction of X-ray sources per unit mass as a function of cluster mass in the Antennae. We compute cluster mass by fitting spectral evolutionary models to K_s luminosity. Considering that this method depends on cluster age, we use four different age distributions to explore the effects of cluster age on the value of \eta and find it varies by less than a factor of four. We find a mean value of \eta for these different distributions of \eta = 1.7 x 10^-8 M_\sun^-1 with \sigma_\eta = 1.2 x 10^-8 M_\sun^-1. Performing a \chi^2 test, we demonstrate \eta could exhibit a positive slope, but that it depends on the assumed distribution in cluster ages. While the estimated uncertainties in \eta are factors of a few, we believe this is the first estimate made of this quantity to ``order of magnitude'' accuracy. We also compare our findings to theoretical models of open and globular cluster evolution, incorporating the X-ray binary fraction per cluster.Comment: 20 pages, 6 figures, accepted by Ap

Physical Properties of the X-ray Luminous SN 1978K in NGC 1313 from Multiwavelength Observations

We update the light curves from the X-ray, optical, and radio bandpasses which we have assembled over the past decade, and present two observations in the ultraviolet using the Hubble Space Telescope Faint Object Spectrograph. The HRI X-ray light curve is constant within the errors over the entire observation period. This behavior is confirmed in the ASCA GIS data obtained in 1993 and 1995. In the ultraviolet, we detected Ly-alpha, the [Ne IV] 2422/2424 A doublet, the Mg II doublet at 2800 A, and a line at ~3190 A we attribute to He I 3187. Only the Mg II and He I lines are detected at SN1978K's position. The optical light curve is formally constant within the errors, although a slight upward trend may be present. The radio light curve continues its steep decline. The longer time span of our radio observations compared to previous studies shows that SN1978K is in the same class of highly X-ray and radio-luminous supernovae as SN1986J and SN1988Z. The [Ne IV] emission is spatially distant from the location of SN1978K and originates in the pre-shocked matter. The Mg II doublet flux ratio implies the quantity of line optical depth times density of ~10^14 cm^-3 for its emission region. The emission site must lie in the shocked gas.Comment: 32 pages, 13 figs; LaTeX with AASTEXv5; paper accepted, scheduled for AJ, Dec 199

A Catalog of Candidate Intermediate-luminosity X-ray Objects

ROSAT, and now Chandra, X-ray images allow studies of extranuclear X-ray point sources in galaxies other than our own. X-ray observations of normal galaxies with ROSAT and Chandra have revealed that off-nuclear, compact, Intermediate-luminosity (Lx[2-10 keV] >= 1e39 erg/s) X-ray Objects (IXOs, a.k.a. ULXs [Ultraluminous X-ray sources]) are quite common. Here we present a catalog and finding charts for 87 IXOs in 54 galaxies, derived from all of the ROSAT HRI imaging data for galaxies with cz <= 5000 km/s from the Third Reference Catalog of Bright Galaxies (RC3). We have defined the cutoff Lx for IXOs so that it is well above the Eddington luminosity of a 1.4 Msun black hole (10^38.3 erg/s), so as not to confuse IXOs with ``normal'' black hole X-ray binaries. This catalog is intended to provide a baseline for follow-up work with Chandra and XMM, and with space- and ground-based survey work at wavelengths other than X-ray. We demonstrate that elliptical galaxies with IXOs have a larger number of IXOs per galaxy than non-elliptical galaxies with IXOs, and note that they are not likely to be merely high-mass X-ray binaries with beamed X-ray emission, as may be the case for IXOs in starburst galaxies. Approximately half of the IXOs with multiple observations show X-ray variability, and many (19) of the IXOs have faint optical counterparts in DSS optical B-band images. Follow-up observations of these objects should be helpful in identifying their nature.Comment: 29 pages, ApJS, accepted (catalog v2.0) (full resolution version of paper and future releases of catalog at http://www.xassist.org/ixocat_hri

The Spitzer Archival Far-InfraRed Extragalactic Survey

We present the Spitzer Archival Far-InfraRed Extragalactic Survey (SAFIRES). This program produces refined mosaics and source lists for all far-infrared extragalactic data taken during the more than six years of the cryogenic operation of the Spitzer Space Telescope. The SAFIRES products consist of far-infrared data in two wavelength bands (70 um and 160 um) across approximately 180 square degrees of sky, with source lists containing far-infrared fluxes for almost 40,000 extragalactic point sources. Thus, SAFIRES provides a large, robust archival far-infrared data set suitable for many scientific goals.Comment: 7 pages, 6 figures, published in ApJ

Detection of CO J=1-0 in the z=3.79 radio galaxy 4C60.07

We report on the detection of the lowest CO J = 1 - 0 transition in the powerful high-redshift radio galaxy 4C60.07 at z = 3.79. The CO emission is distributed in two spatially and kinematically distinct components as was previously known from the observations of the higher excitation CO J = 4 - 3 line. The total molecular gas mass in 4C60.07 inferred from the CO J = 1 - 0 emission is M(H_2) = 1.3 x 10^11 M_sun, sufficient to fuel the inferred star-formation rate of ~1600 M_sun yr^-1 for 10^8 yrs. From our high-resolution CO J = 1 - 0 VLA maps we find the dynamical mass of 4C60.07 to be comparable to that of a giant elliptical at the present time. A significant fraction of the mass is in the form of molecular gas suggesting that 4C60.07 is in an early state of its evolution. The merging nature of 4C60.07 along with its large dynamical mass imply that this system is a giant elliptical caught in its formative stages.Comment: 10 pages, 8 figures, Accepted for publication in Astronomy & Astrophysic

The X-ray Reflectors in the Nucleus of the Seyfert Galaxy NGC 1068

(abridged) Based on observations of the Seyfert nucleus in NGC1068 with ASCA, RXTE and BeppoSAX, we report the discovery of a flare (increase in flux by a factor of ~1.6) in the 6.7 keV Fe K line component between observations obtained 4 months apart, with no significant change in the other (6.21, 6.4, and 6.97 keV) Fe K_alpha line components. During this time, the continuum flux decreased by ~20%. The RXTE spectrum requires an Fe K absorption edge near 8.6 keV (Fe XXIII - XXV). The spectral data indicate that the 2-10 keV continuum emission is dominated (~2/3 of the luminosity) by reflection from a previously unidentified region of warm, ionized gas located <~ 0.2 pc from the AGN. The remaining ~1/3 of the observed X-ray emission is reflected from optically thick, neutral gas. The inferred properties of the warm reflector (WR) are: size (diameter) ~ 10^{5.5} /cm3, ionization parameter xi approx 10^{3.5} erg cm/s, and covering fraction 0.003 (L_0/10^{43.5} erg/s)^{-1} < (Omega/4 pi) < 0.024 (L_0/10^{43.5})^{-1}, where L_0 is the intrinsic 2-10 keV X-ray luminosity of the AGN. We suggest that the WR gas is the source of the (variable) 6.7 keV Fe line emission, and the 6.97 keV Fe line emission. The 6.7 keV line flare is assumed to be due to an increase in the emissivity of the WR gas from a decrease (by 20-30%) in L_0. The properties of the WR are most consistent with an intrinsically X-ray weak AGN with L_0 approx 10^{43.0} erg/s. The optical and UV emission that scatters from the WR into our line of sight is required to suffer strong extinction, which can be reconciled if the line-of-sight skims the outer surface of the torus. Thermal bremsstrahlung radio emission from the WR may be detectable in VLBA radio maps of the NGC 1068 nucleus.Comment: 39 pages (9 postscript figures) AASTEX, ApJ, accepte