bluuebunny/crossref_metadata_2025 huggingface dataset:
The Optical Spectroscopic Properties of Seyfert 1 Galaxies Selected from Ultraluminous Infrared Galaxies
Authors: Xia X. Y. , Zheng X. Z. , Deng Z. G.
Published: July 2016

The ultraluminous infrared galaxies (ULIRGs) are strong interacting or merging galaxies. Statistical study shows that about ten percent of ULIRGs are QSOs or Seyfert 1 galaxies, and high–resolution HST images suggest that they are likely to be at the post merger stage. We investigate the optical spectroscopic properties for a complete sample of 28 QSOs/Seyfert 1s selected mainly from the IRAS galaxy redshift survey QDOT and 1.2 Jy catalogs. The optical spectra were obtained with the 2.16 m optical telescope of the Beijing Astronomical Observatory between October 1998 and the end of 1999. Statistical results for both continuum and emission lines show the following:

1. Most of our sample galaxies are strong or extremely strong FeII emitters with a ratio of FeII/Hβ larger than 2. There also exists an anti-correlation of the ratio of FeII/Hβ with EW(OIII) and FWHM(Hβ).

2. We fit the continuum for all sample galaxies. Aside from a few objects which could be fitted well by a power-law model, the continuum for most sample Seyfert 1 galaxies can be fitted well by a blackbody model or by composites of power–law and blackbody models. For Seyfert 1 galaxies which fit a power–law, E(B-V) is small and in the range of optically selected Seyfert 1 galaxies. However, for Seyfert 1 galaxies fitting a blackbody model, the temperature increases as E(B-V) increases. This is strong observational evidence to support the evolutionary scenario from starbursts to optical QSOs/Seyfert 1s.

3. We also discuss the possible mechanism for strong FeII emission from the point of view of evolution of mergers to AGNs.
Metallicity Evolution of Damped Lyman-α Systems
Authors: Savaglio Sandra
Published: July 2016

According to Pei, Fall, & Hauser (1999), the global metallicity evolution of the Universe can be represented by the ratio of the total metal content to the total gas content measured in damped Lyman–α (DLA) systems (the “column density weighted metallicity” à la Pettini). To minimize dust obscuration effects, a DLA sample with negligible dust content is considered, namely, 50 DLAs with log NHI < 20.8. The global metallicity found shows clear evidence of redshift evolution that goes from ~ 1/30 solar at z ~ 4.1 to solar at z ~ 0.4. More generally, DLAs with measured heavy elements probe the ISM of high redshift galaxies. The whole sample collected from the literature contains 75 DLAs. The metallicity is calculated adopting for the dust correction the most general method used so far, based on models of the ISM dust depletions in the Galaxy. The intrinsic metallicity evolution of DLA galaxies is d log ZDLA/dz = −0.33 ± 0.06.
The Oldest Stars as Tracers of Heavy Element Formation at Early Epochs
Authors: Truran James W.
Published: July 2016

Elemental abundance patterns in very metal-poor halo field stars and globular cluster stars play a crucial role both in guiding theoretical models of nucleosynthesis and in providing constraints upon the early star formation and concomitant nucleosynthesis history of our Galaxy. The abundance patterns characterizing the oldest and most metal deficient stars ([Fe/H] ≤ −3) are entirely consistent with their being products of metal-poor massive stars of lifetimes τ ≤ 108years. This includes both the elevated abundances of thealpha-elements (O, Mg, Si, S, Ca, and Ti) relative to iron-peak elements and the dominance of r-process elements over s-process elements. The nucleosynthetic contributions of lower mass AGB stars of longer lifetimes (τ ≈ 109years) begin to appear at metallicities [Fe/H] ≈ −2.5, while clear evidence for iron-peak nuclei produced in supernovae Ia (τ ≥ 1-2x109years?) does not appear until metallicities approaching [Fe/H] ~ −1. Similar trends are also suggested by abundances determined for gas clouds at high redshifts. We review the manner in which a knowledge of the abundances of the stellar and gas components of early populations, as a function of [Fe/H], time, and/or redshift, can be used to set constraints on their star formation and nucleosynthesis histories.
Searching for the Reionization Epoch
Authors: Shaver P. A.
Published: July 2016

Recent advances have led to the discoveries of both galaxies and quasars out to z ~ 6. The reionization epoch itself, thought to lie somewhere in the range 6 < zi < 15, may be within reach over the next decade. Prospects for the detection of the first luminous objects in the Universe are reviewed - the objects that reionized the Universe and brought an end to the “Dark Ages”. Alternative possibilities for detecting the reionization epoch are also discussed, including direct detection of the intergalactic medium itself at that epoch.
Cosmic Star Formation Rate at z ~ 3 — Metallicity Effect
Authors: Hirashita H. , Inoue A. K. , Kamaya H.
Published: July 2016

Infrared (IR) emission from Galactic dust is frequently used as an indicator of the star formation rate (SFR). Recently, A. K. Inoue, H. Hirashita, & H. Kamaya derived a formula for conversion from the IR luminosity to the SFR based on a physical model of H II regions (PASJ, 52, 539, 2000). They expressed this as SFR/(M⊙ yr−1) = {1.1 x 10-10(1-η)/(0.4–0.22f+0.6∊)}(LIR/L⊙), where f is the fraction of ionizing photons absorbed by hydrogen, ∊ is the efficiency of dust absorption for non-ionizing photons, η is the cirrus fraction of the observed dust luminosity, and LIR is the observed luminosity of dust emission. Since f depends on the dust-to-gas ratio and the dust-to-gas ratio is related to metallicity, we present the dependence of the formula on metallicity.

Our metallicity-dependent conversion formula is applied to the cosmic star formation history. Based on a recent model of the cosmic star formation history and metal enrichment history, we find that the photons from OB stars are not efficiently reprocessed in the IR before z ~ 3 because of a low dust-to-gas ratio. This indicates that the star formation rate estimated from the submillimeter luminosity using an empirical formula is significantly underestimated (by at least a factor of 3).
The ASTRO-F (IRIS) Mission
Authors: Shibai Hiroshi
Published: July 2016

ASTRO-F (IRIS) is the first Japanese satellite dedicated to infrared astronomy. The primary purpose of this project is to investigate the birth and evolution of galaxies in the early universe through deep, wide-field surveys at wavelengths ranging from 2 to 200 microns. The spatial resolution and the point source sensitivity are nearly the same as those of the aperture diffraction limit and the natural background and/or confusion limit, respectively. In the far-infrared wavelength band, ASTRO-F will conduct an all-sky survey like the IRAS survey with several tens of times higher sensitivity and several times better spatial resolution. In the near- and mid-infrared, wide area sky-surveys will be conducted over pre-selected portions of the sky. In addition to these photometric surveys, low-resolution spectroscopic capabilities are available for all wavelength bands. The ASTRO-F mission will produce a fundamental database for the next generation of advanced observatories, for example FIRST, and NGST, and will complement the SIRTF mission by virtue of its wide sky coverage. The launch by an M-V rocket is scheduled for February or March of 2004.
The FIRST ESA Cornerstone Mission
Authors: Pilbratt Göran L.
Published: July 2016

The ‘Far InfraRed and Submillimetre Telescope’ (FIRST) is the fourth cornerstone mission in the European Space Agency (ESA) science programme. It will perform imaging photometry and spectroscopy in the far infrared and submillimetre part of the spectrum, covering approximately the 60–670 μm range.

The key science objectives emphasize current questions connected to the formation of galaxies and stars, however, having unique capabilities in several ways.

FIRST, a facility available to the entire astronomical community, will carry a 3.5 metre diameter passively cooled telescope. The science pay-load complement – two cameras/medium resolution spectrometers (PACS and SPIRE), and a very high resolution heterodyne spectrometer (HIFI) – will be housed in a superfluid helium cryostat.

In early 2007, FIRST will be placed in a transfer trajectory towards its operational orbit around the Earth-Sun L2 point by an Ariane 5 (shared with the ESA cosmic background mapping mission, Planck). Once operational, FIRST will offer a minimum of 3 years of routine observations; roughly 2/3 of the available observing time is open to the general astronomical community through a standard competitive proposal procedure.
Spectroscopy and Geography of Magnetic Ap Stars: Implications for Structure
Authors: Landstreet J. D.
Published: July 2016

Some main sequence A and B stars have strong, ordered magnetic fields. These Ap and Bp stars usually have anomalous chemical abundances, and often rather non-uniform distributions of at least some elements (e.g. He, Ca, Ti, Cr) over their surfaces. Maps of magnetic field structure may provide a means of testing theories of how large coherent fields form, and of probing large-scale hydrodynamic flows (meridional circulation) inside stars. Maps of distributions of various elements can help to elucidate the mechanisms, such as diffusion under competing influences of gravity and radiation, turbulence, meridional circulation, mass loss, and perhaps accretion from the interstellar medium, that lead to the distinctive abundances and surface abundance distributions. This kind of mapping is important as an aid to understanding how the Ap and Bp stars develop. It is even more important because the processes involved in producing Ap and Bp stars probably have significant effects on surface chemical abundances of “normal” upper main sequence stars, and so understanding the relevant physics is essential to correctly relating observed surface chemistry to stellar and galactic evolution. In this paper, efforts to map field and abundance structures in Ap stars are reviewed, and some of the principal results obtained thus far are discussed.
The Chemical Composition of Asymptotic Giant Branch Stars-the s-process
Authors: Lambert David L.
Published: July 2016

This review discusses the chemical composition of AGB stars in the light of predictions for intermediate-mass (3-8 M⊙, 22Ne(α,n) = the neutron source) and low-mass (< 3 M⊙, 13C(α,n) = the neutron source) stars. LM-AGB models can be constructed with envelopes having a composition quite similar to that of solar system material, the SiC grains recently discovered in meteorites, and real AGB stars in the sequence of spectral types M → S → C. Stellar counterparts of the IM-AGB models have yet to be discovered.
Turbulence and the Lithium Abundance in Giants and Main-Sequence Disk and Halo Stars
Authors: Vauclair S.
Published: July 2016

The present situation concerning the observations of lithium in subgiant and giant stars is reviewed. These observations, compared to the determinations of lithium in main-sequence stars, can be used to obtain more stringents constraints on the dynamics of the stellar gas in the main-sequence as well as in the subgiant and giant stages. The macroscopic motions expected in stars are discussed from a theoretical point of view and compared to the observations, with special focusing on the theories of rotation-induced turbulence.
Chemical Compositions of Post-AGB Stars
Authors: Bond Howard E.
Published: July 2016

Objects that may be in a post-AGB evolutionary stage include high-latitude supergiants, UU Her and RV Tau variables, and IRAS sources identified with A- to G-type supergiants. Photospheric abundance analyses of such objects typically reveal moderate to extreme iron-group deficiencies, consistent with membership in the thick-disk or halo populations, and with having arisen from low-mass progenitors. The photospheric CNO abundance patterns in such stars are distinctly atypical of normal Population I supergiants, and appear to indicate the presence of helium-burning products at the stellar surface. However, enhancements of s-process elements are typically not seen, suggesting that most of the stars have avoided the AGB dredge-up. A subset of the stars, typified by HR 4049, show ultra-low iron-group abundances and extreme enhancements of C, N, O, and S. They appear to constitute a new class of chemically peculiar stars, with severely depleted photospheric metals. Grain formation is proposed as the depletion mechanism.
Binarity and Abundance Anomalies in Stars
Authors: Tutukov A. V.
Published: July 2016

About one half of all stars are close binaries whose components can efficiently interact during their evolution. The interaction of the components significantly influences the evolution and changes the chemical composition of their atmospheres. This review is devoted to the discussion of the binarity role in the creation of stars with an anomalous chemical composition of their envelopes: WR, OBN, OBC, RCrB, Ba, sdBO, Am, Fm, Ap, Bp, helium stars, CO stars, Na giants.
Atmospheres and Abundances of Blue Horizontal Branch Stars and Related Objects
Authors: Heber U.
Published: July 2016

Spectroscopic analyses of blue horizontal branch stars, subluminous B- and O-stars and PG 1159 stars are reviewed. These classes of stars trace stellar evolution from the horizontal branch towards the white dwarf cooling sequence. The impact of Non-LTE model atmospheres for the analyses of sdO and PG 1159 stars is outlined. The resulting atmospheric parameters and abundances are used to obtain constraints on the evolutionary status of the different classes of stars. The sdB stars form a homogeneous group and can be identified with models of the extended horizontal branch. Abundance anomalies (deficiency of helium and some metals, enrichment of 3He) observed in Horizontal Branch stars and sdB stars do not give hints to the stars' evolutionary history but are caused by atmospheric diffusion. The class of subluminous O stars is much less homogenous and two subclasses can be defined: the “compact” sdO stars probably evolved from the extended horizontal branch and are hence successors of the sdBs, whereas some sdOs of relatively low gravity are in a post-AGB stage of evolution. The third class, the PG 1159 stars, are amongst the hottest stars known with effective temperatures exceeding 100,000 K and are immediate progenitors of the white dwarfs. The abundance pattern is dominated by carbon and helium with a significant admixture of oxygen, whereas hydrogen and nitrogen are trace elements only. As in the case of the (helium rich) sdO stars these abundances indicate that nuclear processed material is exposed at the stellar surface. The origin of the PG 1159 stars as well as of the “low gravity” sdO stars can be explained by the born-again post-AGB star scenario of Iben et al. (1983).
Radio Measurement of the Time Delay in 0218+357
Authors: Corbett E.A. , Browne I.W.A. , Wilkinson P.N. , Patnaik A.R.
Published: July 2016

A time delay of 12±3 days has been measured for the lens system 0218+357 using VLA 15GHz polarization observations.
Why Is the “Time Delay Controversy In Q0957+561 Not Yet Decided”?
Authors: Oknyanskij V.L.
Published: July 2016

The time delay in Q0957+561 remains indeterminate due to differences between statistical methods, irregular data spacings, and (possibly) microlensing.
Structure Formation: Models, Dynamics And Status
Authors: Padmanabhan T.
Published: July 2016

All the popular models for structure formation are based on three key ingredients: (a) a model for the background universe (b) some mechanism for generating small perturbations in the early universe and (c) specification of the nature of the dark matter.
A 71 Megapixel Mosaic Camera For Weak Lensing At APO
Authors: Diercks A. , Stubbs C. , Hogan C. , Adelberger E.
Published: July 2016

We are developing a wide-field CCD camera system which is optimized for using weak gravitational lensing to study the distribution of dark matter in clusters of galaxies and eventually the field. The system will be used at the Apache Point Observatory (APO) 3.5 meter telescope in New Mexico.
Exponential Growth of Distance between Nearby Rays Due to Multiple Gravitational Lensing
Authors: Fukushige T. , Makino J.
Published: July 2016

We have investigated multiple gravitational lensing by numerical “ray tracing” simulations. We have found that the distance between rays grows exponentially, on average, until it reaches the projected mean separation of lensing objects (∼ RV–1/2, where R is the system size and N is the number of scattering object). This nature may affect observations of high redshift objects or the anisotropy of the cosmic background radiation.
Effect of Multiple Gravitational Lensing on the Anisotropy of the Cosmic Background Radiation
Authors: Fukushige T. , Makino J. , Ebisuzaki T.
Published: July 2016

We investigated smoothing of the cosmic background radiation (CBR) by multiple gravitational lensing. The CBR is gravitationally scattered by galaxies, clusters of galaxies, and superclusters during the travel from the last scattering surface. Although the effect of the gravitational lensing was thought to be unimportant, we found that the multiple gravitational lensing by clusters of galaxies or by superclusters can reduced by a large factor. This result is explained by the fact that the distance between two light rays grows exponentially though multiple gravitational lensing. If such structures were formed at z = 2–5 and contain a large fraction of the mass of the universe (Ωs > 0.5), then multiple gravitational lensing can reduce the temperature anisotropy of the CBR by 40-60%, approximately up to a degree scale.
A Multi-Wavelength Analysis Of The Matter Distribution In Clusters of Galaxies
Authors: Liang Haida
Published: July 2016

We combine the X-ray data and the Sunyaev-Zel'dovich effect with the constraints from gravitational lensing for an intermediate redshift cluster to check the consistency of various mass estimates and the validity of the assumption of hydrostatic equilibrium, and to deduce the properties of the intra-cluster gas, the profile of the cluster potential and Ho.
Gravitational Lenses and the Structure of Galaxies
Authors: Kochanek Christopher S.
Published: July 2016

Nearly singular isothermal mass distributions with small core radii are consistent with stellar dynamics, lens statistics, and lens models as a model for E/S0 galaxies. Models like the de Vaucouleurs model with a constant mass-to-light ratio are not. While the isothermal distributions are probably an oversimplification, E/S0 galaxies (at least in projection) must have significant amounts of dark matter on scales of an effective radius.
Microlensing With Binaries And Planets
Authors: Witt H.J. , Mao S.
Published: July 2016

The ongoing microlensing experiments have now discovered more than 70 candidate events (Alcock et al. 1993, Bennett et al. 1994, Aubourg et al. 1993, Udalski et al. 1994). These experiments have put important constraints on the dark matter content of the Galactic halo (Alcock et al. 1995a) and yielded many interesting results about Galactic structure (Paczyński et al. 1994, Stanek et al. 1994).
A Possible Manifestation Of Microlensing In Pulsar Timing
Authors: Larchenkova T.I. , Doroshenko O.V.
Published: July 2016

Gravitational lensing and the time delay of a pulsar signal in the gravitational field of a mass are General Relativistic effects that may be used as a tool to detect the observational parameters of dark matter in our Galaxy. We propose to use observations of the time delay of pulses from pulsars to detect lensing objects located close to the line of the sight, to study the distribution of dark matter in our Galaxy. We discuss the possibility of finding such an event by measuring the delay of pulses from a pulsar, and apply it to data for PSR B0525+21.
Microlensing Induced Spectral Variability In Q2237+0305
Authors: Lewis Geraint F. , Irwin Mike J. , Hewett Paul C.
Published: July 2016

The degree of microlensing induced amplification is dependent upon the size of a source. As quasar spectra consist of the sum of emission from different regions this scale dependent amplification can produce spectral differences between the images of a macrolensed quasar. This paper presents the first direct spectroscopic evidence for this effect, providing a limit on the scale of the continuum and the broad line emission regions at the center of a source quasar (2237+0305). Lack of centroid and profile differences in the emission lines indicate that substructure in the broad emission line region is > 0.05 parsecs.
The Microlensing Events In Q2237+0305A: No Case Against Small Masses/Large Sources
Authors: Haugan Stein Vidar Hagfors
Published: July 2016

Witt & Mao (1994) claim that the data reported by Racine (1992) contains “a quite well sampled M-shaped double event in image A of 0.3 and 0.4 mag, respectively”. They further state that the very low average mass scenario put forward by Refsdal & Stabell (1991) does not predict “well-resolved asymmetric events, as have been observed in image A”.
A Cusp—Counting Formula For Caustics Due To Multiplane Gravitational Lensing
Authors: Petters A. O.
Published: July 2016

Consider a gravitational lens system with K planes. If light rays are traced back from the observer to the light source plane, then the points on the first lens plane where a light ray either terminates, or, passes through and terminates before reaching the light source plane, are “obstruction points.” More precisely, tracing rays back to the source plane induces a K-plane lensing map η : U ⊆ R2 → R2 of the form η(x1) = x1 −∑i=1k αi(xi(xi)). We then define an obstruction point of η to be a point a of U where limx1→a |αi(xi(x1))| = ∞ for some “deflection angle” αi.
Microlensing Of Large Sources Including Shear Term Effects
Authors: Refsdal S. , Stabell R.
Published: July 2016

We find that the standard deviation for the observed magnitude of a large microlensed source is δm ≤ 2.17|κ|1/2θ∘/θs even in the presence of non-zero shear.
The Evolution of QSO Spectra: Evidence for Microlensing?
Authors: Francis Paul J. , Koratkar Anuradha
Published: July 2016

We find that the spectra of QSOs evolve: high redshift QSOs (z > 1.5) have lower equivalent width emission lines than low redshift QSOs (z < 0.5) with the same luminosities and radio properties.

We propose that microlensing by compact objects may account for the apparent evolution. If Ω ∼ 0.05 in compact objects, the continuum emission from many high redshift QSOs will be amplified, but not the line emission, leading to the observed decrease in the apparent equivalent widths.
UV/Optical Continuum Variability In AGNs
Authors: Sun Wei-Hsin , Heisler Charlene A. , Malkan Matthew A.
Published: July 2016

The observed strong UV/Optical excess in many Seyfert 1 galactic nuclei and quasars (QSOs) is well described as thermal radiation from the surface of an optically thick accretion disk surrounding a supermassive black hole (Malkan 1983, Sun and Malkan 1989). This scenario naturally leads to a radially symmetric temperature gradient with the innermost regions the hottest. Thus for a perturbation generated in the inner regions propagating outward, sequential variations from higher to lower frequencies should be expected, aside from the bolometric increase of brightness. However, the extremely intensive International AGN watch (Peterson 1993 and references therein) on NGC 5548 and UV/Optical monitoring campaign on Mkn 335 (Sun et al. 1995) point to opposite conclusions on the time lag between UV and Optical continua, with no lag for NGC 5548 and ∼ 50 days for Mkn 335. We thus began two monitoring programs at Lick Observatory and Mount Stromlo and Siding Spring Observatory (MSSSO) on a sample of Seyfert 1 galaxies with CCD direct imaging to search for more conclusive evidence on the sequential variabilities.
Identifying Optical Einstein Rings
Authors: Warren S. J. , Hewett P. C. , Lewis G. F. , Møller P. , Iovino A. , Shaver P. A.
Published: July 2016

The discovery of gravitationally lensed radio-rings (Hewitt et al. 1988) opened up a new line of attack on the problem of dark matter in galaxies. High–resolution radio observations (Langston et al. 1989) resolve structure tangentially and radially within the rings, providing sophisticated analysis routines (Kochanek & Narayan 1992, Wallington, Narayan & Kochanek 1994) with enough constraints to compute realistic models of the mass distribution within the deflectors (Kochanek 1995). Five such systems are now known and extensive programs to identify further examples are underway.
J03.13 A & B: A New Multiply Imaged QSO Candidate
Authors: Claeskens J.F. , Surdej J. , Remy M.
Published: July 2016

We report the discovery of a new gravitational lens (GL) candidate for the quasar J03.13 (z = 2.55). The mean angular separation and magnitude difference between the A & B QSO images are found to be 0.84″ and 2.10 mag, respectively. A spatially unresolved medium resolution spectrum of J03.13 shows intervening absorption line systems at z = 2.34 and z = 1.085. The latter one is possibly associated with a σ = 206 km/s lens galaxy.
Pixel Lensing: The Key to the Universe
Authors: Gould Andrew
Published: July 2016

Pixel lensing, the gravitational microlensing of unresolved stars, is potentially a powerful method for detecting and measuring microlensing events. Two groups are currently refining this method in observations toward M31. I show that the technique has wide application, from searching for intra-cluster Machos in the Virgo cluster, to improving the accuracy of follow-up observations of Galactic microlensing events, to measuring the star-formation history of the universe. I derive the equation for the pixel lensing event rate where Qmin is the minimum signal to noise for detection, τ is the optical depth, Nres is the number of telescope resolution elements in the field, is the photon detection rate from a fluctuation magnitude star, and ξ is a suppression factor.
The Parkes Lens Survey
Authors: Webster R. L. , Francis P. J. , Holman B. A. , Masci F. J. , Drinkwater M. J. , Peterson B. A.
Published: July 2016

We are undertaking an extensive survey of a sample of radio-selected flat-spectrum sources, which are predominantly quasars. The sample will be used for a range of gravitational lensing studies as well as studies of the generic properties of radio quasars. As yet we have not found any instances of multiply-imaged quasars, however we have found evidence for dust which we believe is reddening the observed spectra of many of the quasars. Samples which are selected to be complete in the radio are the best way to account for the effects of dust.
The ‘Gravitational Lensing’ Bibliography
Authors: Pospieszalska-Surdej A. , Surdej J. , Veron P.
Published: July 2016

We present a non-exhaustive bibliography on “Gravitational Lensing” (GL), totalizing nearly 1500 titles (see Pospieszalska-Surdej et al. 1993 for an earlier version of this bibliography). It also includes recent abstracts of papers dealing with gravitational lensing and submitted to astro-ph@babbage.sissa.it. The GL bibliography is accessible through a World-Wide-Web page at the URL (cf. next page) http://www.stsci.edu/ftp/stsci/library/grav_lens/grav_lens.html It is also possible to retrieve -via FTP- the latex file ‘grav_bib1.tex’ or the postscript file ‘grav_bib1.ps’ containing the most recent version of this bibliography. Please proceed as follows: ftp stsci.edu, Name: anonymous, Password: your E-mail address, cd stsci/library/grav_lens, get grav_bib1.tex or get grav_bib1.ps, and finally bye).

We are aware that the present compilation is not complete, not always uniform and that there are still errors, typos, etc. We would appreciate very much if you could communicate to us (via E-mail: surdej@stsci.edu) missing or new titles (published or accepted for publication), errors, changes and suggestions. It would also be nice for us to receive in the future your preprints or reprints related to ‘Gravitational Lensing’ studies. Please send your material to: A. Pospieszalska-Surdej, STScI, 3700 San Martin Drive, Baltimore MD 21218, USA.
Assembling Spiral Galaxies
Authors: Kennicutt R.C.
Published: July 2016

Nearby spiral galaxies offer vital clues to some of the most fundamental questions about galaxy formation and evolution: What is the star formation history of the universe, past and future? When did disks form, during the final stages of a single primeval collapse, or as a continuous or episodic process? What is the evolutionary nature of the Hubble sequence, and what are the physical mechanisms that dictate the present-day Hubble type of a galaxy? Was Hubble type imprinted at birth, or can it be deterined or at least modified by infall, mergers, or secular dynamical evolution within the galaxy? These issues are not specific to spirals, of course, and much of this conference will address just these questions in a broader context. However present-day spirals offer unique advantages for studying these problems; they exhibit a broad range of dynamical and evolutionary properties, and the dynamical fragility of disks makes them excellent seismometers of galaxy interaction and merger rates at recent epochs.
Finding Ages for Old Stellar Populations
Authors: Worthey Guy
Published: July 2016

We are far from being able to populate a histogram of star formation versus time for an elliptical galaxy based solely on observations of its spectrum, but the path toward such a dream is becoming more clear. Still, we are denied the easiest paths, and most of what I have been thinking about in the last six months are the obstacles rather than the opportunities in age determinations for old stellar populations, and Es in particular. The following list should illustrate what I mean.
The X-ray emission of E and S0 Galaxies
Authors: Fabbiano G.
Published: July 2016

It is well known by now that E and S0 galaxies are associated with hot, X-ray emitting gaseous halos, subject to central cooling flows, but otherwise homogeneous, which can be used to trace the galaxy potential and thus measure the total gravitational mass. Recent ASCA observations suggest that these halos have a surprisingly low metal abundance.
Interaction of Disks and Dark Haloes of Dwarf Spirals
Authors: Fuchs B. , Friese V. , Reffert H. , Wielen R.
Published: July 2016

In a number of dwarf spiral galaxies the HI-emission has been studied with sufficient resolution to derive the rotation curves of the galaxies. These show that the disks of dwarf spirals are imbedded in extended haloes of dark matter, quite similar to the disks of giant spiral galaxies.
The Structure of Dark Matter Halos in Dwarf Galaxies
Authors: Burkert A.
Published: July 2016

Some dwarf galaxies have HI rotation curves that are completely dominated by a surrounding dark matter (DM) halo (e.g. Carignan & Freeman 1988). These objects represent ideal candidates for an investigation of the density structure of low-mass DM halos as the uncertainties resulting from the subtraction of the visible component are small, even in the innermost regions. Flores & Primack (1994) and Moore (1994) compared the observed DM rotation curves with the profiles, predicted from cosmological cold dark matter (CDM) calculations. They found an interesting discrepancy: whereas the calculations lead to a DM density distribution which diverges as ρ ∼ r−1 in the inner parts, the observed rotation curves indicate shallow DM cores which can be described by an isothermal density profile with finite central density.
Caught in the Act: the identification of the galaxies responsible for the faint blue excess
Authors: Driver Simon P. , Windhorst Rogier A. , Griffiths Richard E.
Published: July 2016

We summarise recent Hubble Space Telescope results on the morphology of faint field galaxies. Our two principle results are: (1) the galaxies responsible for the faint blue excess have late-type/irregular morphology and (2) the number counts of normal galaxies, ellipticals and early-type spirals, are well fit by standard no-evolution models implying that the giant population was in place and mature by a redshift of ≥ 0.7.
Galaxy Formation and Evolution: What to Expect from Hierarchical Clustering Models
Authors: Frenk C.S. , Baugh C.M. , Cole S.
Published: July 2016

In hierarchical clustering theories of galaxy formation, galaxies form by gas cooling and condensing into dark matter halos which, in turn, form by a hierarchy of mergers (White & Rees 1978). The context in which this process takes place is specified by a cosmological model that determines the spectrum of primordial density fluctuations and the rate at which they grow by gravitational instability. The best known example of such a model is the cold dark matter (CDM) model (see Frenk 1991 for a review), but a number of alternatives (mostly variants of CDM), have recently become popular in response to new data on large-scale structure and the COBE detection of anisotropies in the microwave background radiation.
The Ecology of Quasar Absorption Systems
Authors: Tytler David
Published: July 2016

Gas along the lines of sight to QSOs produces narrow absorption lines from ions of the most abundant elements: H, He, C, N, O, Si, S, Mg and Fe. Most lines have rest wavelengths of a few hundred Å but some have wavelengths λ ≥ 900 Å, sufficient that they can be redshifted into the optical. The absorbing gas is normally transparent, except for Lyman continuum absorption, and dust extinction at the highest columns, so we can see hundreds of gas clouds along a line of sight. We see more absorption from higher redshifts, because the universe was denser then and the absorbing “clouds” have roughly constant proper size.
Conference Summary: Glimpse of a New Future
Authors: Faber S. M.
Published: July 2016

Research on galaxy formation is about to be inundated with data from the distant Universe and from highly realistic model simulations. First glimpses from this and other work are already showing the need for new paradigms of galaxy formation.
Star Formation in a Magnitude Limited Sample of Interacting Galaxies
Authors: Bergvall Nils , Laurikainen Eija , Aalto Susanne , Johansson Lennart
Published: July 2016

We report on optical/near-IR spectroscopy and photometry of a magnitude limited sample of interacting pairs and merging galaxies and a control sample of apparently isolated galaxies (1,2). All observations were carried out at ESO, La Silla. When compared to the control sample, the interacting galaxies show only a moderate increase of star formation activity, in the central area typically a factor 2-3. Starburst activity seems to be very rare. Ongoing CO observations (Aalto, Horellou, Booth, Wiklind, Bergvall) indicate that these objects are not particularly rich in molecular gas. The interacting/merging galaxies have relatively high optical luminosities and high FIR luminosities and temperatures but these parameters are not correlated with other star formation signatures. We conclude that the interacting and merging galaxies in this sample, from the global star formation aspect, do not differ dramatically from scaled up versions of normal, isolated galaxies. This could suggest that many of the most lumino components in interacting pairs could originate from multiple ‘quiet’ mergers.
Supergiant Shells and Hot Gas in NGC 4449
Authors: Bomans D.J. , Chu Y.-H. , Hopp U.
Published: July 2016

Supergiant shells are the largest interstellar structures in galaxies. They are outlined by long H II filaments enclosing an inner space containing very little warm or cold gas. In the LMC, two supergiant shells have been detected in X-rays indicating the existence of hot gas: LMC 2 (Wang & Helfand 1992) and LMC 4 (Bomans et al. 1994). It is not yet clear whether the hot gas in a galactic halo is supplied by such supergiant shells.
Age-Metallicity Relation: Comparison of Open Clusters' Data with Stellar Populations
Authors: Carraro Giovanni , Ng Yuen K.
Published: July 2016

The age–metallicity relation (AMR) from the Old Open Clusters population (Carraro & Chiosi, 1994; Friel & Janes, 1993) is compared with the disc stellar populations obtained from a recently developed model of the Milky Way by Ng 1994. A picture for the chemical evolution of the disc is presented in which the presence of a newly discovered Bar population (t = 8–9 Gyr, Z = 0.005–0.030) is taken into account. We suggest that the past history of the Galactic Disc has been significantly influenced by infall of metal poor gas from the halo and accretion events. The results are shown in Fig. 1.
How Many ULIRGs are Mergers?
Authors: Clements D.L. , McMahon R.G. , Sutherland W.J. , Saunders W.
Published: July 2016

Ultraluminous IRAS Galaxies (ULIRGs) are unusual galaxies with luminosities > 1012L⊙ (H0 = 75 kms−1 Mpc−1), comparable to optically selected quasars, with up to 90% of this emitted in the 8-1000 μm region. Initial work on nearby ULIRGs suggested that all of these objects were in interacting or merging systems. Larger samples (e.g. Leech et al 1994) suggested that this might only be true for 2/3 of the objects. The triggering of ULIRG-type activity in the non-merging galaxies would then be difficult to understand.
Properties of low Surface Brightness Galaxies
Authors: de Blok W.J.G. , Van Der Hulst J.M. , McGaugh S.S.
Published: July 2016

We have been working on multiband surface photometry, spectrophotometry and Hi synthesis data for 20 Low Surface Brightness (LSB) galaxies. LSB galaxies are well described by disks with an average central surface brightness of ∼ 23.4B-mag arcsec–2. They have scale lengths typical for high surface brightness (HSB) galaxies, though a large range of sizes is present. Their colours are blue, especially at the red side of the spectrum, where they are significantly bluer than HSB galaxies (de Blok et al. 1995a). Modelling and measurements of gas abundances (McGaugh 1994) suggests a low, stochastic star formation rate, and a lack of a large old population. The Hi surface densities are a factor of three lower than those in HSB galaxies (de Blok et al 1995b). However the difference is not as large as in the optical. The Hi disks are considerably larger, relative to the optical disks, than in HSB galaxies. The gas mass fraction is higher, indicating slow evolution. Star formation is inhibited by the low surface densities which are typically below the critical treshold as stipulated by Toomre's gravitational instability criterion. The rotation curves rise gradually, and are observed to flatten out only in a few cases. Often they still rise at the last measured point, or remain solid body through-out. Preliminary mass models suggest extended low density dark matter halos, with baryon dominated inner regions. The inferred evolution for LSB galaxies shows mass and density are fundamental parameters in determining a galaxy's evolutionary fate.
Effects of Dust Extinction in Galactic Discs
Authors: Di Bartolomeo A. , Barbaro G. , Perinotto M.
Published: July 2016

We have solved the radiative transfer equation taking into account both absorption and scattering into the line of sight to the observer to model the disc of spiral galaxies.

A dust model has been adopted, suitable for the diffuse interstellar medium of our Galaxy, to obtain, in aU the considered spectral range (1000 ÷ 10000 Å), consistent quantities to describe both the absorption and the scattering properties of the dust.
Time Scales for Galaxy Formation and Intra-Cluster Medium Enrichment
Authors: Elbaz D. , Vigroux L.
Published: July 2016

Recent observations with ASCA (Mushotzky 94, New Horizon of X-Ray Astron.-1st Results from ASCA) have confirmed the prediction (Arnaud et al. 92, A&A 254, 49; Elbaz et al. 95, to appear in A&A) that the Fe present in the intra-cluster medium (ICM) is mainly due to SNII and not SNIa: α-elements (O, Ne, Si, S) are overabundant with respect to Fe. To account for the large Fe mass present in galaxy clusters as well as these abundances ratios, one must consider that the IMF was different in the past, favouring high-mass stars. Moreover, the simplest way to eject the enriched ISM into the ICM is to consider that the same high-mass stars that were responsible for the Fe enrichment have also driven a galactic wind in young E/SO's.
The Metal-Rich Disk Population
Authors: Feltzing Sofia , Gustafsson Bengt
Published: July 2016

Edvardson et al 1993 demonstrated that rapid build up of oxygen in the inner Galaxy. Do these high [O/Fe] ratios prevail also for metal rich stars? We have obtained high resolution (R = 100 000) spectra with the 2D-Coude Spectrometer at the McDonald Observatory 2.7 m telescope for 50 metal rich F, G and K dwarfs. These stars where chosen to represent both an old stellar population which originates ‘inside’ the solar orbit and the young extreme Population I.
Evolution of Galaxies Through Their Interactions
Authors: Funato Y. , Marino J.
Published: July 2016

We investigated how the encounters between galaxies change their mass M and velocity dispersion σ. We carried out a series of direct N-body simulation of encounters of two spherical galaxies. In Figure 1, the relative change of energy ΔE/E are plotted against that of mass ΔM/M for various initial conditions. The filled and open symbols correspond to the cases of Plummer model and relaxed Hernquist model, respectively. Here β ≡ (ΔE/E)/(ΔM/M).
A Supernova Remnant in the Dwarf HO IX
Authors: Hopp Ulrich , Zimmermann H.U. , Stickel Manfred , Henkel Christian
Published: July 2016

The dwarf irregular galaxy Ho IX (DDO 66) is a satellite of the giant spiral M81. Triggered by an interaction with M81 (Hopp & Schulte-Ladbeck, 1987 AA 187, 5), Ho IX may have recently undergone a burst of star formation. On very deep Calar Alto 3.5m telescope R images, we detected a ring-like nebula in the northeastern part of Ho IX, which is situated near to the giant CO molecular cloud recently discussed by Henkel et al. (1993 AA 273, L15). The structure of the nebula resembles supernova remnants like CTB 80. No HI-features can be detected at its location, especially no hole. It shows a blue central point source (R=21.7). A Lucy deconvolution of the 0.9″ seeing images indicates further faint point sources, perhaps a small stellar cluster. An optical long slit spectrum of the nebula shows emission lines with ratios as in old supernova remnants while it excludes normal HII regions, planetary nebula, or the LMC X-1 type nebula. The position of the central object coincides with a bright and variable ROSAT point source which was already detected by the Einstein spacecraft. The X-ray spectrum is rather steep and shows strong intrinsic absorption. The nature of the X-ray source and its possible connection to the optical nebula is not yet understood. Miller (1995, ApJ 446, L75) who independetly found the nebula interpretated his spectra as a supershell surrounding an OB association. Our optical nebula line ratios severely deviates from Miller's. Our ratios as the X-ray spectrum point more to a SNR at the M81 distance, most probably belonging to Ho IX.
The Overabundance of Magnesium over Iron in Bulges of Spiral Galaxies
Authors: Jablonka P. , Arimoto N. , Martin P.
Published: July 2016

We have collected integrated light spectra of bulges of 28 spiral galaxies. Our data sample the Hubble sequence uniformly from S0 to Sd types, and cover a large range in magnitude, viz, about −16 to −22 mag in r-Gunn band. In short, disks do not contribute to more than 14% of the total integrated light in our spectra, and all galaxies are analyzed under the same conditions. More to read in a forthcoming paper.
The Signatures of Galactic Disk Evolution in Vertical Colour Profiles of Edge-On Galaxies
Authors: Just A. , Fuchs B. , Wielen R. , Scorza C.
Published: July 2016

Galactic disks are heated by some gravitational scattering process. The velocity dispersion and scale height increases with the age of the stellar populations as can be observed directly in the solar neighbourhood. This evolutionary effect can also be derived from the vertical structure of spiral galaxies seen edge-on. We use a physical model of a selfgravitating disk composed of isothermal subpopulations with increasing age and velocity dispersion and an exponential dust distribution (Just et al. 1995). The emissivity of the stars is computed from the luminosities in the different bands of single age populations which are computed with the method of photometric evolutionary synthesis (Einsel et al. 1995).
Identifications of Faint IRAS Sources
Authors: Kümmel M.W. , Wagner S.J.
Published: July 2016

From overlapping scans in the IRAS all-sky survey and additional pointed observations the deepest far infrared survey before ISO exists in the region around the North Ecliptic Pole (NEP) (Hacking P. and Houck J.R., ApJS 63 p. 311). This survey contains detections up to 10 and fluxes up to 100 times fainter than the IRAS survey. In the central square degree around the NEP we combine the far IR-survey with deep radio data at 151 MHz and 1.5 GHz (Visser, A.E. et al., A&AS 110 p. 419, Kollgaard, R.I. et al., ApJS 93 p. 145) and own observation at 2.2μm (K′) and 435nm (B). The error circle around the IRAS source was chosen to include the true source with 85% probability (1.4 sigma). For 29 of the 32 IRAS sources we found at least one possible counterpart. Ten of the objects have multiple (up to four) counterparts in K′. Four of the IRAS sources have counterparts in the 1.5 GHz survey. The higher accuracy of the radio position (∼ 1″) allowed an unambiguous identification of the K′ counterpart. None of the IRAS sources could be found in the 151 MHz survey. The broad band spectra of the three galaxies with measured radio flux exhibit maximum emission between the radio band and 100μm which corresponds to emission by cool dust (< 50 K). Contrary to the infrared luminosity functions at 12μm and 60μm which show power laws, the K′ luminosity function is bimodal. The brightest K′ objects are all point sources. Due to the small number statistics the power law indices of the luminosity functions can not be distinguished. We find a linear relationship between the K′ flux and the flux at 60μm and 12μm over at least one decade. The large deviations by individual sources make an identification of the correct counterpart through this relation impossible. The spectral energy distributions of unambiguously identified sources span only one decade in energy (vSv), i.e. they have flat energy distributions. This suggests an identification of K′ objects with flat energy distribution in case of multiple counterparts.
Simulation of Mass Transport in Disk Galaxies
Authors: von Linden S. , Heidt J. , Reuter H.P. , Wielebinski R.
Published: July 2016

The large-scale dynamics and evolution of disk galaxies is controlled by the angular-momentum transport provided by non-axisymmetric perturbances through their gravity torques. To continuously maintain such gravitational instabilities, the presence of the gas component and its dissipative character are essential.