pinecone/core-2020-05-10-deduplication huggingface dataset:
Secular evolution of galaxy morphologies

Today we have numerous evidences that spirals evolve dynamically through various secular or episodic processes, such as bar formation and destruction, bulge growth and mergers, sometimes over much shorter periods than the standard galaxy age of 10-15 Gyr. This, coupled to the known properties of the Hubble sequence, leads to a unique sense of evolution: from Sm to Sa. Linking this to the known mass components provides new indications on the nature of dark matter in galaxies. The existence of large amounts of yet undetected dark gas appears as the most natural option. Bounds on the amount of dark stars can be given since their formation is mostly irreversible and requires obviously a same amount of gas
mm observations of IRAS galaxies: dust properties, luminosity functions and contributions to the sub-mm background

We have studied the FIR/{\it mm} spectrum of IR galaxies by combining IRAS photometry with new {\it mm} data on a complete southern IRAS galaxy sample. The observed spectra and a dust model emphasize a dicothomy in the galaxy population: half of the objects with a lot of warm dust are characterized by higher values of the bolometric (UV-FIR) luminosity, of the dust-to-gas mass ratio, of the dust optical depths and extinction, while those dominated by cold ({\it cirrus}) dust show opposite trends. From these data we derive the {\it mm} luminosity function of galaxies and estimate their contribution to the sub-{\it mm} background (BKG)
Mapping the cold dust in edge-on galaxies at 1.2 mm wavelength

Using the IRAM 30-m telescope, we have mapped the 1.2mm continuum emission in NGC 891, NGC 5907 and NGC 4565. In particular this latter galaxy shows a weak, extended plateau that is correlated with HI in addition to the central peak and ring structure common to all these spirals. Moreover, the outer part of this dust emission of NGC 4565 is clearly warped. The average dust temperature in the outer parts is 15 K and the derived dust absorption cross section is very close to that predicted for the local diffuse clouds
The distribution of dust and gas in elliptical galaxies

Results from IRAS and recent optical CCD surveys are examined to discuss the distribution and origin of dust and ionized gas in elliptical galaxies. In strong contrast with the situation among spiral galaxies, masses of dust in elliptical galaxies as derived from optical extinction are an order of magnitude LOWER than those derived from IRAS data. I find that this dilemma can be resolved by assuming the presence of a diffusely distributed component of dust which is not detectable in optical data. The morphology of dust lanes and their association with ionized gas in elliptical galaxies argues for an external origin of BOTH components of the ISM
Very cold gas and dark matter

We have recently proposed a new candidate for baryonic dark matter: very cold molecular gas, in near-isothermal equilibrium with the cosmic background radiation at 2.73 K. The cold gas, of quasi-primordial abundances, is condensed in a fractal structure, resembling the hierarchical structure of the detected interstellar medium. We present some perspectives of detecting this very cold gas, either directly or indirectly. The H_2 molecule has an "ultrafine" structure, due to the interaction between the rotation-induced magnetic moment and the nuclear spins. But the lines fall in the km domain, and are very weak. The best opportunity might be the UV absorption of H_2 in front of quasars. The unexpected cold dust component, revealed by the COBE/FIRAS submillimetric results, could also be due to this very cold H_2 gas, through collision-induced radiation, or solid H_2 grains or snowflakes. The \gamma-ray distribution, much more radially extended than the supernovae at the origin of cosmic rays acceleration, also points towards and extended gas distribution
Influence of chromophores on quarternary structure of phycobiliproteins from the cyanobacterium, Mastigocladus laminosus

Chromophores of C-phycocyanin and phycoerythrο-cyanin have been chemically modified by reduction to
rubins , bleaching , photoisomerization , or perturbation
with bulky substituents. Pigments containing modified
chromophores, or hybrids containing modified and unmodified chromophores in individual protomers have been prepared. All modifications inhibit the association of the
(aß)-protomers of these pigments to higher aggregates. The
results demonstrate a pronounced effect of the state of
the chromophores on biliprotein quaternary structure. It
may be important in phycobi1isome assembly , and also in
the dual function of biliproteins as (i) antenna pigments
for photosynthesis and (ii) reaction centers for photomor-phogenesis.
19th Century mechanical models of eye movements, Donders’ law, Listing’s law and Helmholtz’ direction circles

Donders, Ruete, von Graefe, von Helmholtz, Listing, Volkmann and many others have provided the broad outline of an answer to the question how the eye rotates during eye movements. Many mechanical models of eye movements, ophthalmotropes, have been constructed and studied in the nineteenth century. These models have primarily served to explain Donders’ and Listing’s Laws on the nature of eye movements. As both Donders’ Law and Listing’s Law are easier to understand when seen against the background of the coordinate systems used to describe eye movements, all of the coordinate systems currently in use in the diagnosis and treatment of strabismus are described. In addition, the reader is introduced to a coordinate system based on von Helmholtz’ direction circles, circles describing the direction of the horizontal and vertical retinal meridians in all positions of gaze
Hierarchical Systems in Open Clusters

In this paper we study the formation, evolution and disruption of hierarchical systems in open clusters. With this purpose, N-body simulations of star clusters containing an initial population of binaries have been carried out using Aarseth's NBODY4 and NBODY5 codes. Stable triples may form from strong interactions of two binaries in which the widest pair is disrupted. The most frequent type of hierarchical systems found in the cluster models are triples in which the outer star is single, but in some cases the outer body is also a binary, giving a hierarchical quadruple. Many triple systems are non-coplanar and the presence of even a very distant and small outer companion may affect the orbital parameters of the inner binary, including a possible mechanism of significant shrinkage if the binary experiences a weak tidal dissipation. The main features of these systems are analyzed in order to derive general properties which can be checked by observations. The formation of exotic objects, such as blue stragglers and white dwarf binaries, inside hierarchical triple systems is particularly interesting
Warm gas at high redshift: clues to gravitational structure formation from optical spectroscopy of Lyman $\alpha$ absorption systems

We discuss the effects of gravitational collapse on the shape of absorption line profiles for low column density (log N(HI) < 14) Lyman Alpha forest clouds and argue by comparison with cosmological simulations that Lyman alpha forest observations show the signs of ongoing gravitational structure formation at high redshift. The departures of observed line profiles from thermal Voigt profiles (caused by bulk motion of infalling gas and compressional heating) are evident from the results of profile fitting as a correlation in velocity space among pairs of components with discrepant Doppler parameters. This correlation also allows us to qualitatively understand the meaning of the Doppler parameter - column density (b vs. N(HI)) diagram for intergalactic gas
A radio search for high redshift HI absorption

Ground based optical observations have yielded considerable information on the statistics of damped-lyman alpha systems. In particular these systems are known to be the dominant repository of the observed neutral gas at high redshift. However, particularly at high redshift, there is the possibility that optical observations could be biased due to the exclusion of damped-lyman alpha systems that contain moderate to significant amounts of dust. Independent observational constraints on the neutral hydrogen content at high redshifts and the amount of dust in high redshift systems can be obtained from a radio search against the bright lobes of distant radio galaxies (which is less affected by the presence of dust in foreground damped-lyman alpha systems). We describe here a pilot radio survey along the line of sight to a small sample of high redshift radio galaxies, and also present some preliminary results. The survey uses a novel observing mode at the WSRT which enables one to make sensitive searches of a large redshift interval in a modest amount of telescope time
The european large area ISO survey: elais

I describe a European collaborative project to survey \sim 20 square degrees of the sky at 15\micron and 90\micron with ISO. This is the largest open time project being undertaken by ISO. The depth and areal coverage were designed to complement the various Guaranteed Time surveys. The main science thrust is to explore star formation in galaxies to a much higher redshift than was probed by IRAS. We expect to detect around 8000 extra-galactic objects and a similar number of Galactic sources. The maps and source catalogues will represent a major legacy from ISO, inspiring follow up work for many years to come
Small scale structure and high redshift HI

Cosmological simulations with gas dynamics suggest that the Lyman-alpha forest is produced mainly by "small scale structure" --- filaments and sheets that are the high redshift analog of today's galaxy superclusters. There is no sharp distinction between Lyman-alpha clouds and "Gunn-Peterson" absorption produced by the fluctuating IGM -- the Lyman-alpha forest {\it is} the Gunn-Peterson effect. Lyman limit and damped Lyman-alpha absorption arises in the radiatively cooled gas of forming galaxies. At z~2-3, most of the gas is in the photoionized, diffuse medium associated with the Lyman-alpha forest, but most of the {\it neutral} gas is in damped Lyman-alpha systems. We discuss generic evolution of cosmic gas in a hierarchical scenario of structure formation, with particular attention to the prospects for detecting 21cm emission from high redshift HI. A scaling argument based on the present-day cluster mass function suggests that objects with M_{HI} >~ 5e11 h^{-1} \msun should be extremely rare at z~3, so detections with existing instruments will be difficult. An instrument like the proposed Square Kilometer Array could detect individual damped Lyman-alpha systems at high redshift, making it possible to map structure in the high redshift universe in much the same way that today's galaxy redshift surveys map the local large scale structure
Hydrodynamical Simulations of the IGM at High Mach Numbers

We present a new approach to doing Eulerian computational fluid dynamics that is designed to work at high Mach numbers encountered in hydrodynamical simulations of the IGM. In conventional Eulerian CFD, the thermal energy is poorly tracked in supersonic bulk flows where local fluid variables cannot be accurately separated from the much larger bulk flow components. We described a method in which local fluid quantities can be directly tracked and the Eulerian fluid equations solved in a local frame moving with the flow. The new algorithm has been used to run large hydrodynamical simulations on a 1024^3 grid to study the kinetic SZ effect. The KSZ power spectrum is broadly peaked at l~10^4 with temperature fluctuations on micro Kelvin levels
A Chandra and XMM View of the Mass & Metals in Galaxy Groups and Clusters

X-ray observations with Chandra and XMM are providing valuable new measurements of the baryonic and dark matter content of groups and clusters. Masses of cD clusters obtained from X-ray and gravitational lensing studies generally show good agreement, therefore providing important validation of both methods. Gas fractions have been obtained for several clusters that verify previous results for a low matter density (Omega_m ~0.3). Chandra has also provided measurements of the mass profiles deep down into several cluster cores and has generally found no significant deviations from CDM predictions in contrast to the flat core density profiles inferred from the rotation curves of low-surface brightness galaxies and dwarf galaxies; i.e., there is no evidence for self-interacting dark matter in cluster cores. Finally, initial studies of the iron and silicon abundances in centrally E-dominated groups show that they have pronounced gradients from 1-2 solar values within the central 30-50 kpc that fall to values of 0.3-0.5 solar at larger radii. The Si/Fe ratios are consistent with approximately 80% of the metals originating from Type Ia supernovae. Several cD clusters also display central Fe enhancements suggestive of Type Ia supernova enrichment, though some have central dips that may provide a vital clue for solving the cooling flow mystery
X-Ray IGM in the Local Group

Recent observations with the dispersive X-ray spectrometers aboard Chandra and Newton Observatory have begun to probe the properties of the X-ray intergalactic medium (IGM) at small redshifts. Using large quantities (~950 ksec) of spectroscopic data acquired using the RGS aboard Newton Observatory, we investigated the intervening material toward three low redshift, high Galactic latitude AGNs with nominally featureless spectra: Mrk421, PKS2155-304 and 3C273. Each spectrum provides clear evidence for what appears to be a local (z~0), highly ionized absorbing medium betrayed by the OVII 1s-2p resonance transition feature seen at 21.6A (N[OVII] ~ 1E16 cm-2). Measurements are also made for the Lyman alpha transition of the adjacent ionization state, (OVIII; 18.97A), which potentially constrains the absorber's temperature. Finally, in a collisional equilibrium approximation, upper limits to diffuse emission intensities place upper limits on the electron density (ne < 2E-4 cm-3), lower limits on the scale length of the absorber (L > 140 kpc) and lower limits on its mass (M > 5E10 M[sun]). Limits on the absorber's scale length and its velocity distribution lead us to identify it with the Local Group
Mg II & C IV Kinematics vs. Stellar Kinematics in Galaxies

Comparisons of the kinematics of Mg II absorbing gas and the stellar rotation curves in 0.5 < z < 1.0 spiral galaxies suggests that, at least in some cases, the extended gaseous envelopes may be dynamically coupled to the stellar matter. A strong correlation exists between the overall kinematic spread of Mg II absorbing gas and C IV absorption strength, and therefore kinematics of the higher-ionization gas. Taken together, the data may suggest a "halo/disk connection" between z~1 galaxies and their extended gaseous envelopes. Though the number of galaxies in our sample are few, there are no clear examples that suggest the gas is accreting/infalling isotropically about the galaxies from the intergalactic medium
The FUSE survey of OVI absorption in and near the Galaxy

We present FUSE observations of OVI absorption in a sample of 100 extragalactic targets and 2 distant halo stars. We describe the details of the calibration, alignment in velocity, continuum fitting, and manner in which contaminants were removed (Galactic H2, absorption intrinsic to the background target and intergalactic Ly-beta lines). We searched for OVI absorption in the velocity range -1200 to 1200 km/s. With a few exceptions, we only find OVI between -400 and 400 km/s; the exceptions may be intergalactic OVI. We discuss the separation of the observed OVI absorption into components associated with the Galactic halo and components at high-velocity, which are probably located in the neighborhood of the Galaxy. We describe the measurements of equivalent width and column density, and we analyze the different contributions to the errors. We conclude that low-velocity Galactic OVI absorption occurs along all sightlines - the few non-detections only occur in noisy spectra. We further show that high-velocity OVI is very common, having equivalent width >65 mAA in 50% of the sightlines and >30 mAA in 70% of the high-quality sightlines. The high-velocity OVI absorption has velocities relative to the LSR of +/-(100--330) km/s; there is no correlation between velocity and absorption strength. We present 50 km/s wide OVI channel maps. These show evidence for the imprint of Galactic rotation. They also highlight two known HI high-velocity clouds (complex~C and the Magellanic Stream). The channel maps further show that OVI at velocities <-200 km/s occurs along all sightlines in the region l=20-150, b<-30, while OVI at velocities >200 km/s occurs along all sightlines in the region l=180-300, b>20 (abbreviated)
How Do Galaxies Get Their Gas?

Not the way one might have thought. In hydrodynamic simulations of galaxy formation, some gas follows the traditionally envisioned route, shock heating to the halo virial temperature before cooling to the much lower temperature of the neutral ISM. But most gas enters galaxies without ever heating close to the virial temperature, gaining thermal energy from weak shocks and adiabatic compression, and radiating it just as quickly. This ``cold mode'' accretion is channeled along filaments, while the conventional, ``hot mode'' accretion is quasi-spherical. Cold mode accretion dominates high redshift growth by a substantial factor, while at z<1 the overall accretion rate declines and hot mode accretion has greater relative importance. The decline of the cosmic star formation rate at low z is driven largely by geometry, as the typical cross section of filaments begins to exceed that of the galaxies at their intersections
Galactic Recycling: The HI Ring Around NGC 1533

We report the discovery of a new HI ring around the S0 galaxy NGC 1533. The ring orbits at a radius of 35 kpc, well outside the optical extent of the galaxy. We have conducted N-body/SPH numerical simulations to show this HI ring could be the merger remnant of a tidally destroyed galaxy. We find no optical component associated with the HI ring. However, observations hint at H-alpha emission associated with the SE part of the ring only. The H-alpha is in the form of a few very small isolated emission line regions. The large HI velocity dispersions (up to 30 km/s) and velocity gradients (up to 50 km/s/kpc) in this region indicate the H-alpha emission could be due to star formation triggered by clouds colliding within the ring
Line versus Flux Statistics -- Considerations for the Low Redshift Lyman-alpha Forest

The flux/transmission power spectrum has become a popular statistical tool in studies of the high redshift ($z > 2$) Lyman-alpha forest. At low redshifts, where the forest has thinned out into a series of well-isolated absorption lines, the motivation for flux statistics is less obvious. Here, we study the relative merits of flux versus line correlations, and derive a simple condition under which one is favored over the other on purely statistical grounds. Systematic errors probably play an important role in this discussion, and they are outlined as well
Where has all the neutral hydrogen gone?

Our extremely deep survey for extragalactic HI (HIDEEP) finds no intergalactic gas clouds, and no galaxies with HI at inferred global column-densities below 10^20 cm^-2 when we could have detected such objects down to a completeness limit of 4 x 10^18 cm^-2. We speculate that low surface-density hydrogen is either ionised or locked up in ``frozen discs'', i.e. structures where the local Ly-alpha is insufficient to excite the 21-cm transition to a spin-temperature above the cosmic background. Such ``frozen discs'' might be responsible for many QSOALSs
Simulating the Hot X-ray Emitting Gas in Elliptical Galaxies

We study the chemo-dynamical evolution of elliptical galaxies and their hot X-ray emitting gas using high-resolution cosmological simulations. Our Tree N-body/SPH code includes a self-consistent treatment of radiative cooling, star formation, supernovae feedback, and chemical enrichment. We present a series of LCDM cosmological simulations which trace the spatial and temporal evolution of heavy element abundance patterns in both the stellar and gas components of galaxies. X-ray spectra of the hot gas are constructed via the use of the vmekal plasma model, and analysed using XSPEC with the XMM EPN response function. Simulation end-products are quantitatively compared with the observational data in both the X-ray and optical regime. We find that radiative cooling is important to interpret the observed X-ray luminosity, temperature, and metallicity of the interstellar medium of elliptical galaxies. However, this cooled gas also leads to excessive star formation at low redshift, and therefore results in underlying galactic stellar populations which are too blue with respect to observations
Effects of Noise on Galaxy Isophotes

The study of shapes of the images of objects is an important issue not only because it reveals its dynamical state but also it helps to understand the object's evolutionary history. We discuss a new technique in cosmological image analysis which is based on a set of non-parametric shape descriptors known as the Minkowski Functionals (MFs). These functionals are extremely versatile and under some conditions give a complete description of the geometrical properties of objects. We believe that MFs could be a useful tool to extract information about the shapes of galaxies, clusters of galaxies and superclusters. The information revealed by MFs can be utilized along with the knowledge obtained from currently popular methods and thus could improve our understanding of the true shapes of cosmological objects
Three aspects of red giant studies in the Magellanic Clouds

There are three important aspects concerning the study of the red giant and in particular of the asymptotic giant branch (AGB) stars in the Magellanic Clouds. These are: the surface distribution, the luminosity function and the variability. The spatial distribution of AGB stars is an efficient tool to study the structure of the galaxies and their metalicity by analysing the ratio between carbon- and oxygen-rich AGB stars. The shape of the luminosity function carries informations about the star formation rate in the Clouds and it can be mathematically related to their history. Most AGB stars vary their magnitude in a few to several hundred years time; the one epoch DENIS magnitudes for both Large and Small Magellanic Cloud AGB stars outline the same relations as a function of period
Luminosities of AGB Variables

The prevailing evidence suggests that most large-amplitude AGB variables follow the period luminosity (PL) relation that has been established for Miras in the LMC and galactic globular clusters. Hipparcos observations indicate that most Miras in the solar neighbourhood are consistent with such a relation. There are two groups of stars with luminosities that are apparently greater than the PL relation would predict: (1) in the LMC and SMC there are large amplitude variables, with long periods, P> 420 days, which are probably undergoing hot bottom burning, but which are very clearly more luminous than the PL relation (these are visually bright and are likely to be among the first stars discovered in more distant intermediate age populations); (2) in the solar neighbourhood there are short period, P<235 days, red stars which are probably more luminous than the PL relation. Similar short-period red stars, with high luminosities, have not been identified in the Magellanic Clouds