Showing papers on "Galaxy merger published in 1988"
TL;DR: In this paper, the CO luminosities of 93 galaxies have been determined and compared with their IRAS FIR luminosity, showing that the high ratio of FIR/L(CO) in strongly interacting galaxies is due to star formation, while the efficiency of this process is higher than that of any galactic GMC.
Abstract: The CO luminosities of 93 galaxies have been determined and are compared with their IRAS FIR luminosities. Strongly interacting/merging galaxies have L(FIR)/L(CO) substantially higher than that of isolated galaxies or galactic giant molecular clouds (GMCs). Galaxies with tidal tails/bridges are the most extreme type with L(FIR)/L(CO) nine times as high as isolated galaxies. Interactions between close pairs of galaxies do not have much effect on the molecular content and global star-formation rate. If the high ratio L(FIR)/L(CO) in strongly interacting galaxies is due to star formation then the efficiency of this process is higher than that of any galactic GMC. Isolated galaxies, distant pairs, and close pairs have an FIR/CO luminosity ratio which is within a factor of two of galactic GMCs with H II regions. The CO luminosities of FIR-luminous galaxies are among the highest observed for any spiral galaxies.
193 citations
TL;DR: In this article, a color-magnitude diagram was used to identify both normal galaxies with z = 0.3-1 and what appears to be a new distinct population, which has properties roughly similar to what would be expected for large galaxies at z greater than six undergoing a rapid luminous phase of star formation.
Abstract: Deep near-infrared imaging was obtained to study extragalactic populations, and a color-magnitude diagram was used to identify both normal galaxies with z = 0.3-1 and what appears to be a new distinct population. The latter has properties roughly similar to what would be expected for large galaxies at z greater than six undergoing a rapid luminous phase of star formation. It is suggested that these galaxies are good candidates for primeval galaxies. The normal galaxies identified are also important for studies of galaxy evolution, since they are found in the near-infrared, which is only weakly affected by evolution of the stellar populations. 17 references.
185 citations
TL;DR: In this article, the authors used the Kolmogorov-Smirnov test to test the effect of galaxy-galaxy interactions on the Butcher-Oemler effect at redshifts near 0.2.
Abstract: The spectra and images of 10 blue emission-line galaxies observed in Abell 963 (5), Abell 2111 (4), and Abell 2125 (1) are presented. A wide range in the spectral properties of the galaxies is found, yet the large majority of the galaxies has spectra which are consistent with very recent star formation. Only one of the 10 galaxies appears to contain an active nucleus. Since star formation is now occurring in these galaxies, residual effects from the triggering mechanism may still be apparent. Images of these emission-line galaxies show that several appear to be members of interacting systems. Others show evidence for possible interactions, either being somewhat morphologically disturbed or having disturbed neighbor galaxies. To test the idea of interactions, a nearest neighbor analysis on these emission-line galaxies and a sample of red galaxies was performed using the Kolmogorov-Smirnov test. The emission-line galaxies have closer neighbor galaxies than the red galaxy sample at greater than the 98 percent level of confidence. From this result and from the images themselves, it is concluded that galaxy-galaxy interactions can induce bursts of star formation and are an active agent of the Butcher-Oemler effect at redshifts near 0.2. These interactions may be the primarymore » cause of the B-O effect. 40 references.« less
143 citations
TL;DR: In this paper, the same empirical relationship between CO brightness and H2 surface mass density as has been found for giant molecular clouds in the Milky Way, was found for the UV-excess quasar Mrk 1014.
Abstract: Carbon dioxide (1 yields 0) emission has been detected from the UV-excess quasar Mrk 1014 (=PG 0157+001=IRAS 01572+0009) at z=0.163. Assuming the same empirical relationship between CO brightness and H2 surface mass density as has been found for giant molecular clouds in the Milky Way, the mass of H2 gas is approximately 4 x 10 to the 10th solar masses, i.e., more than ten times the H2 content of our Galaxy. The infrared and molecular gas properties of Mrk 1014 are similar to other warm, ultraluminous infrared galaxies such as Mrk 231, and IRAS 15206+3342 (z=0.125) from which CO(1 yields 0) emission is also reported. The trigger for the intense infrared activity in both Mrk 1014 and IRAS 15206+3342 appears to be a recent galaxy merger. It is suggested that objects such as these represent an important link in the evolution of ultraluminous infrared galaxies into UV-excess quasars.
47 citations
TL;DR: In this article, the formation and evolution of massive binary black holes in galactic nuclei were studied with respect to the loss-cone filling model for the fueling of massive black holes during the final stage of galaxy mergers, and a relation between the precession period of the jet and the fueling rate of the central hole was obtained.
Abstract: The formation and evolution of massive binary black holes in galactic nuclei are studied with respect to the loss-cone filling model for the fueling of massive black holes in AGN during the final stage of galaxy mergers. A relation between the precession period of the jet and the fueling rate of the central hole has been obtained. It is shown that the characteristic time for position angle variation may be correlated with the level of central activity. 48 references.
46 citations
Book•
01 Jan 1988TL;DR: This atlas contains photographs of 322 galaxies including the majority of all Shapley-Ames bright galaxies, plus cluster members in the Virgo Cluster core that might be usefully resolved by the Hubble Space Telescope (HST).
Abstract: A critical first step in determining distances to galaxies is to measure some property of primary objects such as stars of specific types, H II regions, and supernovae remnants that are resolved out of the general galactic star content With the completion of the Mount Wilson/Palomar/Las Campanas survey of bright galaxies in 1985, excellent large-scale photographs of the complete Shapley-Ames sample were on hand Most of the galaxies useful for distance scale calibration are in this collection This atlas contains photographs of 322 galaxies including the majority of all Shapley-Ames bright galaxies, plus cluster members in the Virgo Cluster core that might be usefully resolved by the Hubble Space Telescope (HST) Because of crowding and high background-disk surface brightness, the choice of field position is crucial for programs involving resolution of particular galaxies into stars The purpose of this atlas is to facilitate this choice Enough information is given herein (coordinates of the galaxy centers and the scale of the photography) to allow optimum placement of the HST wide-field planetary camera format of approximately 150 arc-seconds on a side
41 citations
TL;DR: The results of direct CCD imaging and long-slit medium-dispersion spectroscopy of the extended narrow-line-emitting gas in the nearby Seyfert 2 galaxy NGC 4388 are presented in this article.
Abstract: The results of direct CCD imaging and long-slit medium-dispersion spectroscopy of the extended narrow-line-emitting gas in the nearby Seyfert 2 galaxy NGC 4388 are presented. The spectra are used to investigate the distribution, kinematics, and ionization structure of the excited gas in the regions surrounding the nucleus out to a distance of about 4.8 kpc. The data support earlier suggestions that the galaxy, which appears to lie near the core of the Virgo cluster, has been tidally distorted, possibly by the nearby cluster core galaxies M84 or IC 3303. Much of the highly ionized gas in the galaxy appears to be distributed in two wide cones originating from the nucleus and extending above and below the disk. Explanations are offered for the distribution of this gas and for the remainder of the gas above and below the disk.
41 citations
TL;DR: The Magellanic irregular galaxy NGC 4214 and its interstellar medium were studied in this paper. But the authors only used near-and far-IR data and mm-wave CO observations to study the star-forming properties of NGC4214.
Abstract: Near- and far-IR data and mm-wave CO observations are used to study the star-forming properties of the Magellanic irregular galaxy NGC 4214 and its interstellar medium. The galaxy is forming stars at present at about 0.5-1 solar mass/yr in its central few arcmin, if the new stars follow the Salpeter initial mass function from 0.1 to 100 solar masses. This has been maintained for around a Hubble time, although some regions of the galaxy may undergo periods of enhanced and depressed star formation. Based on the mass of dust in emission at 160 microns, a plausible star formation efficiency of about 1.5 percent is estimated, if the H I gas does not take part in forming stars. Molecular masses derived using the H + 1 - 0 line and a conversion to M(H2) appropriate to spiral galaxies produces a mass estimate that is too low by a factor of five to ten.
25 citations
TL;DR: In this article, the molecular and ionized gas content of the spiral galaxy NGC 2146 has been investigated and the dynamical center of the galaxy lies toward a dense dust lane.
Abstract: New observations probing the molecular and ionized gas content of the ultrahigh surface brightness, peculiar spiral galaxy NGC 2146 are presented. The dynamical center of the galaxy lies toward a dense dust lane. The molecular mass of the galaxy in the central 15 kpc is 10 to the 10th solar. Strong emission from the central 5 kpc, as well as a string of H II regions extending along an arc 8 arcmin long are observed. Evidence is found for a high mass concentration within the central 100 pc, highly noncircular motions along the major axis, and a significant discrepancy between the velocities of the H II regions in the arc and those in the disk. The high-mass star formation efficiency is elevated by more than two orders of magnitude in the center of the galaxy relative to that in the outer disk. 25 references.
20 citations
TL;DR: The ESO400-G43 ( = 2034-356) is one of the brightest and largest blue compact galaxies known as discussed by the authors, and its morphology and spectral properties are consistent with a predominantly young stellar population and an extremely low mass to light ratio (M/LB = 0.1).
Abstract: Blue compact galaxies (BCGs) are characterized by their compact appearance and very blue colours1,2 indicative of a high star-formation rate. The metal abundances are low, suggesting that the present rate of star formation cannot have lasted for very long3 (unless the gas is being replenished). These galaxies are thus either truly young or their star formation takes place in short bursts3,4. ESO400-G43 ( = 2034–356) is one of the brightest and largest BCGs known. Observations in the 21-cm line with the Very Large Array (VLA) of the National Radio Astronomy Observatory reveal a massive (5×109 M⊙) slowly rotating H I halo. Optical observations obtained at the European Southern Observatory (ESO) show that the morphology and spectral properties are consistent with a predominantly young stellar population and an extremely low mass to light ratio (M/LB = 0.1). The luminous stars seem to be concentrated in a rapidly spinning central disk. Dark matter is dominating the mass at large radii.
18 citations
TL;DR: The repeated scattering of Ly-alpha radiation across a shock front results in a systematic blueshift which may greatly exceed the shock velocity vs and is proportional to cube root of (Nvs), where N is the column density of hydrogen atoms on either side of the shock front as discussed by the authors.
Abstract: The repeated scattering of Ly-alpha radiation across a shock front results in a systematic blueshift which may greatly exceed the shock velocity vs and is proportional to cube root of (Nvs), where N is the column density of hydrogen atoms on either side of the shock front. The blueshifting process is similar to the Fermi acceleration of cosmic rays and may be responsible for the blue asymmetric line profiles that have been observed in high-redshift Ly-alpha galaxies. The Ly-alpha line profile in 3C 326.1 is accounted for by a model in which shocks, driven into a population of interstellar clouds by a radio lobe, trigger the formation of ionizing stars and Fermi accelerate the Ly-alpha radiation emitted by H II regions surrounding those stars. Galaxy mergers, particularly between galaxies with low dust content, should produce Ly-alpha lines with strong blue wings.
TL;DR: The field galaxy contamination of galaxy quintets in Hickson's catalog of compact groups is estimated by computing the probability of the random projection of field galaxies on or near quartets in the catalog as mentioned in this paper.
Abstract: The field galaxy contamination of galaxy quintets in Hickson's catalog of compact groups is estimated by computing the probability of the random projection of field galaxies on or near quartets in the catalog. This is done by Monte Carlo simulations based on galaxy counts in fields surrounding the quartets. Thirty-five percent of all quintets are predicted to contain a single discordant redshift due to a projected field galaxy. This agrees with the observed number of four discordant quintets in 10. These results are consistent with the cosmological interpretation of galaxy redshifts.
TL;DR: In this article, a deep, high-resolution imaging of several sources from the high-redshift 3CR galaxy sample is presented, and very complex and unexpected morphologies are found.
Abstract: Deep, high spatial resolution imaging of several sources from the high-redshift 3CR galaxy sample is presented. Very complex and unexpected morphologies are found. All the galaxies observed so far are resolved, and most of them show multimodal sources. Significant color differences for the components of each galaxy are measured. An interpretation in terms of gravitational amplification/lensing by foreground galaxies or galactic clusters is proposed for 3C 238, 3C 241, and 3C 305.1, 3C 238 being the strongest candidate. The complexity of the 3CR galaxies like 3C 356, which includes a compact object, and 3C 326.1 shows that they are not normal ellipticals and their use as standard candles to test for galaxy evolution is therefore questionable. 29 references.
TL;DR: In this article, simple models for the motion of a rocket through a galaxy are examined, and it is found that the density distribution of the galaxy is important, and determines whether a given source can escape.
Abstract: It has been noted that the central source of an asymmetric nuclear galactic radio jet may experience considerable net thrust and consequently behave like a massive rocket. In this paper, simple models for the motion of a rocket through a galaxy are examined. It is found that the density distribution of the galaxy is important, and determines whether a given source can escape. Thus, observations of the location and velocity of a source relative to its galactic center may provide new constraints on models of the density distribution in galaxies. 35 references.
TL;DR: In this article, a complete high spatial resolution imaging survey of the highest red-shift 3CR radio galaxies is presented. But the use of the high-redshift radio-galaxies as standard candles for cosmological purposes without further precautions is questioned.
Abstract: This report continues a series of papers discussing a complete high spatial resolution imaging survey of the highest redshift 3CR radio galaxies. CCD observations of seven 3CR galaxies with redshifts between 1.176 and 1.841 are presented. Excellent seeing conditions facilitated resolution of most of the galaxies into multiple components. Two of the galaxies are located less than 4 arcsec from a foreground bright galaxy; it is suggested that they may be gravitationally amplified by more than one magnitude. One of the objects, 3C 194 at z = 1.779, is proposed as a gravitational lens candidate. For the other galaxies observed, different interpretations are considered. The use of the high-redshift 3CR radio-galaxies as standard candles for cosmological purposes without further precautions is questioned. 30 references.
TL;DR: In this article, the neutrino-dominated cosmological scenario is considered, and it is found that the clustering of galaxies could be suppressed relative to neutrinos to an extent that eliminates the timing problem.
Abstract: The timing problem of the neutrino-dominated cosmological scenario, i.e., the inferred young age for the large-scale structure versus the observationally indicated older age of galaxies and quasars, is considered. It can be resolved by antibiasing of galaxy formation. By applying a variety of alternative prescriptions for galaxy formation to N-body simulations of the neutrino scenario, it is found that the clustering of galaxies could be suppressed relative to the neutrinos to an extent that eliminates the timing problem. It requires that galaxies form preferentially in the flat sheets relative to the denser filaments and compact clusters. This could emerge either from differences in the efficiency of galaxy formation itself or from feedback influence from a first generation of objects (e.g., quasars) which suppresses the formation of incipient galaxies locally. Various illustrative examples are presented in order to quantify the requirements from such antibiasing mechanisms, and their physical plausibility is discussed. Other aspects of the neutrino cosmology are discussed in view of the proposed antibiasing, concluding that no fatal flaw is seen in this picture. 66 references.
01 Jan 1988
TL;DR: In this article, it was shown that technological civilizations of our type can originate in the Galaxy in a "belt of life", a narrow circular zone with the galactic orbit of the Sun inside.
Abstract: The hypothesis is substantiated, according to which technological civilizations of our type can originate in the Galaxy in a ‘belt of life’, a narrow circular zone with the galactic orbit of the Sun inside. This zone is characterized by specific conditions due to the corotation circle, an exceptional region of the Galaxy, passing through it. In the belt of life birth and death of civilizations should apparently occur in spiral arms because of supernova explosions. In this case, the lifetime of a civilization is the time of its motion along Galactic orbit between the adjacent spiral arms. In 3.3 109 years our civilization will enter the Perseus arm. It can be expected that in the Galaxy the ratio of the probable number of civilizations at a higher than ours — technological level to that at a lower technological level is of the order of 0, 7.
Journal Article•
TL;DR: In this paper, high-spatial-resolution imaging is presented for two radio galaxies from the 3C catalog, 3C 13 and 3C 256 with redshifts of 1.351 and 1.819, respectively.
Abstract: High-spatial-resolution imaging is presented for two radio galaxies from the 3C catalog, 3C 13 and 3C 256 with redshifts of 1.351 and 1.819, respectively. The excellent image quality obtained at CFHT, 0.6-arcsec FWHM for 3C 13 and 0.7-arcsec FWHM for 3C 256 in the R band, over long integration times, made it possible to resolve these distant galaxies into complex structures. As suggested by Le Fevre et al. (1987) for another source (the gravitational lens candidate 3C 324) an interpretation in terms of gravitational amplification by foreground galaxies or clusters of galaxies is proposed. 3C 13 appears to be the most serious candidate, since a foreground galaxy, with an absolute luminosity M(R) = 23.3 and a redshift z = 0.477, is only 3.9 in from the extended radio galaxy. 18 references.
TL;DR: In this paper, the origin and distribution of cosmic rays in the Galaxy is discussed by summarizing the literature on the radio and γ-ray studies of the Galaxy, discussing the propagation of cosmic ray in the interstellar medium, and listing the observed properties of the cosmic rays.
Abstract: The problem of the origin and distribution of cosmic rays in the Galaxy is introduced by summarizing the literature on the radio and γ-ray studies of the Galaxy, discussing the propagation of cosmic rays in the interstellar medium, and listing the observed properties of cosmic rays. The localization of cosmic-ray electrons to their parent galaxies is an indicator that processes leading to cosmic-ray production may be common to galaxies like our own. The studies of external galaxies are therefore relevant to our own and have the advantage of better perspective.
TL;DR: In this paper, optical imaging in both continuum and line wavelengths, spatially resolved optical spectroscopy, and 21 cm radio imaging of Markarian 266 are presented, which indicate that it is a recent merger.
Abstract: Optical imaging in continuum and line wavelengths, spatially resolved optical spectroscopy, and 21 cm radio imaging of Markarian 266 are presented. The galaxy has faint extended plumes of luminosity, which indicate that it is a recent merger. There are extended regions of blue luminosity suggestive of recent star formation, and remarkable structure in forbidden O III line emission. Spectroscopic data show the velocities and densities in the ionized gas. Radio observations taken with the VLA show that both nuclei are resolved radio sources, and that there is a third radio source between them which has no optical counterpart; 21-cm absorption is seen against the brighter optical nucleus, indicating possible infall. These results are discussed in terms of galaxy mergers, nuclear activation, and ionized gas. Mkn 266 has many similarities to Arp 220 and appears to be a somewhat lower-luminosity version of the IRAS ultraluminous galaxies.
01 Jan 1988
TL;DR: In this article, a deep CCD survey of field galaxies to U ≳ 25.5 verifies the steep slope in the ultraviolet galaxy counts found by Koo (1986) for 20 ≲ U ≲ 22.
Abstract: A deep CCD survey of field galaxies to U ≳ 25.5 verifies to fainter magnitudes the steep slope in the ultraviolet galaxy counts found by Koo (1986) for 20 ≲ U ≲ 22. The sensitivity to the epoch of galaxy formation of still fainter surveys at short wavelengths is discussed.
TL;DR: The N-body model of galaxy formation developed by Carlberg as mentioned in this paper, which contains both collisionless dark matter and an isothermal gas, is extended to include a simple description of gas cooling and star formation.
Abstract: The N-body model of galaxy formation developed by Carlberg (1988), which contains both collisionless dark matter and an isothermal gas, is extended to include a simple description of gas cooling and star formation. Two experiments were carried out to study the formation of galaxies and their clustering, one mimicking the formation of a small cluster in a background having Omega(i) = 5/3, and the other with Omega = 1, both with perturbations drawn from a density perturbation spectrum with n = -1. The resulting galaxies had many points of similarity to the galaxies in the universe, suggesting that this model is useful for investigations of the relation between cosmological quantities and galaxy properties. 42 references.
TL;DR: In this article, a review examines the present status of searches for star clusters in nearby galaxies and comments on problems of completeness in each case, and an attempt is made to redefine the terminology used to classify star clusters, and a simple but fairly universally applicable scheme is adopted.
Abstract: This review examines the present status of searches for star clusters in nearby galaxies and comments on problems of completeness in each case. To facilitate the discussion, an attempt is made to redefine the terminology used to classify star clusters, and a simple but fairly universally applicable scheme is adopted. Nonuniformities are found in the formation rates of clusters as a function of time and from galaxy to galaxy. The median ages of clusters in different galaxies are different and may be related to the mass and perhaps structure of the galaxy.
01 Jan 1988
TL;DR: In this article, the authors studied the evolution of galaxies at intermediate redshift (0.1 < z < 0.6) and showed that the appearance of an individual galaxy at high redshift is determined by local processes and thus the concept of generalised evolutionary correction can no longer be meaningful.
Abstract: Detailed studies of intermediate redshift (0.1 < z < 0.6) galaxies are changing our ideas of galaxy evolution. In rich clusters, extended star formation histories are found in some but not all early-type objects. Together with variable blue fractions, the activity observed suggests local processes dictate the appearance of an individual galaxy at high redshift and thus the concept of a generalised evolutionary correction can no longer be meaningful. In field samples, spectroscopic surveys indicate that if luminosity evolution is responsible for the steep galaxy number count relation, it must be of a luminosity-dependent form. Brief spectacular enhancements in star formation activity in otherwise low luminosity galaxies may explain the excess faint galaxies at B ~ 22. The similarity between the cluster and field activities is striking. The absence of high luminosity primeval galaxies may now be understood via the extended star formation observed in both samples, but a physical mechanism for the bursts of star formation seen remains to be found.
TL;DR: In this paper, high-quality images of M87 showed that the apparent major axis of the galaxy is perpendicular to the direction of the jet, which may explain the failure of previous studies to detect strong correlations between radio and optical position axes.
Abstract: High-quality images of M87 show that in the region 3-8 arcsec, the core region of integrated luminosity profiles, the apparent major axis of the galaxy is perpendicular to the direction of the jet. It is proposed that the galaxy has an oblate spheroidal core whose plane is perpendicular to the plasma jet. The measurements are close to the limit of what is currently feasible with ground-based observation - it is not possible to resolve core structure in more distant radio galaxies. This may explain the failure of previous studies to detect strong correlations between radio and optical position axes. 18 references.
01 May 1988
TL;DR: In this article, the characteristics of the background field of a two-body system are computed, under the assumption that the two bodies are in steady-state circular orbits, and the resulting field pattern is shown to correlate well with observed barred spiral galaxy structure.
Abstract: It has become accepted that the core of some galaxies could contain a huge mass such as a black hole, and there is now gathering evidence that some galaxy cores might contain a two-body system of such masses. Such a two-body system would create a global background gravitational field pattern throughout the galaxy. The characteristics of this background field are here computed, under the assumption that the two bodies are in steady-state circular orbits. The resulting field pattern is shown to correlate well with observed barred spiral galaxy structure.
01 Jan 1988
TL;DR: The work done on the determination of the merger time of binary galaxies and the decay time of satellite galaxies is reviewed in this paper, where estimates made for the merger times of some observed pairs are given.
Abstract: The process of energy transfer in galaxy interactions is discussed with particular reference to mergers. The work done on the determination of the merger time of binary galaxies and the decay time of satellite galaxies is reviewed. Estimates made for the merger time of some observed pairs are given.