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1.
A. A. Yeghiazaryan T. A. Nazaryan A. A. Hakobyan 《Journal of Astrophysics and Astronomy》2016,37(1):1
The quartet of galaxies NGC 7769, 7770, 7771 and 7771A is a system of interacting galaxies. Close interaction between galaxies caused characteristic morphological features: tidal arms and bars, as well as an induced star formation. In this study, we performed the Fabry–Perot scanning interferometry of the system in H a line and studied the velocity fields of the galaxies. We found that the rotation curve of NGC 7769 is weakly distorted. The rotation curve of NGC 7771 is strongly distorted with the tidal arms caused by direct flyby of NGC 7769 and flyby of a smaller neighbor NGC 7770. The rotation curve of NGC 7770 is significantly skewed because of the interaction with the much massive NGC 7771. The rotation curves and morphological disturbances suggest that the NGC 7769 and NGC 7771 have passed the first pericenter stage, however, probably the second encounter has not happened yet. Profiles of surface brightness of NGC 7769 have a characteristic break, and profiles of color indices have a minimum at a radius of intensive star formation induced by the interaction with NGC 7771. 相似文献
2.
A. A. Hakobyan A. R. Petrosian G. A. Mamon B. McLean D. Kunth M. Turatto E. Cappelaro F. Mannucci R. J. Allen N. Panagia M. Della Valle 《Astrophysics》2009,52(1):40-53
The determination of the supernova (SN) rate is based not only on the number of detected events, but also on the properties
of the parent galaxy population. This is the first paper of a series aimed at obtaining new, refined, SN rates from a set
of five SN surveys, by making use of a joint analysis of near-infrared (NIR) data. We describe the properties of the 3838
galaxies that were monitored for SNe events, including newly determined morphologies and their DENIS, and POSS-II/UKST I,
2MASS and DENIS J and Ks and 2MASS H magnitudes. We have compared 2MASS, DENIS and POSS-II/UKST IJK magnitudes in order to find possible systematic
photometric shifts in the measurements. The DENIS and POSS-II/UKST I band magnitudes show large discrepancies (mean absolute
difference of 0.4 mag.), mostly due to different spectral responses of the two instruments, with an important contribution
(0.33 mag rms) from the large uncertainties in the photometric calibration of the POSS-II and UKST photographic plates. In
the other wavebands, the limiting near infrared magnitude, morphology, and inclination of the galaxies are the most influential
factors which affect the determination of photometry of the galaxies. Nevertheless, no significant systematic differences
have been found between any pair of NIR magnitude measurements, except for a few percent of galaxies showing large discrepancies.
This allows us to combine DENIS and 2MASS data for the J and Ks filters.
Published in Astrofizika, Vol. 52, No. 1, pp. 47–62 (Februay 2009). 相似文献
3.
The galaxy NGC6384 has been observed with an IPCS through Hα and [NII] narrow-band interference filters for direct imagery with the 2.6-m Byurakan telescope. We studied the main physical
parameters of the identified 98 HII regions, their diameter and luminosity functions, as well the [NII]/Hα ratio distribution. The integrated distribution function of the HII region diameters can be well fitted by the exponential
function. The characteristic diameter has the value (Do = 217 pc) predicted for a galaxy of its measured luminosity. The luminosity
function of HII regions has a double power law profile with relatively shallow slope at low luminosities (α = −0.4), an abrupt
turnover at logL(Hα) ≈ 38.75, and sharper slope at higher luminosities (α = −2.3). The correlation between the luminosity and diameter of HII
regions confirms that in general they are constant density, radiation-bound systems. [NII]/Hα ratio data for the HII regions show that there is a negative radial gradient of [NII]/Hα. In the central region of the galaxy, nitrogen abundance is higher than in the periphery. The properties of the HII region
population of this AGN galaxy do not differ significantly from the properties of the HII region population of the “normal”
galaxies. Reexamining the location of the type Ia SN 1971L in the galaxy, we confirm that it lies on the spiral arm at about
8″.6 far from the closest HII region N 53 (F81). Such a location can be taken as proof that the progenitor of this SN does
not belong to an old, evolved stellar population.
Published in Astrofizika, Vol. 50, No. 4, pp. 519–533 (November 2007). 相似文献
4.
T. A. Nazaryan A. R. Petrosian A. A. Hakobyan V. Z. Adibekyan D. Kunth G. A. Mamon M. Turatto L. S. Aramyan 《Astrophysics and Space Science》2013,347(2):365-374
We investigate the influence of close neighbor galaxies on the properties of supernovae (SNe) and their host galaxies using 56 SNe located in pairs of galaxies with different levels of star formation (SF) and nuclear activity. The statistical study of SN hosts shows that there is no significant difference between morphologies of hosts in our sample and the larger general sample of SN hosts in the Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8). The mean distance of type II SNe from nuclei of hosts is greater by about a factor of 2 than that of type Ibc SNe. The distributions and mean distances of SNe are consistent with previous results compiled with the larger sample. For the first time it is shown that SNe Ibc are located in pairs with significantly smaller difference of radial velocities between components than pairs containing SNe Ia and II. We consider this as a result of higher star formation rate (SFR) of these closer systems of galaxies. SN types are not correlated with the luminosity ratio of host and neighbor galaxies in pairs. The orientation of SNe with respect to the preferred direction toward neighbor galaxy is found to be isotropic and independent of kinematical properties of the galaxy pair. 相似文献
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6.
A. A. Hakobyan 《Astrophysics》2008,51(1):69-76
This is a statistical study of the properties of type Ib/c and II supernovae and of the integral parameters of their spiral
host galaxies. The methods of one-dimensional and multivariate statistics were applied to the data sample. It was found that
the Ib/c supernovae are more concentrated radially toward the centers of the galaxies than those of type II. The distributions
of the radial distances RSN/R25 for the type Ib/c and II supernovae in active galaxies are more concentrated toward the center than in normal galaxies. This
effect is stronger for type Ib/c than for type II supernovae.
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Translated from Astrofizika, Vol. 51, No. 1, pp. 89–98 (February 2008). 相似文献
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8.
Shake‐table tests of a reinforced concrete frame designed following modern codes: seismic performance and damage evaluation 
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下载免费PDF全文 This paper presents shake‐table tests conducted on a two‐fifths‐scale reinforced concrete frame representing a conventional construction design under current building code provisions in the Mediterranean area. The structure was subjected to a sequence of dynamic tests including free vibrations and four seismic simulations in which a historical ground motion record was scaled to levels of increasing intensity until collapse. Each seismic simulation was associated with a different level of seismic hazard, representing very frequent, frequent, rare and very rare earthquakes. The structure remained basically undamaged and within the inter‐story drift limits of the ‘immediate occupancy’ performance level for the very frequent and frequent earthquakes. For the rare earthquake, the specimen sustained significant damage with chord rotations of up to 28% of its ultimate capacity and approached the upper bound limit of inter‐story drift associated with ‘life safety’. The specimen collapsed at the beginning of the ‘very rare’ seismic simulation. Besides summarizing the experimental program, this paper evaluates the damage quantitatively at the global and local levels in terms of chord rotation and other damage indexes, together with the energy dissipation demands for each level of seismic hazard. Further, the ratios of column‐to‐beam moment capacity recommended by Eurocode 8 and ACI‐318 to guarantee the formation of a strong column‐weak beam mechanism are examined. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
9.
Jafar Sadeghi Martiros Khurshudyan Margarit Hakobyan Hoda Farahani 《天文和天体物理学研究(英文版)》2015,(2):175-190
We consider a tachyonic scalar field as a model of dark energy with interaction between components in the case of variable G and Λ. We assume a flat Universe with a specific form of scale factor and study cosmological parameters numerically and graphically. Statefinder analysis is also performed. For a particular choice of interaction parameters we succeed in obtaining an analytical expression of densities. We find that our model will be stable at the late stage but there is an instability in the early Universe, so we propose this model as a realistic model of our Universe. 相似文献
10.
Seismic performance and damage evaluation of a reinforced concrete frame with hysteretic dampers through shake‐table tests 下载免费PDF全文
下载免费PDF全文 Passive energy dissipation devices are increasingly implemented in frame structures to improve their performance under seismic loading. Most guidelines for designing this type of system retain the requirements applicable to frames without dampers, and this hinders taking full advantage of the benefits of implementing dampers. Further, assessing the extent of damage suffered by the frame and by the dampers for different levels of seismic hazard is of paramount importance in the framework of performance‐based design. This paper presents an experimental investigation whose objectives are to provide empirical data on the response of reinforced concrete (RC) frames equipped with hysteretic dampers (dynamic response and damage) and to evaluate the need for the frame to form a strong column‐weak beam mechanism and dissipate large amounts of plastic strain energy. To this end, shake‐table tests were conducted on a 2/5‐scale RC frame with hysteretic dampers. The frame was designed only for gravitational loads. The dampers provided lateral strength and stiffness, respectively, three and 12 times greater than those of the frame. The test structure was subjected to a sequence of seismic simulations that represented different levels of seismic hazard. The RC frame showed a performance level of ‘immediate occupancy’, with maximum rotation demands below 20% of the ultimate capacity. The dampers dissipated most of the energy input by the earthquake. It is shown that combining hysteretic dampers with flexible reinforced concrete frames leads to structures with improved seismic performance and that requirements of conventional RC frames (without dampers) can be relieved. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献