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1.
Radial colour gradients in the globular clusters NGC 2808, NGC 1851, NGC 5139, NGC 5139, NGC 6388, NGC 6441, NGC 6541, NGC 6723, and NGC 7099 were searched byB-V and DDO photoelectric photometry, using a set of circular diaphragms. Two of the observed globular clusters, NGC 5139 (Cen) and NGC 7099 (M30), showedB-V and C(45–48) colour gradients; the colour C(42–45) is essentially constant in these clusters, which means that the physical reason for those gradients cannot be attributed to chemical composition variations, since C(42–45) is a good metal abundance indicator.B-V colours in the external regions of NGC 5139 and NGC 7099 were obtained by synthesizing the observed HR diagrams of these clusters. The ages and the relaxation times for NGC 5139 and NGC 7099 indicate that mass segregation must have taken place in both clusters, which is probably related to the observed colour gradients.  相似文献   

2.
This is a study of the population of B and Be stars in the young, relatively poor, diffuse stellar clusters NGC 6871 and NGC 6913. High resolution spectra are used to study the Hα line of eleven stars in order to detect emission. Emission profiles were found for three stars in the cluster NGC 6871; one of these is a known WR-star and the Be-star BD +35°3956 demonstrates the transition from the B to the Be phase. Spectra of seven of the B stars revealed no traces of emission in the Hα line. During the time of our observations, the Be star V1322 Cyg in the cluster NGC 6913 had a strong emission Hα line profile with substantial variability in intensity and equivalent width. Moderate resolution spectra of seven stars in the cluster NGC 6871 over wavelengths of 4420-4960 ? and ten stars in the cluster NGC 6913 over wavelengths of 4050-5100 ? are used to classify the series of B and Be stars spectrally and to estimate their T eff and log g. It was found that three of the stars are not members of the clusters NGC 6871 or NGC 6913. Translated from Astrofizika, Vol. 52, No. 2, pp. 257–274 (May 2009).  相似文献   

3.
PhotoelectricUBV magnitudes and colours have been determined for stars in the field of NGC 1931. The reddening across the cluster varies from 0 . m 33 to 1 . m 20. A distance of 2.16 kiloparsecs has been estimated for the cluster. It is concluded that the age of the cluster lies between the ages of NGC 6231 and NGC 2362 groups.  相似文献   

4.
Based on deep Hubble Space Telescope ACS/WFC images, we have performed stellar photometry for the spiral and lenticular galaxies NGC 4921 and NGC 4923 in the Coma cluster. The derived Hertzsprung-Russell diagrams show that, apart from the stellar population, NGC 4921 has several thousand globular clusters. The asymmetry of their apparent distribution proves that NGC 4921 is in close spatial proximity to NGC 4923. We have determined the positions of the peaks for the luminosity functions of globular clusters in the two galaxies, which has allowed us to measure the distance to this pair (D = 97±5 Mpc). In many cases, compact star-forming regions at the periphery of NGC 4921 are located at the ends of extended (up to 1.5 kpc) radial gas and dust filaments. The metallicity of young stars in these star-forming regions is close to that of the Sun (Z = 0.02).  相似文献   

5.
Results fromCMT 1T2 1T2 broad-band and DDO intermediate-band photometry are presented for G and K giants in the old open clusters NGC. 2482, NGC 3680, and IC 4651. Two independent photometric criteria have been used to separate red field stars from the physical members of the clusters. Recent calibrations of the DDO andCMT 1T2 systems have been used to derive reddening, distance moduli, metallicities, effective temperatures, and surface gravities. Rough estimates of masses have also been made. The giants of NGC 2482 and IC 4651 have CN strengths nearly identical to the Hyades giants, while those of NGC 3680 are slightly richer in CN than the nearby K giants.CMT1T2 abundance analysis in NGC 2482 and NGC 3680 yield [Fe/H]MT = - 0.1 ± 0.1 as derived from the iron lines, while abundances derived from the CNO - contaminated (C - M) index are 0.4 dex higher. BothCMT 1T2 and DDO data support the conclusion that 1C 4651, with [Fe/H] = + 0.2 ± 0.1, is on the metalrich side of the distribution of intermediate and old open clusters. Finally, the mass results suggest that the clump stars in NGC 3680 and. IC 4651 could have undergone mass loss before reaching their helium core burning phase of evolution. Supported in part by the Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) of Argentina. Visiting astronomer of Cerro Tololo Inter-American Observatory supported by the National Science Foundation under contract No. AST 74-04128.  相似文献   

6.
The hydrogen Balmer‐α emission line spectrum of ten diffuse ionization sources in the Milk Way – NGC 40 (WC8), NGC 2022, NGC 6210, NGC 6618 (M17, Sh2‐45), NGC 6720 (M57), NGC 6781, NGC 6888 (Sh2‐105), NGC 6992 (Sh2‐103), NGC 7635 (Sh2‐162,) and IC 1848 (Sh2‐199) – has been investigated using a dual etalon Fabry‐Pérot optical spectrometer (DEFPOS) aatached to the 150 cm RTT150 telescope at TUBITAK National Observatory (TUG, Antalya, Turkey: 36° 51′ N; 30° 20′ E; elevation: 2547 m). All of our galactic Hα observations discussed in this paper were carried out during the nights of 2013 June 21–24 with exposure time of 3600 s. As main results the intensity, the full width at half maximum, and the radial velocity with respect to the LSR have been determined for each data set. The intensities, the radial velocities, and the line widths of the Hα emission line vary from 59.15 to 8923.44 R, –46.72 to +54.07 km s–1, and 31.4 to 48.01 km s–1, respectively. The radial velocities and the half‐widths of the Hii regions and planetary nebulae determined from our measurements are found tobe consistent with values given in literature, especially with those in Schneider et al. (1983) and Fich et al. (1990). (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

7.
We have conducted UBVRI and Hα CCD photometry of five barred galaxies (NGC 2523, NGC 2950, NGC 3412, NGC 3945 and NGC 5383),along with SPH simulations, in order to understand the origin of young stellar populations in the nuclei of barred galaxies. The Hα emission, which is thought to be emitted by young stellar populations, is either absent or strongly concentrated in the nuclei of early-type galaxies (NGC 2950, NGC 3412 and NGC 3945),while they are observed in the nuclei and circumnuclear regions of intermediate-type galaxies with strong bars (NGC 2523 and NGC 5383).SPH simulations of realistic mass models for these galaxies show that some disc material can be driven into the nuclear region by a strong bar potential. This implies that the young stellar populations in the circumnuclear regions of barred galaxies can be formed out of such gas. The existence of nuclear dust lanes is an indication of an ongoing gas inflow and extremely young stellar populations in these galaxies, because nuclear dust lanes such as those in NGC 5383 are not long-lasting features according to our simulations. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

8.
On the basis of photographs from the 6 m Large Azimuthal Telescope and the Hubble Space Telescope, VRI photometry of stars in 11 galaxies in the NGC 1023 group has been carried out. The distances to these galaxies were determined by the method of brightest stars. The distances to NGC 925 and NGC 1023 were determined from the position of the top of the red giant branch (the TRGB method). From the calculated average and root-mean-square distances to the NGC 1023 group (10.3 ± 2.2 Mpc and 9.7 ± 0.5 Mpc) the Hubble constant in this direction was determined: H 0R = 75 ± 8 km·sec-1·Mpc-1 and H 0M = 81 ± 5 km ·sec-1·Mpc-1.  相似文献   

9.
The photometry and kinematics of the interacting galaxy system Arp 118 are presented. Its eastern component, NGC 1144, has a Seyfert 2 nucleus and is dominated by a ring-like structure of giantHii regions, the radial velocities of which vary by more than 1000 km s–1. Kinematical models including a close encounter with the elliptical companion NGC 1143 lead to extremely high values for the rotational velocity, the mass of NGC 1144 and itsM/L ratio.  相似文献   

10.
We present UBVRCIC magnitudes of 49 comparison stars in the fields of the Seyfert galaxies Mrk 335, Mrk 79, Mrk 279, Mrk 506, 3C 382, 3C 390.3, NGC 6814, Mrk 304, Ark 564, and NGC 7469 in order to facilitate the photometric monitoring of these objects; 36 of the stars have not been calibrated before. The comparison stars are situated in 5 × 5 arcmin fields centred on the Seyfert galaxies, their V band flux ranges from 11.7 to 18.2 mag with a median value of 16.3 mag, and their B – V colour index ranges from 0.4 to 1.6 mag with a median value of 0.8 mag. The median errors of the calibrated UBVRCIC magnitudes are 0.08, 0.04, 0.03, 0.04, and 0.06 mag, respectively. Comparison stars were calibrated for the first time in three of the fields (Mrk 506, 3C 382, and Mrk 304). The comparison sequences in the other fields were improved in various aspects. Extra stars were calibrated in four fields (Mrk 335, Mrk 79, NGC 6814, and NGC 7469) – most of these stars are fainter and are situated closer to the Seyfert galaxies compared to the existing comparison stars. The passband coverage of the sequences in five fields (Mrk 335, Mrk 79, Mrk 279, NGC 6814, and Ark 564) was complemented with the U band. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

11.
We present a brief account of the theory on which the novel method of ‘Fourier‐resolved spectroscopy’ is based. We summarize the results from the past application of this method to the study of Galactic Black Hole candidate sources and MCG‐6‐30‐15, and we present new results from the Fourier‐resolved spectroscopy of archival XMM‐Newton data of five AGN, namely, Mrk 766, NGC 3516, NGC 3783, NGC 4051 and Ark 564. When we combine all the past and present results from Galactic sources and AGN, we find that the slope of the Fourier‐resolved spectra in accreting black hole systems decreases with increasing frequency as ∝ f –0.25, irrespective of whether the system is in its High or Low state. We find significant evidence that the iron line in Mrk 766, NGC 3783 and NGC 4051 is variable on time scales ∼1 day – 1 hour. There is an indication that, just like in Galactic sources, the equivalent width of the line in the Fourier‐resolved spectra of AGN decreases with increasing frequency. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

12.
We present spectrophotometry andUBV photometry of the central region of spiral galaxies. The sample consists of the Seyfert galaxies NGC 1566, 3783 and IC 4329A; NGC 1097, 2997, and 5236 containing peculiar nucleus and NGC 5530, 5643, and 6699 with normal nucleus.The stellar composition of the nuclei was derived by treating the equivalent widths of a sample of absorption lines with the method of constrained nonlinear optimization. The observed continua and theUBV colours were compared with the theoretical results in order to obtain the internal reddening and the contribution of the hot gas or non-thermal radiation. The age of the last cycle of star formation, the internal absorption and the theoretical relations M/L and H/K Caii present differences among the three types of nuclei.  相似文献   

13.
Initial results on the iron K‐shell line and reflection component in several AGN observed as part of the Suzaku Guaranteed Time program are reviewed. This paper discusses a small sample of Compton‐thin Seyferts observed to date with Suzaku; namely MCG‐5‐23‐16, MCG‐6‐30‐15, NGC4051, NGC3516, NGC2110, 3C 120 and NGC2992. The broad iron Kα emission line appears to be present in all but one of these Seyfert galaxies, while the narrow core of the line from distant matter is ubiquitous in all the observations. The iron line in MCG‐6‐30‐15 shows the most extreme relativistic blurring of all the objects, the red‐wing of the line requires the inner accretion disk to extend inwards to within 2.2R g of the black hole, in agreement with the XMM‐Newton observations. Strong excess emission in the Hard X‐ray Detector (HXD) above 10 keV is observed in many of these Seyfert galaxies, consistent with the presence of a reflection component from reprocessing in Compton‐thick matter (e.g. the accretion disk). Only one Seyfert galaxy (NGC 2110) shows neither a broad iron line nor a reflection component. The spectral variability of MCG‐6‐30‐15, MCG‐5‐23‐16 and NGC 4051 is also discussed. In all 3 cases, the spectra appear harder when the source is fainter, while there is little variability of the iron line or reflection component with source flux. This agrees with a simple two component spectral model, whereby the variable emission is the primary power‐law, while the iron line and reflection component remain relatively constant. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

14.
A new technique is used to derive the extinction and age of populations in the interacting galaxies NGC 5194 & NGC 5195 from high-S/Nmulti-colour photometric data. A new evolutionary scenario of the interaction is proposed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

15.
The detection of trailing arms in twenty spiral galaxies, completed by the 60s, allowed one to suggest the overwhelming prevalence of this sense of rotation. Pasha and Dambis (1982) have recently determined the direction of rotation in a further 54 galaxies and found two leading spirals, NGC 4490 and NGC 5395. The current sample of galaxies with an established sense of rotation contains 79 trailing and two leading systems. The two spirals found to be leading belong to M51 type galaxies.In this paper we present a more detailed investigation of the system NGC 4490/85 which confirms that the arms in NGC 4490 are leading. Statistics are invoked to estimate a probable percentageX p and an upper limitX up of galaxies with leading arms. It gives, for 79 trailing and two leading spirals, the valuesX p 3.5% andX up 8.2%.  相似文献   

16.
We have performed photometric B, V, and R observations of nine disk galaxies that presumably have abnormally low total mass-to-light (M/L) ratios for given color indices. Our data on surface photometry are used to analyze the possible causes of anomalous M/L estimates. In many cases, these can be the result of errors in photometry or rotational velocity determination but can also reflect the real peculiarities of the stellar composition of galaxies. Comparison of the photometric and dynamical disk mass estimates obtained by analyzing the rotational velocities shows that low M/L values for a given color index are probably real for some of the galaxies. This is primarily true of NGC 4826 (Sab), NGC 5347 (Sab), and NGC 6814 (Sb). The small number of such galaxies suggests that the stellar initial mass function is universal. However, a small fraction of galaxies probably may have a non-typical mass function “depleted” in low-mass stars. Such galaxies require a more careful study.  相似文献   

17.
Based on archival Hubble Space Telescope ACS/WFC images, we have performed stellar photometry for more than 0.6 million stars in the interacting galaxies NGC 5194 and NGC 5195 of the M51 system. Stars of various ages have been identified on the constructed Hertzsprung-Russell diagram: blue and red supergiants, AGB stars, and red giants. The distance to M51 has been measured from the position of the tip of the red giant branch, D = 9.9 ± 0.7 Mpc. We have determined the change in the metallicity of red supergiants along the galactic radius in NGC 5194. Despite the gravitational interaction, the distribution of stars in NGC 5194 does not differ from that in isolated galaxies. The asymmetric stellar structures of NGC5195 (the so-called “feathers”) formed through the interaction of two galaxies have been found to consist mostly of AGB stars.  相似文献   

18.
Detailed abundances are measured in cool (K type) supergiants in LMC young populous clusters (NGC 2004, NGC 2100 and NGC 1818), and compared to those, recently observed in samples of field supergiants in both Magellanic Clouds. This completes the work already done onthe SMC cluster NGC 330 (Hill et al., 1997b).The analysis of the field supergiants showed no evidence of any abundance dispersion among the stars, compatible with a well mixed gas in thesegalaxies. However, previous determinations of the metallicity ofNGC 330 and NGC 1818 gave values well below the respective field values. This difference is seeked, using a homogeneous method for the field andcluster samples, and the abundance ratios of various elements are examined. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

19.
Two very young star clusters, NGC 654 and IC 5146 are studied using photographic polarization measures with limiting magnitudeB=15m,with a view to determining the nature of magnetic fields in the vicinities of these clusters.Starlight from NGC 654 is found to be polarized in a direction parallel to the galactic plane, the fainter members being more strongly polarized than the brighter ones.Polarization of starlight in IC 5146 is found to be very variable in both magnitude and direction, indicating the presence of complex magnetic fields within the cluster.  相似文献   

20.
In this paper we analyse the relations between a previously described oblate Jaffe model for an ellipsoidal galaxy and the observed quantities for NGC 2974, and obtain the length and velocity scales for a relevant elliptical galaxy model. We then derive the finite total mass of the model from these scales, and finally find a good fit of an isotropic oblate Jaffe model by using the Gauss-Hermite fit parameters and the observed ellipticity of the galaxy NGC 2974. The model is also used to predict the total luminous mass of NGC 2974, assuming that the influence of dark matter in this galaxy on the image, ellipticity and Gauss-Hermite fit parameters of this galaxy is negligible within the central region, of radius 0.5R e.  相似文献   

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