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1.
We present long-slit observations in the optical and near-infrared of 14 H  ii regions in the spiral galaxies NGC 628, 925, 1232 and 1637, all of them reported to have solar or oversolar abundances according to empirical calibrations. For seven of the observed regions, ion-weighted temperatures from optical forbidden auroral to nebular line ratios are obtained and, for six of them, the oxygen abundances derived by standard methods turn out to be significantly lower than solar. The other one, named CDT1 in NGC 1232, shows an oxygen abundance of     , and constitutes, to the best of our knowledge, the first high-metallicity H  ii region for which accurate line temperatures, and hence elemental abundances, have been derived.
For the rest of the regions no line temperature measurements could be made, and the metallicity has been determined by means of both detailed photoionization modelling and the sulphur abundance parameter S 23. Only one of these regions shows values of O 23 and S 23 implying a solar or oversolar metallicity.
According to our analysis, only two of the observed regions can therefore be considered as of high metallicity. These two fit the trends previously found in other high-metallicity H  ii regions, i.e., N/O and S/O abundance ratios seem to be higher and lower than solar respectively.  相似文献   

2.
The relationship between the black hole mass and velocity dispersion indicated with [O  iii ] linewidth is investigated for a sample of 87 flat-spectrum radio quasars selected from the Sloan Digital Sky Survey Data Release 3 quasar catalogue. We found that the   M BH−σ[O III]  relation is different from the Tremaine et al. relation for nearby inactive galaxies, with a larger black hole mass at given velocity dispersion. There is no strong evidence of cosmology evolution in the   M BH−σ[O III]  relation up to   z ∼ 0.8  . A significant correlation between the [O  iii ] luminosity and broad-line region (BLR) luminosity is found. When transferring the [O  iii ] luminosity to narrow-line region (NLR) luminosity, the BLR luminosity is, on average, larger than the NLR one by about one order of magnitude. We found a strong correlation between the synchrotron peak luminosity and NLR luminosity, which implies a tight relation between the jet physics and accretion process.  相似文献   

3.
Stellar velocity dispersion in narrow-line Seyfert 1 galaxies   总被引：1，自引：0，他引：1  
Several authors have recently explored, for narrow-line Seyfert 1 galaxies (NLS1s), the relationship between black hole mass ( M BH) and stellar velocity dispersion (σ*). Their results are more or less in agreement and seem to indicate that NLS1s fill the region below the fit obtained by Tremaine et al., showing a range of σ* similar to that of Seyfert 1 galaxies, and a lower M BH. Until now, the [O  iii ] width has been used in place of the stellar velocity dispersion, but some indications have begun to arise against the effectiveness of the gaseous kinematics in representing the bulge potential, at least in NLS1s. Bian & Zhao have stressed the urgency of producing true σ* measurements. Here, we present new stellar velocity dispersions obtained through direct measurements of the Ca  ii absorption triplet (∼8550 Å) in the nuclei of eight NLS1 galaxies. The resulting σ* values and a comparison with σ[O III] confirm our suspicion that [O  iii ] typically overestimates the stellar velocity dispersion. We demonstrate that NLS1s follow the   M BH–σ*  relation as Seyfert 1, quasars and non-active galaxies.  相似文献   

4.
We present high signal-to-noise ratio spectrophotometric observations of seven luminous H  ii galaxies. The observations have been made with the use of a double-arm spectrograph which provides spectra with a wide wavelength coverage, from 3400 to 10 400 Å free of second-order effects, of exactly the same region as that of a given galaxy. These observations are analysed applying a methodology designed to obtain accurate elemental abundances of oxygen, sulphur, nitrogen, neon, argon and iron in the ionized gas. Four electron temperatures and one electron density are derived from the observed forbidden line ratios using the five-level atom approximation. For our best objects, errors of 1 per cent in t e([O  iii ]), 3 per cent in t e([O  ii ]) and 5 per cent in t e([S  iii ]) are achieved with a resulting accuracy of 7 per cent in total oxygen abundances, O/H.
The ionization structure of the nebulae can be mapped by the theoretical oxygen and sulphur ionic ratios, on the one side, and the corresponding observed emission line ratios, on the other – the η and η' plots. The combination of both is shown to provide a means to test photoionization model sequences presently applied to derive elemental abundances in H  ii galaxies.  相似文献   

5.
Using a sample of 14 BeppoSAX and 74 Swift GRBs with measured redshift we tested the correlation between the intrinsic peak energy of the time-integrated spectrum,   E p, i   , the isotropic-equivalent peak luminosity,   L p,iso  , and the duration of the most intense parts of the GRB computed as T 0.45 ('Firmani correlation'). For 41 out of 88 GRBs we could estimate all of the three required properties. Apart from 980425, which appears to be a definite outlier and notoriously peculiar in many respects, we used 40 GRBs to fit the correlation with the maximum likelihood method discussed by D'Agostini, suitable to account for the extrinsic scatter in addition to the intrinsic uncertainties affecting every single GRB. We confirm the correlation. However, unlike the results by Firmani et al., we found that the correlation does have a logarithmic scatter comparable with that of the   E p, i – E iso  ('Amati') correlation. We also find that the slope of the product   L p,iso  T 0.45  is equal to ∼0.5, which is consistent with the hypothesis that the   E p, i – L p,iso– T 0.45  correlation is equivalent to the   E p, i – E iso  correlation (slope ∼0.5). We conclude that, based on presently available data, there is no clear evidence that the   E p, i – L p,iso– T 0.45  correlation is different (both in terms of slope and dispersion) from the   E p, i – E iso  correlation.  相似文献   

6.
In a former paper, we have presented spectra of 64 active, nine normal and five starburst galaxies in the region around the near-infrared calcium triplet (CaT) absorption lines and the [S  iii ]λ9069 line. In the present paper, we analyse the CaT strength ( W CaT) and kinematical products derived in that study, namely stellar  (σ★)  and ionized gas (σgas) velocity dispersions. Our main results may be summarized as follows. (1) Type 2 Seyfert galaxies show no sign of dilution in W CaT with respect to the values spanned by normal galaxies, even when optical absorption lines such as the Ca  ii K band at 3933 Å are much weaker than in old, bulge-like stellar populations. (2) The location of type 2 Seyfert galaxies in the   W CaT– W CaK  plane is consistent with evolutionary synthesis models. The implication is that the source responsible for the dilution of optical lines in these active galactic nuclei (AGN) is a young stellar population, rather than an AGN featureless continuum, confirming the conclusion of the pioneer study of Terlevich, Díaz & Terlevich. (3) In type 1 Seyfert galaxies, both   W [S  iii ]  and W CaT tend to be diluted due to the presence of a non-stellar component, in agreement with the unification paradigm. (4) A comparison of  σ★  with σgas (obtained from the core of the [S  iii ] emitting line) confirms the existence of a correlation between the typical velocities of stars and clouds of the narrow line region. The strength and scatter around this correlation are similar to those previously obtained from the [O  iii ]λ5007 linewidth.  相似文献   

7.
Absolute integrated line fluxes of H  ii regions have been measured using a Fabry–Perot spectrophotometer. We describe the observations and calibration procedures. Fluxes are given for 36 H  ii regions with Galactocentric distances ranging from 6.6 to 17.7 kpc. Several emission lines have been measured, mainly [O  ii ] λλ 3726 and 3629, H β , [O  iii ] λ 5007, He  i λ 5876 and H α . The very faint [O  iii ] λ 4363 line has been measured in six regions, allowing a direct determination of the electron temperature. New photometric distances have been derived based on data from the literature. A discussion of these results in terms of extinction, electron density and temperature, and oxygen and helium abundances is given in Paper II.  相似文献   

8.
In general, H  ii regions do not show clear signs of self-enrichment in products from massive stars  ( M ≥ 8 M⊙)  . In order to explore why I modelled the contamination with Wolf–Rayet star ejecta of metal-poor  ( Z = 0.001)  H  ii regions, ionized either by a  106 M⊙  cluster of coeval stars (cluster 1) or by a cluster resulting from continuous star formation at a rate of  1 M⊙ yr−1  (cluster 2). The clusters have   Z = 0.001  and a Salpeter initial mass function from 0.1 to  120 M⊙  . Independent one-dimensional constant density simulations of the emission-line spectra of unenriched H  ii regions were computed at the discrete ages 1, 2, 3, 4 and 5 Myr, with the photoionization code cloudy , using as input, radiative and mechanical stellar feedbacks predicted by the evolutionary synthesis code starburst99 . Each H  ii region was placed at the outer radius of the adiabatically expanding superbubble of Mac Low & McCray. For models with thermal and ionization balance time-scales of less than 1 Myr, and with oxygen emission-line ratios in agreement with observations, the volume of the superbubble and the H  ii region was uniformly and instantaneously polluted with stellar ejecta predicted by starburst99 . I obtained a maximum oxygen abundance enhancement of 0.025 dex, with cluster 1, at 4 Myr. It would be unobservable.  相似文献   

9.
We examine the effects of cooling flows on the T X– L Bol relation for a sample of the most X-ray luminous ( L Bol > 1045 erg s−1) clusters of galaxies known. Using high-quality ASCA X-ray spectra and ROSAT images we explicitly account for the effects of cooling flows on the X-ray properties of the clusters and show that this reduces the previously noted dispersion in the T X– L Bol relationship. More importantly, the slope of the relationship is flattened from L Bol ∝  T 3X to approximately L Bol ∝  T 2X, in agreement with recent theoretical models which include the effects of shocks and pre-heating on the X-ray gas. We find no evidence for evolution in the T X– L Bol relation within z  ∼ 0.3. Our results demonstrate that the effects of cooling flows must be accounted for before cosmological parameters can be determined from X-ray observations of clusters. The results presented here should provide a reliable basis for modelling the T X– L Bol relation at high X-ray luminosities.  相似文献   

10.
Continuum-subtracted dereddened images in the light of several atomic lines show the presence of an extended bipolar nebula surrounding η Carinae with size ∼100×45 arcsec2 (1.3×0.5 pc2). This feature is best delineated in [O  iii ] 5007. The geometrical disposition and mass of the shell suggest that it was formed by mass ejections from η Carinae. The dynamic age of the nebula is ∼13 000/ V 7 yr, where V 7 is the mean expansion velocity in 100 km s−1, and its mass is between 5 and 10 M⊙. The nebula is photoionized and composed of unprocessed material. The major axes of the nebula and of the Homunculus are nearly perpendicular. We also report the discovery of elongated emission knots prominent in [N  ii ] located 64 to 100 arcsec away from η Carinae, which implies that they were ejected either centuries ago or at a more recent date but with extremely large velocities.  相似文献   

11.
The evolution of the abundance of galaxy clusters depends sensitively on the value of the cosmological density parameter, Ω0. Recent ASCA data are used to quantify this evolution as measured by the cluster X-ray temperature function. A χ2 minimization fit to the cumulative temperature function, as well as a maximum-likelihood estimate (which requires additional assumptions about cluster luminosities), leads to the estimate Ω0 ≈ 0.45 ± 0.25 (1σ statistical error). Various systematic uncertainties are considered, none of which significantly enhances the probability that Ω0 = 1. These conclusions hold for models with or without a cosmological constant, i.e., with Λ0 = 0 or Λ0 = 1 − Ω0. The statistical uncertainties are at least as large as any of the individual systematic errors that have been considered here, suggesting that additional temperature measurements of distant clusters will allow an improvement in this estimate. An alternative method that uses the highest redshift clusters to place an upper limit on Ω0 is also presented and tentatively applied, with the result that Ω0  1 can be ruled out at the 98 per cent confidence level. Whilst this method does not require a well-defined statistical sample of distant clusters, there are still modelling uncertainties that preclude a firmer conclusion at this time.  相似文献   

12.
We present the results of a search for strong H α emission line galaxies (rest frame equivalent widths greater than 50 Å) in the z ≈0.23 cluster Abell 2390. The survey contains 1189 galaxies over 270 arcmin2, and is 50 per cent complete at M r ≈−17.5+5 log  h . The fraction of galaxies in which H α is detected at the 2 σ level rises from 0.0 in the central regions (excluding the cD galaxy) to 12.5±8 per cent at R 200. For 165 of the galaxies in our catalogue, we compare the H α equivalent widths with their [O  ii ] λ 3727 equivalent widths, from the Canadian Network for Observational Cosmology (CNOC1) spectra. The fraction of strong H α emission line galaxies is consistent with the fraction of strong [O  ii ] emission galaxies in the CNOC1 sample: only 2±1 per cent have no detectable [O  ii ] emission and yet significant (>2 σ ) H α equivalent widths. Dust obscuration, non-thermal ionization, and aperture effects are all likely to contribute to this non-correspondence of emission lines. We identify six spectroscopically 'secure' k+a galaxies [ W 0(O  ii )<5 Å and W 0(H δ )≳5 Å]; at least two of these show strong signs in H α of star formation in regions that are covered by the slit from which the spectra were obtained. Thus, some fraction of galaxies classified as k+a based on spectra shortward of 6000 Å are likely to be undergoing significant star formation. These results are consistent with a 'strangulation' model for cluster galaxy evolution, in which star formation in cluster galaxies is gradually decreased, and is neither enhanced nor abruptly terminated by the cluster environment.  相似文献   

13.
We have studied the velocity field of the blue compact dwarf galaxy Mrk 86 (NGC 2537) using data provided by 14 long-slit optical spectra obtained in 10 different orientations and positions. This kinematical information is complemented with narrow-band ([O  iii ]5007 Å and H α ) and broad-band ( B , V , Gunn r and K ) imaging. The analysis of the galaxy global velocity field suggests that the ionized gas could be distributed in a rotating inclined disc, with projected central angular velocity of Ω=34 km s−1 kpc−1. The comparison between the stellar, H  i and modelled dark matter density profile indicates that the total mass within its optical radius is dominated by the stellar component. Peculiarities observed in its velocity field can be explained by irregularities in the ionized gas distribution or local motions induced by star formation.
Kinematical evidences for two expanding bubbles, Mrk 86–B and Mrk 86–C, are given. They show expanding velocities of 34 and 17 km s−1, H α luminosities of 3×1038 and 1.7×1039 erg s−1, and physical radii of 374 and 120 pc, respectively. The change in the [S  ii ]/H α , [N  ii ]/H α , [O  ii ]/[O  iii ] and [O  iii ]/H β line ratios with the distance to the bubble precursor suggests a diminution in the ionization parameter and, in the case of Mrk 86–B, an enhancement of the shock-excited gas emission. The optical–near-infrared colours of the bubble precursors are characteristic of low‐metallicity star‐forming regions (∼0.2 Z⊙) with burst strengths of about 1 per cent in mass.  相似文献   

14.
We present new spectroscopic observations of the southern radio galaxy         . Despite the flat-spectrum character of the radio emission from this source, our optical spectra show no sign of the broad permitted lines and non-stellar continuum characteristic of quasar nuclei and broad-line radio galaxies. However, the high-ionization forbidden lines, including [O  iii ] λλ 5007, 4959, are unusually broad for a narrow-line radio galaxy     , and are blueshifted by 600 km s−1 relative to the low-ionization lines such as [O  ii ] λλ 3726,3729. The [O  ii ] lines are also considerably narrower     than the [O  iii ] lines, and have a redshift consistent with that of the recently detected H  i 21-cm absorption-line system. Whereas the kinematics of the [O  iii ] emission lines are consistent with outflow in an inner narrow-line region, the properties of the [O  ii ] emission lines suggest that they are emitted by a more extended and quiescent gaseous component. We argue that, given the radio properties of the source, our line of sight is likely to be lying close to the direction of bulk outflow of the radio jets. In this case it is probable that the quasar nucleus is entirely obscured at optical wavelengths by the material responsible for the H  i absorption-line system. The unusually broad [O  iii ] emission lines suggest that the radio source is intrinsically compact. Overall, our data are consistent the idea that     is a radio source in an early stage of evolution.  相似文献   

15.
We present echelle spectrophotometry of the Galactic H  ii region S 311. The data have been taken with the Very Large Telescope Ultraviolet-Visual Echelle Spectrograph in the 3100–10 400 Å range. We have measured the intensities of 263 emission lines; 178 are permitted lines of H0, D0 (deuterium), He0, C0, C+, N0, N+, O0, O+, S+, Si0, Si+, Ar0 and Fe0; some of them are produced by recombination and others mainly by fluorescence. Physical conditions have been derived using different continuum- and line-intensity ratios. We have derived He+, C++ and O++ ionic abundances from pure recombination lines as well as abundances from collisionally excited lines for a large number of ions of different elements. We have obtained consistent estimations of t 2 applying different methods. We have found that the temperature fluctuations paradigm is consistent with the T e(He  i ) versus T e(H  i ) relation for H  ii regions, in contrast with what has been found for planetary nebulae. We report the detection of deuterium Balmer lines up to Dδ in the blue wings of the hydrogen lines, whose excitation mechanism seems to be continuum fluorescence.  相似文献   

16.
The magnetic-dipole probabilities for the 1D2–3P2 and 1D2–3P1 transitions in carbon-like and oxygen-like ions are calculated up to atomic number Z =12, including relativistic corrections to the magnetic dipole operator. The ratio of the probabilities for these two transitions is found to change by up to 5 per cent compared with previous theoretical work, none of which included these relativistic corrections, with the effect being largest for the near neutral ions. The transition probability ratio for the [O  iii ] 5007 and 4959 Å lines is found to be 3.01, implying an intensity ratio of 2.98, in significantly better agreement with the observed ratio than the earlier theoretical work.  相似文献   

17.
We present 21-cm H  i line observations of the blue compact dwarf galaxy NGC 1705. Previous optical observations show a strong outflow powered by an ongoing starburst dominating the H  ii morphology and kinematics. In contrast, most of the H  i lies in a rotating disc. An extraplanar H  i spur accounts for ∼8 per cent of the total H  i mass, and is possibly associated with the H  ii outflow. The inferred mass loss rate out of the core of the galaxy is significant, ∼0.2 − 2 M⊙ yr−1, but does not dominate the H  i dynamics. Mass model fits to the rotation curve show that the dark matter (DM) halo is dominant at nearly all radii and has a central density ρ0 ≈ 0.1 M⊙ pc−3: ten times higher than typically found in dwarf irregular galaxies, but similar to the only other mass-modelled blue compact dwarf, NGC 2915. This large difference strongly indicates that there is little evolution between dwarf irregular and blue compact dwarf types. Instead, dominant DM haloes may regulate the morphology of dwarf galaxies by setting the critical surface density for disc star formation. Neither our data nor catalogue searches reveal any likely external trigger to the starburst in NGC 1705.  相似文献   

18.
We present high-quality optical spectroscopic observations of the planetary nebula (PN) Hf 2-2. The spectrum exhibits many prominent optical recombination lines (ORLs) from heavy-element ions. Analysis of the H  i and He  i recombination spectrum yields an electron temperature of ∼900 K, a factor of 10 lower than given by the collisionally excited [O  iii ] forbidden lines. The ionic abundances of heavy elements relative to hydrogen derived from ORLs are about a factor of 70 higher than those deduced from collisionally excited lines (CELs) from the same ions, the largest abundance discrepancy factor (adf) ever measured for a PN. By comparing the observed O  ii λ4089/λ4649 ORL ratio to theoretical value as a function of electron temperature, we show that the O  ii ORLs arise from ionized regions with an electron temperature of only ∼630 K. The current observations thus provide the strongest evidence that the nebula contains another previously unknown component of cold, high-metallicity gas, which is too cool to excite any significant optical or ultraviolet CELs and is thus invisible via such lines. The existence of such a plasma component in PNe provides a natural solution to the long-standing dichotomy between nebular plasma diagnostics and abundance determinations using CELs on the one hand and ORLs on the other.  相似文献   

19.
Using simple stellar population synthesis, we model the bulge stellar contribution in the optical spectrum of a narrow-line Seyfert 1 galaxy, RE J1034+396. We find that its bulge stellar velocity dispersion is  67.7 ± 8 km s−1  . The supermassive black hole (SMBH) mass is about  (1–4) × 106 M⊙  if it follows the well-known   M BH–σ*  relation found in quiescent galaxies. We also derive the SMBH mass from the Hβ second moment, which is consistent with that from its bulge stellar velocity dispersion. The SMBH mass of (1–4)  × 106 M⊙  implies that the X-ray quasi-periodic oscillation (QPO) of RE J1034+396 can be scaled to a high-frequency QPO at 27–108 Hz found in Galactic black hole binaries with a  10-M⊙  black hole. With the mass distribution in different age stellar populations, we find that the mean specific star formation rate (SSFR) over the past 0.1 Gyr is  0.0163 ± 0.0011  Gyr−1, the stellar mass in the logarithm is  10.155 ± 0.06  in units of solar mass and the current star formation rate is  0.23 ± 0.016 M⊙ yr−1  . For RE J1034+396, there is no relation between the Eddington ratio and the SSFR as suggested by Chen et al., despite a larger scatter in their relation. We also suggest that about 7.0 per cent of the total Hα luminosity and 50 per cent of the total [O  ii ] luminosity come from the star formation process.  相似文献   

20.
We investigate the correlation between the supermassive black holes (SMBHs) mass ( M bh) and the stellar velocity dispersion  (σ*)  in two types of host galaxies: the early-type bulges (disc galaxies with classical bulges or elliptical galaxies) and pseudo-bulges. In the form  log ( M bh/M⊙) =α+β log (σ*/200 km s−1)  , the best-fitting results for the 39 early-type bulges are the slope  β= 4.06 ± 0.28  and the normalization  α= 8.28 ± 0.05  ; the best-fitting results for the nine pseudo-bulges are  β= 4.5 ± 1.3  and  α= 7.50 ± 0.18  . Both relations have intrinsic scatter in  log  M bh  of ≲0.27 dex. The   M bh–σ*  relation for pseudo-bulges is different from the relation in the early-type bulges over the 3σ significance level. The contrasting relations indicate the formation and growth histories of SMBHs depend on their host type. The discrepancy between the slope of the   M bh–σ*  relations using different definition of velocity dispersion vanishes in our sample, a uniform slope will constrain the coevolution theories of the SMBHs and their host galaxies more effectively. We also find the slope for the 'core' elliptical galaxies at the high-mass range of the relation appears steeper  (β≃ 5–6)  , which may be the imprint of their origin of dissipationless mergers.  相似文献   

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