اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدSuper-Eddington accretion rates in Narrow Line Seyfert 1 galaxies
87
0
0.0
(
0
)
تأليف
S. Collin
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Using the BH masses deduced from the empirical relation of Kaspi et al. (2000) and assuming that the optical luminosity is provided by the accretion disc, we show that Narrow Line Seyfert Galaxies 1 (NLS1s) accrete at super-Eddington rates, while their luminosity stays of the order of the Eddington limit. We take into account the possibility of a non-viscous energy release in the gravitationally unstable region of the disc. It leads to a smaller accretion rate and to a redder continuum than a standard disc, which agrees better with the observations. The observed bolometric luminosities appear to saturate at a few times the Eddington luminosity for super-Eddington accretion rates, as predicted by slim disc models. The accretion rate stays always of the order of a few M$_{odot}$/yr, indicating that the growing of the BH is mass supply limited . Since the masses of the BH increases by one order of magnitude in a few 10$^7$ years, it could explain why NLS1s appear to not follow the same BH - bulge relation as other galaxies. NLS1s should thus play an important role in shaping the mass function of local BHs. We discuss the possibility that the masses could be systematically underestimated due to an inclination effect, and we conclude that the accretion rates could thus be strongly overestimated, but only in a small proportion of objects.
قيم البحث
اقرأ أيضاً
I provide a short review of the properties of Narrow-line Seyfert 1 (NLS1) galaxies across the electromagnetic spectrum and of the models to explain them. Their continuum and emission-line properties manifest one extreme form of Seyfert activity. As
such, NLS1 galaxies may hold important clues to the key parameters that drive nuclear activity. Their high accretion rates close to the Eddington rate provide new insight into accretion physics, their low black hole masses and perhaps young ages allow us to address issues of black hole growth, their strong optical FeII emission places strong constraints on FeII and perhaps metal formation models and physical conditions in these emission-line clouds, and their enhanced radio quiteness permits a fresh look at causes of radio loudness and the radio-loud radio-quiet bimodality in AGN.
This work studies the optical emission line properties and physical conditions of the narrow line region (NLR) of seven narrow-line Seyfert 1 galaxies (NLS1). Our results show that the flux carried out by the narrow component of H-beta is, on average
, 50% of the total line flux. As a result, the [OIII] 5007/H-beta ratio emitted in the NLR varies from 1 to 5, instead of the universally adopted value of 10. This has strong implications for the required spectral energy distribution that ionizes the NLR gas. Photoionization models that consider a NLR composed of a combination of matter-bounded and ionization-bounded clouds are successful at explaining the low [OIII] 5007/H-beta ratio and the weakness of low-ionization lines of NLS1s. Variation of the relative proportion of these two type of clouds nicely reproduce the dispersion of narrow line ratios found among the NLS1 sample. Assuming similar physical model parameters of both NLS1s and the normal Seyfert 1 galaxy NGC 5548, we show that the observed differences of emission line ratios between these two groups can be explained in terms of the shape of the input ionizing continuum. Narrow emission line ratios of NLS1s are better reproduced by a steep power-law continuum in the EUV -- soft X-ray region, with spectral index alpha ~ -2. Flatter spectral indices (alpha ~ -1.5) match the observed line ratios of NGC 5548 but are unable to provide a good match to the NLS1 ratios. This result is consistent with ROSAT observations of NLS1s, which show that these objects are characterized by steeper power-law indices than those of Sy1 galaxies with strong broad optical lines.
Narrow line Seyfert 1 (NLSy1) galaxies constitute a class of active galactic nuclei characterized by the full width at half maximum (FWHM) of the H$beta$ broad emission line < 2000 km/s and the flux ratio of [O III] to H$beta$ < 3. Their properties a
re not well understood since only a few NLSy1 galaxies were known earlier. We have studied various properties of NLSy1 galaxies using an enlarged sample and compared them with the conventional broad-line Seyfert 1 (BLSy1) galaxies. Both the sample of sources have z $le$ 0.8 and their optical spectra from SDSS-DR12 that are used to derive various physical parameters have a median signal to noise (S/N) ratio >10 per pixel. Strong correlations between the H$beta$ and H$alpha$ emission lines are found both in the FWHM and flux. The nuclear continuum luminosity is found to be strongly correlated with the luminosity of H$beta$, H$alpha$ and [O III] emission lines. The black hole mass in NLSy1 galaxies is lower compared to their broad line counterparts. Compared to BLSy1 galaxies, NLSy1 galaxies have a stronger FeII emission and a higher Eddington ratio that place them in the extreme upper right corner of the $R_{4570}$ - $xi_{Edd}$ diagram. The distribution of the radio-loudness parameter (R) in NLSy1 galaxies drops rapidly at R > 10 compared to the BLSy1 galaxies that have powerful radio jets. The soft X-ray photon index in NLSy1 galaxies is on average higher (2.9 $pm$ 0.9) than BLSy1 galaxies (2.4 $pm$ 0.8). It is anti-correlated with the H$beta$ width but correlated with the Fe II strength. NLSy1 galaxies on average have a lower amplitude of optical variability compared to their broad lines counterparts. These results suggest Eddington ratio as the main parameter that drives optical variability in these sources.
In this paper, we explore the physics of the accretion and jet in narrow-line Seyfert 1 galaxies (NLS1). Specifically, we compile a sample composed of 16 nearby NLS1 with $L_{rm bol}/L_{rm Edd} gtrsim 0.1$. We investigate the mutual correlation betwe
en their radio luminosity $L_{rm R}$, X-ray luminosity $L_{rm X}$, optical luminosity $L_{rm 5100}$ and black hole mass $M_{rm BH}$. By adopting partial correlation analysis: (1) we find a positive correlation between $L_{rm X}$ and $M_{rm BH}$, and (2) we find a weak positive correlation between $L_{rm R}$ and $L_{5100}$. However, we dont find significant correlations between $L_{rm R}$ and $L_{rm X}$ or between $L_{rm X}$ and $L_{5100}$ after considering the effect of the black hole mass, which leads to a finding of the independence of $L_{rm X}/L_{rm Edd}$ on $L_{5100}/L_{rm Edd}$. Interestingly, the findings that $L_{rm X}$ is correlated with $M_{rm BH}$ and $L_{rm X}/L_{rm Edd}$ is not correlated with $L_{5100}/L_{rm Edd}$ support that the X-ray emission is saturated with increasing $dot{M}$ for $L_{rm bol}/L_{rm Edd} gtrsim 0.1$ in NLS1s, which may be understood in the framework of slim disc scenario. Finally, we suggest that a larger NLS1 sample with high quality radio and X-ray data is needed to further confirm this result in the future.
We present optical images of nearby 50 narrow-line Seyfert 1 galaxies (NLS1s) which cover all the NLS1s at z<0.0666 and $delta ge -25^{circ}$ known at the time of 2001. Among the 50 NLS1s, 40 images are newly obtained by our observations and 10 image
s are taken from archive data. Motivated by the hypothesis that NLS1s are in an early phase of a super-massive black hole (BH) evolution, we present a study of NLS1 host galaxy morphology to examine trigger mechanism(s) of active galactic nuclei (AGNs) by seeing the early phase of AGN. With these images, we made morphological classification by eye inspection and by quantitative method, and found a high bar frequency of the NLS1s in the optical band; the bar frequency is $85 pm 7% among disk galaxies ($64- 71$% in total sample) which is more frequent than that (40-70%) of broad-line Seyfert 1 galaxies (BLS1s) and normal disk galaxies, though the significance is marginal. Our results confirm the claim by Crenshaw et al. (2003) with a similar analysis for 19 NLS1s. The frequency is comparable to that of HII/starburst galaxies. We also examined the bar frequency against width of the broad H$beta$ emission line, Eddington ratio, and black hole mass, but no clear trend is seen. Possible implications such as an evolutionary sequence from NLS1s to BLS1 are discussed briefly.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
