In this paper, multi-wavelength data are compiled for a sample of 1425 Fermi blazars to calculate their spectral energy distributions (SEDs). A parabolic function, log(νF ν ) = P 1 (logν − P 2 ) 2 + P 3 , is used for SED fitting. Synchrotron peak frequency (logν p ), spectral curvature (P 1 ), peak flux (ν p F νp ), and integrated flux (νF ν ) are successfully obtained for 1392 blazars (461 flat spectrum radio quasarsFSRQs, 620 BL Lacs-BLs and 311 blazars of uncertain type-BCUs, 999 sources have known redshifts). Monochromatic luminosity at radio 1.4 GHz, optical R band, X-ray at 1 keV and γ-ray at 1 GeV, peak luminosity, integrated luminosity and effective spectral indexes of radio to optical (α RO ), and optical to X-ray (α OX ) are calculated. The "Bayesian classification" is employed to logν p in the rest frame for 999 blazars with available redshift and the results show that 3 components are enough to fit the logν p distribution, there is no ultra high peaked subclass. Based on the 3 components, the subclasses of blazars using the acronyms of Abdo et al. (2010a) are classified, and some mutual correlations are also studied. Conclusions are finally drawn as follows: (1) SEDs are successfully obtained for 1392 blazars. The fitted peak frequencies are compared with common sources from samples available ( Sambruna et al. 1996, Nieppola et al. 2006, 2008, Abdo et al. 2010a. (2) -2 -peak sources (ISPs) if 14.0 < log ν p (Hz) ≤ 15.3, and high synchrotron peak sources (HSPs) if log ν p (Hz) > 15.3. (3) γ-ray emissions are strongly correlated with radio emissions. γ-ray luminosity is also correlated with synchrotron peak luminosity and integrated luminosity. (4) There is an anti-correlation between peak frequency and peak luminosity within the whole blazar sample. However, there is a marginally positive correlation for HBLs, and no correlations for FSRQs or LBLs. (5) There are anti-correlations between the monochromatic luminosities (γ-ray and radio bands) and the peak frequency within the whole sample and BL Lacs. (6) The optical to X-ray (α OX ) and radio to optical (α RO ) spectral indexes are strongly anti-correlated with peak frequency (log ν p ) within the whole sample, but the correlations for subclasses of FSRQs, LBLs, and HBLs are different.

In Paper I, we presented spectrophotometric measurements of emission lines from the ultraviolet (UV) to the far‐infrared for 12 Galactic planetary nebulae (PNe) and derived nebular thermal and density structures using a variety of plasma diagnostics. The measurements and plasma diagnostic results are used in the current paper to determine elemental abundances in these nebulae. Abundance analyses are carried out using both strong collisionally excited lines (CELs) and weak optical recombination lines (ORLs) from heavy element ions. Assuming electron temperatures and densities derived from H i recombination spectra (line and continuum), we are able to determine the ORL C abundance relative to hydrogen for all the PNe in our sample, N and O abundances for 11 of them and Ne abundances for nine of them. In all cases, ORL abundances are found to be systematically higher than the corresponding values deduced from CELs. In NGC 40, the discrepancy between the abundances derived from the two types of emission line reaches a factor of 17 for oxygen. For the other 10 PNe, the discrepancies for oxygen vary from 1.6 to 3.1. In general, collisionally excited infrared fine‐structure lines, which have excitation energies less than 103 K and consequently emissivities that are insensitive to electron temperature and temperature fluctuations, yield ionic abundances comparable to those derived from optical/UV CELs. For a given nebula, the discrepancies between the ORL and CEL abundances are of similar magnitude for different elements. In other words, relative abundance ratios such as C/O, N/O and Ne/O deduced from the traditional method based on strong CELs are comparable to those yielded by ORLs, for a wide range of ORL to CEL oxygen abundance ratios, varying from near unity to over a factor of 20. We have also determined ORL abundances relative to hydrogen for the third‐row element magnesium for 11 nebulae in our sample. In strong contrast to the cases for second‐row elements, Mg abundances derived from the Mg ii 3d–4f λ4481 ORL are nearly constant for all the PNe analysed so far and agree within the uncertainties with the solar photospheric value. In accordance with results from previous studies, the ORL to CEL abundance ratio is correlated with the difference between the electron temperatures derived from the [O iii] forbidden‐line ratio, on the one hand, and from the hydrogen recombination Balmer discontinuity, on the other. We find that the discrepancy between the ORL and CEL abundances is correlated with nebular absolute diameter, surface brightness, the electron density derived from [S ii] CELs, and excitation class. The results confirm that the dichotomy of temperatures and heavy elemental abundances determined from the two types of emission line, which has been widely observed in PNe, is a strong function of nebular evolution, as first pointed out by Garnett and Dinerstein. Our analyses show that temperature fluctuations and/or density inhomogeneities are incapable of explaining the large discrepancies between the ...

A method is presented to derive electron temperatures and densities of planetary nebulae (PNe) simultaneously, using the observed hydrogen recombination spectrum, which includes continuum and line emission. By matching theoretical spectra to observed spectra around the Balmer jump at about 3646 Å, we determine electron temperatures and densities for 48 Galactic PNe. The electron temperatures based on this method – hereafter Te(Bal) – are found to be systematically lower than those derived from [O iii]λ4959/λ4363 and [O iii](88 μm + 52 μm)/λ4959 ratios – hereafter Te([O iii]na) and Te([O iii]fn). The electron densities based on this method are found to be systematically higher than those derived from [O ii]λ3729/λ3726, [S ii]λ6731/λ6716, [Cl iii]λ5537/λ5517, [Ar iv]λ4740/λ4711 and [O iii]88 μm/52 μm ratios. These results suggest that temperature and density fluctuations are generally present within nebulae. The comparison of Te([O iii]na) and Te(Bal) suggests that the fractional mean‐square temperature variation (t2) has a representative value of 0.031. A majority of temperatures derived from the Te([O iii]fn) ratio are found to be higher than those of Te([O iii]na), which is attributed to the existence of dense clumps in nebulae – those [O iii] infrared fine‐structure lines are suppressed by collisional de‐excitation in the clumps. By comparing Te([O iii]fn), Te([O iii]na) and Te(Bal) and assuming a simple two‐density‐component model, we find that the filling factor of dense clumps has a representative value of 7 × 10−5. The discrepancies between Te([O iii]na) and Te(Bal) are found to be anticorrelated with electron densities derived from various density indicators; high‐density nebulae have the smallest temperature discrepancies. This suggests that temperature discrepancy is related to nebular evolution. In addition, He/H abundances of PNe are found to be positively correlated with the difference between Te([O iii]na) and Te(Bal), suggesting that He/H abundances might have been overestimated generally because of the possible existence of H‐deficient knots. Electron temperatures and densities deduced from spectra around the Paschen jump regions at 8250 Å are also obtained for four PNe: NGC 7027, NGC 6153, M 1–42 and NGC 7009. Electron densities derived from spectra around the Paschen jump regions are in good agreement with the corresponding values derived from spectra around the Balmer jump, whereas temperatures deduced from the spectra around the Paschen jump are found to be lower than the corresponding values derived from spectra around the Balmer jump for all the four cases. The reason remains unclear.