Abstract
We present an analysis of multiwavelength observations of the dark globule DC 314.8–5.1, using data from the Gaia optical, Two Micron All Star Survey near-infrared, and Wide-field Infrared ...Survey Explorer mid-infrared surveys, dedicated imaging with the Spitzer Space Telescope, and X-ray data obtained with the Swift X-Ray Telescope (XRT). The main goal was to identify possible pre-main-sequence stars (PMSs) and young stellar objects (YSOs) associated with the globule. For this, we studied the infrared colors of all point sources within the boundaries of the cloud. After removing sources with nonstellar spectra, we investigated the Gaia parallaxes for the YSO candidates and found that none are physically related to DC 314.8–5.1. In addition, we searched for X-ray emission from PMSs with Swift-XRT, and found no 0.5–10 keV emission down to a luminosity level ≲10
31
erg s
−1
, typical of a PMS with mass ≥2
M
⊙
. Our detailed inspection therefore supports a very young, “prestellar core” evolutionary stage for the cloud. Based on archival Planck and IRAS data, we moreover identify the presence of hot dust, with temperatures ≳100 K, in addition to the dominant dust component at 14 K, originating with the associated reflection nebula.
Here we discuss the jet production efficiency in a sample of 17 young radio galaxies with measured redshifts, kinematic ages, and nuclear X-ray fluxes, for which the observed luminosities of compact ...jets/lobes and accretion disks correspond to the same episode of AGN activity. For the targets, we analyze the available optical data, estimating the bolometric luminosities of the accretion disks Lbol, and the black hole masses; we also derive the minimum jet kinetic luminosities, Pj. With this information we investigate the distribution of our sample in the three-dimensional space of the accretion rate λEdd Lbol/LEdd, the nuclear X-ray luminosity LX considered here as a limit for the emission of the disk coronae, and Pj, expressing the latter two parameters either in the Eddington units, or in the units of the disk luminosity. We find that (i) the accretion rate λEdd in our sample is distributed within a narrow range λEdd ∼ 0.01-0.2; (ii) the normalized jet power Pj/LEdd formally correlates with the accretion rate λEdd, with some saturation at the largest values λEdd > 0.05; (iii) the jet production efficiency spans a range from jet 10−3 up to ∼0.2 at maximum, which is below the level expected for magnetically arrested disks around maximally spinning black holes; and (iv) there is a diversification in jet on the hardness-intensity diagram LX/Lbol − λEdd, with the jets being produced most efficiently during the high/hard states, and suppressed during the soft states.
Abstract
We present an analysis of the mid-infrared spectra, obtained from the Spitzer Space Telescope, of the dark globule DC 314.8–5.1, which is at the onset of low-mass star formation. The target ...has a serendipitous association with a B-type field star that illuminates a reflection nebula in the cloud. We focus on the polycyclic aromatic hydrocarbon (PAH) emission features prevalent throughout the mid-infrared range. The analysis of the spectra with the PAHFIT software as well as with the pypahdb package shows that (i) the intensities of PAH features decrease over distance from the ionizing star toward the cloud center, with some however showing a saturation at larger distances; (ii) the relative intensities of the 6.2 and 8.6 features with respect to the 11.2
μ
m feature remain high throughout the globule, suggesting a higher cation-to-neutral PAH ratio of the order of unity; the breakdown from pypahdb confirms a high ionized fraction within the cloud; (iii) the pypahdb results display a decrease in large-PAH fraction with increased distance from HD 130079, as well as a statistically significant correlation between the large-size fraction and the ionized fraction across the globule; (iv) the 7.7 PAH feature displays a peak nearer to 7.8
μ
m, suggesting a chemically processed PAH population with a small fraction of UV-processed PAHs; and (v) the H
2
S(0) line is detected at larger distances from the ionizing star. All in all, our results suggest divergent physical conditions within the quiescent cloud DC 314.8–5.1 as compared to molecular clouds with ongoing star formation.
We present a systematic analysis of the mid-infrared (MIR) properties of the youngest radio galaxies, based on low-resolution data provided by the Wide-field Infrared Survey Explorer and IRAS ...satellites. We restrict our analysis to sources with available X-ray data that constitute the earliest phase of radio galaxy evolution, i.e., those classified as gigahertz-peaked spectrum and/or compact symmetric objects. In our sample of 29 objects, we find that the host galaxies are predominantly red/yellow ellipticals, with some of them displaying distorted morphology. We find a variety of MIR colors and observe that the sources in which the MIR emission is dominated by the ISM component uniformly populate the region occupied by galaxies with a wide range of pronounced (≥0.5M yr−1) star formation activity. We compare the MIR color distribution in our sample to that in the general population of local active galactic nuclei (AGNs), in the population of evolved FR II radio galaxies, and also in the population of radio galaxies with recurrent jet activity. We conclude that the triggering of radio jets in AGNs does not differentiate between elliptical hosts with substantially different fractions of young stars; instead, there is a relationship between the jet duty cycle and the ongoing star formation. The distribution of the subsample of our sources with z < 0.4 on the low-resolution MIR versus absorption-corrected X-ray luminosity plane is consistent with the distribution of a sample of local AGNs. Finally, we comment on the star formation rates of the two γ-ray-detected sources in our sample, 1146+596 and 1718-649.
We present an analysis of the new, deep (94 ksec) Chandra ACIS-S observation of radio-loud active galaxy CGCG 292−057, characterized by a LINER-type nucleus and a complex radio structure that ...indicates intermittent jet activity. On the scale of the host galaxy bulge, we detected excess X-ray emission with a spectrum best fit by a thermal plasma model with a temperature of ∼0.8 keV. We argue that this excess emission results from compression and heating of the hot diffuse fraction of the interstellar medium displaced by the expanding inner, ∼20 kpc-scale lobes observed in this restarted radio galaxy. The nuclear X-ray spectrum of the target clearly displays an ionized iron line at ∼6.7 keV, and is best fitted with a phenomenological model consisting of a power-law (photon index 1.8) continuum absorbed by a relatively large amount of cold matter (hydrogen column density 0.7 × 1023 cm−2), and partly scattered (fraction ∼3%) by ionized gas, giving rise to a soft excess component and K line from iron ions. We demonstrate that the observed X-ray spectrum, particularly the equivalent width of Fe XXV K (of order 0.3 keV) can in principle, be explained in a scenario involving a Compton-thin gas located at the scale of the broad-lined region in this source and photoionized by nuclear illumination. We compare the general spectral properties of the CGCG 292−057 nucleus, with those of other nearby LINERs studied in X-rays.
Abstract
Here we present a systematic analysis of the mid-infrared properties of young radio galaxies, based on lower-resolution data provided by WISE and IRAS satellites. We restrict our analysis to ...sources in the earliest phase of radio galaxy evolution, with corresponding ages of the radio structures ≤ 3,000 yrs. In our sample of 29 objects, we find a variety of WISE colors, which suggests that the mid-infrared continua of studied sources are not exclusively contributed to by the circumnuclear dust. A comparison of the total mid-infrared and absorption-corrected X-ray luminosities for our sample reveals a clear correlation between the two bands. This favors the scenario in which the observed X-ray emission of young radio galaxies — at least the high-luminosity ones — originates predominantly in accretion disk corona.
We present an analysis of multi-wavelength observations of the dark globule DC\,314.8--5.1, using data from the Gaia optical, 2MASS near-infrared, and WISE mid-infrared surveys, dedicated imaging ...with the Spitzer Space Telescope, and X-ray data obtained with the Swift-XRT Telescope (XRT). The main goal was to identify possible pre-main sequence stars (PMSs) and young stellar objects (YSOs) associated with the globule. For this, we studied the infrared colors of all point sources within the boundaries of the cloud. After removing sources with non-stellar spectra, we investigated the Gaia parallaxes for the YSO candidates, and found that none are physically related to DC\,314.8--5.1. In addition, we searched for X-ray emission from pre-main sequence stars with Swift-XRT, and found no 0.5--10\,keV emission down to a luminosity level \(\lesssim 10^{31}\)erg\,s\(^{-1}\), typical of a PMS with mass\,\(\ge 2 M_\odot\). Our detailed inspection therefore supports a very young, ``pre-stellar core'' evolutionary stage for the cloud. Based on archival Planck and IRAS data, we moreover identify the presence of hot dust, with temperatures \(\gtrsim 100\)\,K, in addition to the dominant dust component at 14\,K, originating with the associated reflection nebula.
We present an analysis of the mid-infrared spectra, obtained from the Spitzer Space Telescope, of the dark globule, DC 314.8--5.1, which is at the onset of low-mass star formation. The target has a ...serendipitous association with a B-type field star, which illuminates a reflection nebula in the cloud. We focus on the polycyclic aromatic hydrocarbon (PAH) emission features prevalent throughout the mid-infrared range. The analysis of the spectra with the PAHFIT software as well as pypahdb package, shows that (i) the intensities of PAH features decrease over distance from the ionizing star toward the cloud center, some however showing a saturation at larger distances; (ii) the relative intensities of the 6.2 and 8.6 features with respect to the 11.2 micron feature remain high throughout the globule, suggesting a larger cation-to-neutral PAH ratio of the order of unity; the breakdown from pypahdb confirms a high ionized fraction within the cloud; (iii) the pypahdb results display a decrease in large PAH fraction with increased distance from HD 130079, as well as a statistically significant correlation between the large size fraction and the ionized fraction across the globule; (iv) the 7.7 PAH feature displays a peak nearer to 7.8 microns, suggesting a chemically processed PAH population with a small fraction of UV-processed PAHs; (v) the H2 S(0) line is detected at larger distances from the ionizing star. All in all, our results suggest divergent physical conditions within the quiescent cloud DC 314.8--5.1 as compared to molecular clouds with ongoing starformation.
Here we discuss the jet production efficiency in a sample of 17 young radio galaxies with measured redshifts, kinematic ages, and nuclear X-ray fluxes, for which the observed luminosities of compact ...jets/lobes and accretion disks correspond to the same episode of the AGN activity. For the targets, we analyze the available optical data, estimating the bolometric luminosities of the accretion disks \(L_{\rm bol}\), and the black hole masses; we also derive the minimum jet kinetic luminosities, \(P_{\rm j}\). With such, we investigate the distribution of our sample in the three-dimensional space of the accretion rate \(\lambda_{\rm Edd} \equiv L_{\rm bol}/L_{\rm Edd}\), the nuclear X-ray luminosity \(L_{\rm X}\) considered here as a limit for the emission of the disk coronae, and \(P_{\rm j}\), expressing the latter two parameters either in the Eddington units, or in the units of the disk luminosity. We find that (i) the accretion rate \(\lambda_{\rm Edd}\) in our sample is distributed within a narrow range \(\lambda_{\rm Edd} \sim 0.01 - 0.2\); (ii) the normalized jet power \(P_{\rm j}/L_{\rm Edd}\) formally correlates with the accretion rate \(\lambda_{\rm Edd}\), with some saturation at the largest values \(\lambda_{\rm Edd}> 0.05\); (iii) the jet production efficiency \(\eta_{\rm jet} \equiv P_{\rm j}/\dot{M}_{\rm acc} c^2\) spans a range from \(\eta_{\rm jet} \lesssim 10^{-3}\) up to \(\sim 0.2\) at maximum, which is below the level expected for magnetically arrested disks around maximally spinning black holes; and (iv) there is a diversification in \(\eta_{\rm jet}\) on the hardness--intensity diagram \(L_{\rm X}/L_{\rm bol} - \lambda_{\rm Edd}\), with the jets being produced most efficiently during the high/hard states, and suppressed during the soft states.
We present an analysis of the new, deep (94\,ksec) {\it Chandra} ACIS-S observation of radio-loud active galaxy CGCG\,292\(-\)057, characterized by a LINER-type nucleus and a complex radio structure ...that indicates intermittent jet activity. On the scale of the host galaxy bulge, we detected excess X-ray emission with a spectrum best fit by a thermal plasma model with a temperature of \(\sim 0.8\)\,keV. We argue that this excess emission results from compression and heating of the hot diffuse fraction of the interstellar medium displaced by the expanding inner, \(\sim 20\)\, kpc-scale lobes observed in this restarted radio galaxy. The nuclear X-ray spectrum of the target clearly displays an ionized iron line at \(\sim 6.7\)\,keV, and is best fitted with a phenomenological model consisting of a power-law (photon index \(\simeq 1.8\)) continuum absorbed by a relatively large amount of cold matter (hydrogen column density \(\simeq 0.7 \times 10^{23}\)\,cm\(^{-2}\)), and partly scattered (fraction \(\sim 3\%\)) by ionized gas, giving rise to a soft excess component and K\(\alpha\) line from iron ions. We demonstrate that the observed X-ray spectrum, particularly the equivalent width of Fe\,\texttt{XXV} K\(\alpha\) (of order \(0.3\)\,keV) can in principle, be explained in a scenario involving a Compton-thin gas located at the scale of the broad-lined region in this source and photoionized by nuclear illumination. We compare the general spectral properties of the CGCG\,292\(-\)057 nucleus, with those of other nearby LINERs studied in X-rays.
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