- ID:
- ivo://CDS.VizieR/J/ApJS/224/5
- Title:
- The Herschel Orion Protostar Survey (HOPS): SEDs
- Short Name:
- J/ApJS/224/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present key results from the Herschel Orion Protostar Survey (HOPS): spectral energy distributions (SEDs) and model fits of 330 young stellar objects, predominantly protostars, in the Orion molecular clouds. This is the largest sample of protostars studied in a single, nearby star formation complex. With near-infrared photometry from 2MASS, mid- and far-infrared data from Spitzer and Herschel, and submillimeter photometry from APEX, our SEDs cover 1.2-870{mu}m and sample the peak of the protostellar envelope emission at ~100{mu}m. Using mid-IR spectral indices and bolometric temperatures, we classify our sample into 92 Class 0 protostars, 125 Class I protostars, 102 flat-spectrum sources, and 11 Class II pre-main-sequence stars. We implement a simple protostellar model (including a disk in an infalling envelope with outflow cavities) to generate a grid of 30400 model SEDs and use it to determine the best-fit model parameters for each protostar. We argue that far-IR data are essential for accurate constraints on protostellar envelope properties. We find that most protostars, and in particular the flat-spectrum sources, are well fit. The median envelope density and median inclination angle decrease from Class 0 to Class I to flat-spectrum protostars, despite the broad range in best-fit parameters in each of the three categories. We also discuss degeneracies in our model parameters. Our results confirm that the different protostellar classes generally correspond to an evolutionary sequence with a decreasing envelope infall rate, but the inclination angle also plays a role in the appearance, and thus interpretation, of the SEDs.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/187/64
- Title:
- The simultaneous optical-to-X-ray SED of AGNs
- Short Name:
- J/ApJS/187/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report Swift observations of a sample of 92 bright soft X-ray selected active galactic nuclei (AGNs). This sample represents the largest number of AGNs observed to study the spectral energy distribution (SED) of AGNs with simultaneous optical/UV and X-ray data. The principal motivation of this study is to understand the SEDs of AGNs in the optical/UV to X-ray regime and to provide bolometric corrections which are important in determining the Eddington ratio L/L_Edd_. In particular, we rigorously explore the dependence of the UV-EUV contribution to the bolometric correction on the assumed EUV spectral shape. We find strong correlations of the spectral slopes {alpha}_X_ and {alpha}_UV_ with L/L_Edd_.
- ID:
- ivo://CDS.VizieR/J/MNRAS/456/790
- Title:
- TP-AGB stars contribution in SFR
- Short Name:
- J/MNRAS/456/790
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the debated contribution from thermally pulsing asymptotic-giant-branch (TP-AGB) stars in evolutionary population synthesis models. We investigate the spectral energy distributions (SEDs) of a sample of 51 spectroscopically confirmed, high-z (1.3<z_spec_<2.7), galaxies using three evolutionary population synthesis models with strong, mild and light TP-AGB. Our sample is the largest of spectroscopically confirmed galaxies on which such models are tested so far. Galaxies were selected as passive, but we model them using a variety of star formation histories in order not to be dependent on this pre-selection. We find that the observed SEDs are best fitted with a significant contribution of TP-AGB stars or with substantial dust attenuation. Without including reddening, TP-AGB-strong models perform better and deliver solutions consistent within 1{sigma} from the best-fitted ones in the vast majority of cases. Including reddening, all models perform similarly. Using independent constraints from observations in the mid- and far-IR, we show that low/negligible dust attenuation, i.e. E(B-V)<~0.05, should be preferred for the SEDs of passively selected galaxies. Given that TP-AGB-light models give systematically older ages for passive galaxies, we suggest number counts of passive galaxies at higher redshifts as a further test to discriminate among stellar population models.
- ID:
- ivo://CDS.VizieR/J/A+A/604/A48
- Title:
- UBVRI photometry and line fluxes of AG Peg
- Short Name:
- J/A+A/604/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- AG Peg is known as the slowest symbiotic nova, which experienced its nova-like outburst around 1850. After 165 years, during June of 2015, it erupted again showing characteristics of the Z And-type outburst. The primary objective is to determine basic characteristics, the nature and type of the 2015 outburst of AG Peg. We achieved this aim by modelling the spectral energy distribution using low-resolution spectroscopy (330-750nm), medium-resolution spectroscopy (420-720nm; R=11000), and UBVR_C_I_C_ photometry covering the 2015 outburst with a high cadence. Optical observations were complemented with the archival HST and FUSE spectra from the preceding quiescence. During the outburst, the luminosity of the hot component was in the range of 2-11x10^37^(d/0.8kpc})^2^erg/s. To generate the maximum luminosity the white dwarf (WD) had to accrete at ~3x10^-7^M_{sun}/yr, which exceeds the stable-burning limit and thus led to blowing optically thick wind from the WD. We determined its mass-loss rate to a few x10^-6^M_{sun}/yr. At the high temperature of the ionising source, 1.5-2.3x10^5^K, the wind converted a fraction of the WD's photospheric radiation into the nebular emission that dominated the optical. A one order of magnitude increase of the emission measure, from a few x10^59^(d/0.8kpc)^2^/cm^3^ during quiescence, to a few x10^60^(d/0.8kpc)^2^/cm^3^ during the outburst, caused a 2mag brightening in the LC, which is classified as the Z And-type of the outburst. The very high nebular emission and the presence of a disk-like HI region encompassing the WD, as indicated by a significant broadening and high flux of the Raman-scattered OVI 6825{AA} line during the outburst, is consistent with the ionisation structure of hot components in symbiotic stars during active phases.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A195
- Title:
- Unknown active galactic nuclei study
- Short Name:
- J/A+A/647/A195
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We collect data at all frequencies for the new sources classified as unknown active galactic nuclei (AGNs) in the latest Burst Alert Telescope all-sky hard X-ray catalog. Focusing on the 36 sources with measured redshift, we compute their spectral energy distribution (SED) from radio to {gamma}-rays with the aim to classify these objects. We apply emission models that attempt to reproduce the obtained SEDs, including: (i) a standard thin accretion disk together with an obscuring torus and a X-ray corona; (ii) a two temperature thick advection-dominated flow; (iii) an obscured AGN model, accounting for absorption along the line of sight at kiloelectronvolt energies and in the optical band; and (iv) a phenomenological model to describe the jet emission in blazar-like objects. We integrate the models with the SWIRE template libraries to account for the emission of the host galaxy. For every source we found a good agreement between data and our model. Considering that the sources were selected in the hard X-ray band, which is rather unaffected by absorption, we expected and found a large fraction of absorbed radio-quiet AGNs (31 out of 36) and some additional rare radio-loud sources (5 out of 36), since the jet emission in hard X-rays is important for aligned jets owing to the boost produced by the beaming effect. With our work we can confirm the hypothesis that a number of galaxies, whose optical spectra lack AGN emission features, host an obscured active nucleus. The approach we used proved to be efficient in rapidly identifying objects, which commonly used methods were not able to classify.
- ID:
- ivo://CDS.VizieR/J/A+A/317/712
- Title:
- UV fluxes and electron density of AG Peg
- Short Name:
- J/A+A/317/712
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we study in detail the variability of the symbiotic nova AG Peg in the IUE range during the period 1978-1995. We find that the luminosity of the hot component decreased steadily from about 1850L_{sun}_ in 1978 to 430L_{sun}_ in 1995 while its effective temperature remained nearly constant, 86500+/-1300K. At the same time, the mass loss rate decreased by a factor of 4-5 although the ejection velocity remained constant. The observed fainting of both the narrow and the broad emission lines is ascribed to the decrease of the luminosity and ionizing flux from the hot source. The narrow emission lines and the long wavelength UV continuum show periodic variations arising from a dense and asymmetric nebular region associated with the cool star. Radial velocity variations of the narrow lines indicate that this region is receding from the center of mass of the system, and support the presence of the ablation tail suggested by Penston and Allen (1985MNRAS.212..939P). No periodic flux variations are seen in the short wavelength ultraviolet continuum and in the broad emission lines, which are both formed in the fast wind from the hot component.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A58
- Title:
- Variability of the adiabatic parameter
- Short Name:
- J/A+A/616/A58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Numerical models of the evolution of interstellar and intergalactic plasmas often assume that the adiabatic parameter {gamma} (the ratio of the specific heats) is constant (5/3 in monoatomic plasmas). However, {gamma} is determined by the total internal energy of the plasma, which depends on the ionic and excitation state of the plasma. Hence, the adiabatic parameter may not be constant across the range of temperatures available in the interstellar medium. We aim to carry out detailed simulations of the thermal evolution of plasmas with Maxwell-Boltzmann and non-thermal ({kappa} and n) electron distributions in order to determine the temperature variability of the total internal energy and of the adiabatic parameter. The plasma, composed of H, He, C, N, O, Ne, Mg, Si, S, and Fe atoms and ions, evolves under collisional ionization equilibrium conditions, from an initial temperature of 10^9^K. The calculations include electron impact ionization, radiative and dielectronic recombinations and line excitation. The ionization structure was calculated solving a system of 112 linear equations using the Gauss elimination method with scaled partial pivoting. Numerical integrations used in the calculation of ionization and excitation rates are carried out using the double-exponential over a semi-finite interval method. In both methods a precision of 10^-15^ is adopted. The total internal energy of the plasma is mainly dominated by the ionization energy for temperatures lower than 8x10^4^K with the excitation energy having a contribution of less than one percent. In thermal and non-thermal plasmas composed of H, He, and metals, the adiabatic parameter evolution is determined by the H and He ionizations leading to a profile in general having three transitions. However, for {kappa} distributed plasmas these three transitions are not observed for {kappa<15} and for {kappa<5} there are no transitions. In general, {gamma} varies from 1.01 to 5/3. Lookup tables of the {gamma} parameter are presented as supplementary material.
- ID:
- ivo://CDS.VizieR/J/ApJS/243/15
- Title:
- WERGS. II. SED fitting with optical, IR & radio data
- Short Name:
- J/ApJS/243/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present physical properties of radio galaxies (RGs) with f_1.4GHz_>1mJy discovered by Subaru Hyper Suprime-Cam (HSC) and Very Large Array Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey. For 1056 FIRST RGs at 0<z<=1.7 with HSC counterparts in about 100deg^2^, we compiled multi-wavelength data of optical, near-infrared (IR), mid-IR, far-IR, and radio (150MHz). We derived their color excess (E(B-V)_*_), stellar mass, star formation rate (SFR), IR luminosity, the ratio of IR and radio luminosity (q_IR_), and radio spectral index ({alpha}_radio_) that are derived from the spectral energy distribution (SED) fitting with CIGALE. We also estimated Eddington ratio based on stellar mass and integration of the best-fit SEDs of active galactic nucleus (AGN) component. We found that E(B-V)_*_, SFR, and IR luminosity clearly depend on redshift while stellar mass, q_IR_, and {alpha}_radio_ do not significantly depend on redshift. Since optically faint (i_AB_>=21.3) RGs that are newly discovered by our RG survey tend to be high redshift, they tend to not only have a large dust extinction and low stellar mass but also have high SFR and AGN luminosity, high IR luminosity, and high Eddington ratio compared with optically bright ones. The physical properties of a fraction of RGs in our sample seem to differ from a classical view of RGs with massive stellar mass, low SFR, and low Eddington ratio, demonstrating that our RG survey with HSC and FIRST provides us curious RGs among entire RG population.
- ID:
- ivo://CDS.VizieR/J/ApJ/805/90
- Title:
- WISE ELIRGs and comparison with QSOs
- Short Name:
- J/ApJ/805/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 20 Wide-field Infrared Survey Explorer (WISE)-selected galaxies with bolometric luminosities L_bol_>10^14^L_{sun}_, including five with infrared luminosities L_IR_{equiv}L_(rest8-1000{mu}m)_>10^14^L_{sun}_. These "extremely luminous infrared galaxies", or ELIRGs, were discovered using the "W1W2-dropout" selection criteria which requires marginal or non-detections at 3.4 and 4.6{mu}m (W1 and W2, respectively) but strong detections at 12 and 22{mu}m in the WISE survey. Their spectral energy distributions are dominated by emission at rest-frame 4-10{mu}m, suggesting that hot dust with T_d_~450K is responsible for the high luminosities. These galaxies are likely powered by highly obscured active galactic nuclei (AGNs), and there is no evidence suggesting these systems are beamed or lensed. We compare this WISE-selected sample with 116 optically selected quasars that reach the same L_bol_ level, corresponding to the most luminous unobscured quasars in the literature. We find that the rest-frame 5.8 and 7.8{mu}m luminosities of the WISE-selected ELIRGs can be 30%-80% higher than that of the unobscured quasars. The existence of AGNs with L_bol_>10^14^L_{sun}_ at z>3 suggests that these supermassive black holes are born with large mass, or have very rapid mass assembly. For black hole seed masses ~10^3^M_{sun}_, either sustained super-Eddington accretion is needed, or the radiative efficiency must be <15%, implying a black hole with slow spin, possibly due to chaotic accretion.
- ID:
- ivo://CDS.VizieR/J/A+A/539/A48
- Title:
- XMM AGN optical-UV luminosities
- Short Name:
- J/A+A/539/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Active galactic nuclei (AGN) emit radiation over a wide range of wavelengths, with a peak of emission in the far-UV region of the electromagnetic spectrum, a spectral region that is historically difficult to observe. Using optical, GALEX UV, and XMM-Newton data we derive the spectral energy distribution (SED) from the optical/UV to X-ray regime of a sizeable sample of AGN. The principal motivation is to investigate the relationship between the optical/UV emission and the X-ray emission and provide bolometric corrections to the hard X-ray (2-10keV) energy range, k_bol_, the latter being a fundamental parameter in current physical cosmology.
