Optical Emission-line Luminosities Research Articles

Optical emission-line luminosity function models for populations of supernova remnants

ABSTRACT We present a basic model for the calculation of the luminosity distribution of supernova remnant populations. We construct theoretical H$\rm \alpha \,$and joint [S ii]-H$\rm \alpha \,$luminosity functions for supernova remnants by combining prescriptions from a basic evolution model that provides the shock velocity and radius for SNRs of different age and pre-shock density, with shock excitation models that give the gas emissivity for shocks of different physical parameters. We assume a flat age distribution, and we explore the effect of different pre-shock density distributions or different magnetic parameters. We find a very good agreement between the shape of the model H$\rm \alpha \,$and the joint [S ii]-H$\rm \alpha \,$luminosity functions and those measured from SNR surveys in nearby galaxies.

Do AGN triggering mechanisms vary with radio power? – II. The importance of mergers as a function of radio power and optical luminosity

ABSTRACT Investigation of the triggering mechanisms of radio active galactic nuclei (radio AGN) is important for improving our general understanding of galaxy evolution. In the first paper in this series, detailed morphological analysis of high-excitation radio galaxies (HERGs) with intermediate radio powers suggested that the importance of triggering via galaxy mergers and interactions increases strongly with AGN radio power and weakly with optical emission-line luminosity. Here, we use an online classification interface to expand our morphological analysis to a much larger sample of 155 active galaxies (3CR radio galaxies, radio-intermediate HERGs, and Type 2 quasars) that covers a broad range in both 1.4 GHz radio power and [O iii] λ5007 emission-line luminosity. All active galaxy samples are found to exhibit excesses in their rates of morphological disturbance relative to 378 stellar-mass- and redshift-matched non-active control galaxies classified randomly and blindly alongside them. These excesses are highest for the 3CR HERGs (4.7σ) and Type 2 quasar hosts (3.9σ), supporting the idea that galaxy mergers provide the dominant triggering mechanism for these subgroups. When the full active galaxy sample is considered, there is clear evidence to suggest that the enhancement in the rate of disturbance relative to the controls increases strongly with [O iii] λ5007 emission-line luminosity but not with 1.4 GHz radio power. Evidence that the dominant AGN host types change from early-type galaxies at high radio powers to late-type galaxies at low radio powers is also found, suggesting that triggering by secular, disc-based processes holds more importance for lower-power radio AGN.

Modelling the nebular emission from primeval to present-day star-forming galaxies

We present a new model of the nebular emission from star-forming galaxies in a wide range of chemical compositions, appropriate to interpret observations of galaxies at all cosmic epochs. The model relies on the combination of state-of-the-art stellar population synthesis and photoionization codes to describe the ensemble of HII regions and the diffuse gas ionized by young stars in a galaxy. A main feature of this model is the self-consistent yet versatile treatment of element abundances and depletion onto dust grains, which allows one to relate the observed nebular emission from a galaxy to both gas-phase and dust-phase metal enrichment. We show that this model can account for the rest-frame ultraviolet and optical emission-line properties of galaxies at different redshifts and find that ultraviolet emission lines are more sensitive than optical ones to parameters such as C/O abundance ratio, hydrogen gas density, dust-to-metal mass ratio and upper cutoff of the stellar initial mass function. We also find that, for gas-phase metallicities around solar to slightly sub-solar, widely used formulae to constrain oxygen ionic fractions and the C/O ratio from ultraviolet and optical emission-line luminosities are reasonable faithful. However, the recipes break down at non-solar metallicities, making them inappropriate to study chemically young galaxies. In such cases, a fully self-consistent model of the kind presented in this paper is required to interpret the observed nebular emission.

SEARCHING FOR COOLING SIGNATURES IN STRONG LENSING GALAXY CLUSTERS: EVIDENCE AGAINST BARYONS SHAPING THE MATTER DISTRIBUTION IN CLUSTER CORES

The process by which the mass density profile of certain galaxy clusters becomes centrally concentrated enough to produce high strong lensing (SL) cross-sections is not well understood. It has been suggested that the baryonic condensation of the intra-cluster medium (ICM) due to cooling may drag dark matter to the cores and thus steepen the profile. In this work, we search for evidence of ongoing ICM cooling in the first large, well-defined sample of strong lensing selected galaxy clusters in the range 0.1 < z < 0.6. Based on known correlations between the ICM cooling rate and both optical emission line luminosity and star formation, we measure, for a sample of 89 strong lensing clusters, the fraction of clusters that have [OII]3727 emission in their brightest cluster galaxy (BCG). We find that the fraction of line-emitting BCGs is constant as a function of redshift for z > 0.2 and shows no statistically significant deviation from the total cluster population. Specific star formation rates, as traced by the strength of the 4000 angstrom break, D_4000, are also consistent with the general cluster population. Finally, we use optical imaging of the SL clusters to measure the angular separation, R_arc, between the arc and the center of mass of each lensing cluster in our sample and test for evidence of changing [OII] emission and D_4000 as a function of R_arc, a proxy observable for SL cross-sections. D_4000 is constant with all values of R_arc, and the [OII] emission fractions show no dependence on R_arc for R_arc > 10" and only very marginal evidence of increased weak [OII] emission for systems with R_arc < 10". These results argue against the ability of baryonic cooling associated with cool core activity in the cores of galaxy clusters to strongly modify the underlying dark matter potential, leading to an increase in strong lensing cross-sections.

THE RISE AND FALL OF THE STAR FORMATION HISTORIES OF BLUE GALAXIES AT REDSHIFTS 0.2 &lt; z &lt; 1.4

Popular cosmological scenarios predict that galaxies form hierarchically from the merger of many progenitors, each with their own unique star formation history (SFH). We use a sophisticated approach to constrain the SFHs of 4517 blue (presumably star-forming) galaxies with spectroscopic redshifts in the range 0.2 < z < 1.4 from the All-Wavelength Extended Groth Strip International Survey. This consists in the Bayesian analysis of the observed galaxy spectral energy distributions with a comprehensive library of synthetic spectra assembled using realistic, hierarchical star formation, and chemical enrichment histories from cosmological simulations. We constrain the SFH of each galaxy in our sample by comparing the observed fluxes in the B, R, I, and Ks bands and rest-frame optical emission-line luminosities with those of one million model spectral energy distributions. We explore the dependence of the resulting SFHs on galaxy stellar mass and redshift. We find that the average SFHs of high-mass galaxies rise and fall in a roughly symmetric bell-shaped manner, while those of low-mass galaxies rise progressively in time, consistent with the typically stronger activity of star formation in low-mass compared to high-mass galaxies. For galaxies of all masses, the star formation activity rises more rapidly at high than at low redshift. These findings imply that the standard approximation of exponentially declining SFHs widely used to interpret observed galaxy spectral energy distributions may not be appropriate to constrain the physical parameters of star-forming galaxies at intermediate redshifts.

On the X-ray, optical emission line and black hole mass properties of local Seyfert galaxies

We investigate the relation between X-ray nuclear emission, optical emission line luminosities and black hole masses for a sample of 47 Seyfert galaxies. The sample, which has been selected from the Palomar optical spectroscopic survey of nearby galaxies (Ho et al. 1997a, ApJS, 112, 315), covers a wide range of nuclear powers, from L2 10keV # 10 43 erg/s down to very low luminosities (L2 10keV # 10 38 erg/s). Best available data from Chandra, XMM-Newton and, in a few cases, ASCA observations have been considered. Thanks to the good spatial resolution available from these observations and a proper modeling of the various spectral components, it has been possible to obtain accurate nuclear X-ray luminosities not contaminated by o! -nuclear sources and/or di! use emission. X-ray luminosities have then been corrected taking into account the likely candidate Compton thick sources, which are a high fraction (>30%) among type 2 Seyferts in our sample. The main result of this study is that we confirm strong linear correlations between 2-10 keV, (OIII)! 5007, H luminosities which show the same slope as quasars and luminous Seyfert galaxies, independent of the level of nuclear activity displayed. Moreover, despite the wide range of Eddington ratios (L/LEdd) tested here (six orders of magnitude, from 0.1 down to # 10 7 ), no correlation is found between the X-ray or optical emission line luminosities and the black hole mass. Our results suggest that Seyfert nuclei in our sample are consistent with being a scaled-down version of more luminous AGN.

The Relationship of Hard X‐Ray and Optical Line Emission in Low‐Redshift Active Galactic Nuclei

In this paper we assess the relationship of the population of active galactic nuclei (AGNs) selected by hard X-rays to the traditional population of AGNs with strong optical emission lines. First, we study the emission-line properties of a new hard-X-ray-selected sample of 47 local AGNs (classified optically as Type 1 and 2 AGNs). We find that the hard X-ray (3-20 keV) and [O III] λ5007 optical emission-line luminosities are well-correlated over a range of about 4 orders of magnitude in luminosity (mean luminosity ratio 2.15 dex with a standard deviation of σ = 0.51 dex). Second, we study the hard X-ray properties of a sample of 55 local AGNs selected from the literature on the basis of the flux in the [O III] line. The correlation between the hard X-ray (2-10 keV) and [O III] luminosity for the Type 1 AGNs is consistent with what is seen in the hard-X-ray-selected sample. However, the Type 2 AGNs have a much larger range in the luminosity ratio, and many are very weak in hard X-rays (as expected for heavily absorbed AGNs). We then compare the hard X-ray (3-20 keV) and [O III] luminosity functions of AGNs in the local universe. These have similar faint-end slopes, with a luminosity ratio of 1.60 dex (0.55 dex smaller than the mean value for individual hard-X-ray-selected AGNs). We conclude that at low redshift, selection by narrow optical emission lines will recover most AGNs selected by hard X-rays (with the exception of BL Lac objects). However, selection by hard X-rays misses a significant fraction of the local AGN population with strong emission lines.

Black hole mass estimation using a relation between the BLR size and emission line luminosity of AGN

An empirical relation between the broad line region (BLR) size and optical continuum luminosity is often adopted to estimate the BLR size and then the black hole mass of AGNs. However, optical luminosity may not be a good indicator of photoionizing luminosity for extremely radio-loud AGNs because the jets usually contribute significantly to the optical continuum. Therefore, the black hole masses derived for blazar-type AGNs with this method are probably overestimated. Here we first derived a tight empirical relation between the BLR size and the Hp emission line luminosity, R(light - days) = 24.05(L Hβ /10 42 ergs s -1 ) 0.68 , from a sample of 34 AGNs with the BLR size estimated with the reverberation mapping technique. Then we applied this relation to estimate the black hole masses of some AGNs and found that for many extremely radio-loud AGNs the black hole masses obtained with the R - L Hβ relation are systematically lower than those derived previously with the R - L 5100 A relation, while for radio-quiet and slightly radio-loud AGNs the results obtained with these two methods are almost the same. The difference of black hole masses estimated with these two relations increases with the radio-loudness for extremely radio-loud AGNs, which is consistent with the fact that their equivalent widths of the H β emission line become smaller at greater radio-loudness. If the small Hp equivalent widths of extremely radio-loud AGNs are indeed caused by the beaming effect, we argue that the optical emission line luminosity may be a better tracer of ionizing luminosity for blazar-type AGNs and the black hole masses derived with the R - L Hβ relation are probably more accurate.

Radio sources in low-luminosity active galactic nuclei

This paper presents the results of a high resolution radio imaging survey of all known (96) low-luminosity active galactic nuclei (LLAGNs) at Mpc. We first report new 2 cm (150 mas resolution using the VLA) and 6 cm (2 mas resolution using the VLBA) radio observations of the previously unobserved nuclei in our samples and then present results on the complete survey. We find that almost half of all LINERs and low-luminosity Seyferts have flat-spectrum radio cores when observed at 150 mas resolution. Higher (2 mas) resolution observations of a flux-limited subsample have provided a 100% (16 of 16) detection rate of pc-scale radio cores, with implied brightness temperatures K. The five LLAGNs with the highest core radio fluxes also have pc-scale “jets”. Compact radio cores are almost exclusively found in massive ellipticals and in type 1 nuclei (i.e. nuclei with broad Hα emission). Only a few “transition” nuclei have compact radio cores; those detected in the radio have optical emission-line diagnostic ratios close to those of LINERs/Seyferts. This indicates that some transition nuclei are truly composite Seyfert/LINER+ region nuclei, with the radio core power depending on the strength of the former component. The core radio power is correlated with the nuclear optical “broad” Hα luminosity, the nuclear optical “narrow” emission-line luminosity and width, and with the galaxy luminosity. In these correlations LLAGNs fall close to the low-luminosity extrapolations of more powerful AGNs. The scalings suggest that many of the radio-non-detected LLAGNs are simply lower power versions of the radio-detected LLAGNs. The ratio of core radio power to nuclear optical emission-line luminosity increases with increasing bulge luminosity for all LLAGNs. Also, there is evidence that the luminosity of the disk component of the galaxy is correlated with the nuclear emission-line luminosity (but not the core radio power). About half of all LLAGNs with multiple epoch data show significant inter-year radio variability. Investigation of a sample of ~150 nearby bright galaxies, most of them LLAGNs, shows that the nuclear (≤150 mas size) radio power is strongly correlated with both the black hole mass and the galaxy bulge luminosity; linear regression fits to all ~150 galaxies give: (±0.16) log MMDO + 8.77 and (±0.21(bulge. Low accretion rates (≤ of the Eddington rate) are implied in both advection- and jet-type models. In brief, all evidence points towards the presence of accreting massive black holes in a large fraction, perhaps all, of LLAGNs, with the nuclear radio emission originating in either the accretion inflow onto the massive black hole or from jets launched by this black hole–accretion disk system.

Radio galaxies with a 'double-double' morphology--III. The case of B 1834+620

We present a study of the peculiar radio galaxy B 1834+620. It is characterized by the presence of a 420-kpc large edge-brightened radio source which is situated within, and well aligned with, a larger (1.66 Mpc) radio source. Both sources apparently originate in the same host galaxy, which has an R-s magnitude of 19.7 and a redshift of 0.5194, as determined from the strong emission lines in the spectrum. We have determined the rotation measures towards this source, as well as the radio spectral energy distribution of its components. The radio spectrum of the large outer source is steeper than that of the smaller inner source. The radio core has a spectrum that peaks at a frequency of a few GHz. The rotation measures towards the four main components are quite similar, within similar to 2 rad m(-2) of 58 rad m(-2). They are probably largely Galactic in origin. We use the presence of a bright hotspot in the northern outer lobe to constrain the advance velocity of the inner radio lobes to the range between 0.19c and 0.29c, depending on the orientation of the source. This corresponds to an age of this structure in the range between 2.6 and 5.8 Myr. We estimate a density of the ambient medium of the inner lobes of less than or similar to 1.6 x 10(-30) g cm(-3) (particle density less than or similar to 8 x 10(-7) cm(-3)). A low ambient density is further supported by the discrepancy between the large optical emission-line luminosity of the host galaxy and the relatively low radio power of the inner lobes.

ASCA Observations of the Gigahertz-peaked Spectrum Radio Galaxies 1345+125 and 2352+495

We present ASCA SIS and GIS observations of two GHz peaked spectrum (GPS) radio galaxies, PKS 1345+125 (4C12.50, z = 0.122) and 2352+495 (z = 0.237). In the energy band 2–10 keV, 1345+125 is detected with about 2 × 1043 ergs s-1, while 2352+495 is not detected with an upper limit < 7 × 1042 ergs s-1. This is the first reported detection of X-ray emission from a GPS radio galaxy. These measurements do not violate predictions of Heinz et al.'s recent evolving source model for radio sources, although deeper X-ray observations are needed for a strong test of the model. The host galaxy of 1345+125 contains two nuclei separated by 2'' (4 kpc) which are not resolved by the ASCA observations. We suggest that the X-rays are emitted by the western of the two nuclei, which Gilmore & Shaw have shown has a NLRG/Seyfert-2 optical spectrum and which Evans et al. have recently identified with the GPS radio source. We obtain model dependent estimates for the 1345+125 radio source age of about 3 × 104 yr and expansion velocity of approximately 0.02c. We show that in samples of Seyfert 1's and powerful extended radio galaxies, optical emission-line luminosities are of a strength consistent with photoionization by the embedded active galactic nucleus (AGN; estimated using ASCA observations), and 1345+125 fits this picture assuming the X-ray emission is from the western nucleus. In contrast, the extrapolated limits on the nuclear ionizing continuum in 2352+495 are too low to account for the luminosity of the narrow emission-line region. If this is confirmed by further observations, it would favor a model in which some fraction of the emission lines are powered by shocks induced by the radio source or in which some of the AGN photons that ionize the gas are obscured from our view.

H(alpha) Imaging of the Hickson Compact Group 62

We report results of a search for optical emission line gas in the Hickson compact group 62. From narrow band (H-alpha) imaging observations we estimate 10^4 Msun of ionized hydrogen gas within the central regions of three of the galaxies in the group. There has been considerable interest in this group since ROSAT detected an extended halo of diffuse X-ray emission, possibly with a cooling flow at the center. The optical emission line luminosities from the three galaxies are comparable to each other (~10^{39} ergs/s) and resemble those seen in normal X-ray luminous early type galaxies. There is no evidence for any excess emission in the galaxy which lies at the center of the X-ray cooling flow. We find that the most likely source of excitation for the emission line nebulosities is photoionization by young stars.

Optical–Radio Connections AGN Illumination or Jet/cloud Interactions?

Many of the most important discoveries in the study of extragalactic radio sources have resulted from investigations of the relationships between optical and radio properties. The optical/radio connections include: correlations between optical emission line luminosity and radio power; alignments between optical/UV and radio structures; and UV excesses in the spectral energy distributions of radio galaxies compared with normal early-type galaxies.

No X-Ray--luminous Starbursts in the Einstein Medium Sensitivity Survey, Either

view Abstract Citations (16) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS No X-Ray--luminous Starbursts in the Einstein Medium Sensitivity Survey, Either Halpern, Jules P. ; Helfand, David J. ; Moran, Edward C. Abstract We continue to investigate recurrent claims that a substantial number of "normal" star-forming galaxies may have X-ray luminosities in the range 1042-44 ergs s-1. In this installment, we present new spectra of four such emission-line galaxies that were ambiguously classified in the Einstein Extended Medium Sensitivity Survey (EM SS), and find that they all have intermediate-type Seyfert nuclei as evidenced by broad components of their Hα lines. We argue that any of the remaining emission-line galaxies in the EMSS with 1042 < Lχ < 1044 ergs s-1 that were flagged as needing further spectroscopic work are almost certain to have active nuclei as well. We conclude that in these as well as other samples of X-ray-selected emission-line galaxies, X-ray luminosities in excess of 1042 ergs s 1 can and should be attributed to an active nucleus, even in the case that most of the infrared continuum or optical emission-line luminosity is caused by star formation. There is as yet no good evidence for X-ray-luminous starbursts. Publication: The Astrophysical Journal Pub Date: November 1995 DOI: 10.1086/176424 Bibcode: 1995ApJ...453..611H Keywords: GALAXIES: SEYFERT; GALAXIES: STARBURST; X-RAYS: GALAXIES; GALAXIES: ACTIVE full text sources ADS | data products SIMBAD (11) NED (4)

The late-time bolometric luminosity of SN 1987A

We present infrared photometry of SN 1987A in the J, H, K, L, M, 10, and 20 micron filters through day 1352 since the explosion of the Supernova. We find that both the optical and mid-infrared magnitudes are slowly leveling out through day 1352 after their rapid decline in brightness during the epoch of dust formation. The near infrared colors (V-J, V-H, and V- K&gt; initially reddened after dust formation around day 500, but by days 900-1000, they began to evolve to the blue, perhaps due to the thinning of the dust. Optical spectra obtained through day 1150 show no evidence for a sudden drop in the optical emission-line luminosities. This suggests that the region of optical emission has not undergone the so- called "infrared catastrophe," when the cooling of the ejecta becomes dominated by the infrared fine-structure lines, at least in the case described by the simple models of Fransson &amp; Chevalier [ApJL, 322, L15 (1987)]. More complicated models where the higher density regions are cooled by the fine-structure lines at the same time that the nebular dust is thinning could be qualitatively consistent with the data. The infrared data have been combined with optical photoelectric and CCD UBVRI photometry obtained at CTIO to study the temporal evolution of the bolometric luminosity of SN 1987A. By day 1000, another source of energy beside the radioactive decay of ^56^Co is needed to explain the slow leveling off to the bolometric luminosity decline. We can formally fit our data with the following energy sources: 5+/-1 times the predicted ("solar") amount of ^57^Co/^56^Co;10+/-3 times the predicted amount of ^44^Ti; or a constant energy input of 37.3+/-0.15 dex (log_10_(ergs s^- 1^)]. The energy input is unspecified; it could be a pulsar, light echo, or other unidentified energy source. Only the enhanced ^57^Co/^56^Co provides a good fit at all times to the data. The enhanced ^57^Co, however, is in conflict with published hard x-ray and infrared spectral data. A careful reanalysis of the uncertainties in the observed hard x-ray and ultraviolet-optical-infrared fluxes, and the model predictions, suggests that all the data can be fit by the energy deposition from 0.075M_sun_ of ^56^Ni, a ^57^Co/^56^Co between 2.5 and 4 times "solar," and "solar" ^44^Ti.

The radio properties of cD galaxies in Abell clusters. I - an X-ray selected sample

The radio and X-ray properties of a sample of 27 cD galaxies in rich clusters are presented. The radio data consist of 6 cm VLA maps at a resolution of 1-2 arcsec. The X-ray data consist of images and surface-brightness profiles from the Einstein IPC and derived quantities such as cooling times, mass-accretion rates, and thermal pressures from Arnaud (1988). These data are used to explore the relationship between X-ray cooling cores, and the power and morphology of the radio emission. It is found that 71 percent of the cD's with X-ray cooling cores are radio loud, whereas a smaller but still significant 23 percent of cD's without cooling cores are detected at 6 cm above 0.2 mJy. Among the radio galaxies in noncooling core clusters are luminous and extended wide-angle tails. There is a weak correlation between the mass-accretion rate and the radio power for cD's. There is also an interesting class of cooling core cluster (e.g., A2052) with small diameter, amorphous radio emission that may be the result of diffusion along radial magnetic fields set up in cooling inflows. Finally, the relationships between optical emission-line luminosity with radio power and mass-accretion rate are examined.

Low-luminosity radio sources in early-type galaxies

We have made a sensitive radio continuum survey of 114 nearby E and S0 galaxies to search for weak sources. The radio detection rate is 42 per cent, with a flux limit of 0.8 mJy at 5 GHz. By deriving the radio luminosity function for a complete sample, we show that most bright early-type galaxies have low-luminosity |$({10}^{19}-{10}^{21}\,\text{W Hz}^{-1})$| non-thermal radio sources. Galaxies of similar optical luminosity vary widely in radio luminosity, but a characteristic radio power (the 30th percentile) rises roughly as the optical luminosity squared. S0 galaxies have weaker radio sources on average than elliptical galaxies, but this can be explained by the low luminosity of most S0 bulges relative to ellipticals. We find no correlation between radio power and axial ratio for galaxies with radio luminosities below |${10}^{23}\,\text{W Hz}^{-1}.$| Most early-type galaxies have modest amounts of ionized gas in their central regions, but there is no correlation between optical emission-line luminosity and the presence or strength of radio emission at the low luminosities considered here.