We report the discovery of two low-luminosity quasars at z similar to 4, both of which show prominent N IV lambda 1486 emission. This line is extremely rare in quasar spectra at any redshift; ...detecting it in two of a sample of 23 objects (i.e., similar to 9% of the sample) is intriguing and is likely due to the low-luminosity, high-redshift quasar sample we are studying. This is still a poorly explored regime, where contributions from associated, early starbursts may be significant. One Interpretation of this line posits photoionization by very massive young stars. Seeing N IV lambda 1486 emission in a high-redshift quasar may thus be understood in the context of coformation and early coevolution of galaxies and their supermassive black holes. Alternatively, we may be seeing a phenomenon related to the early evolution of quasar broad emission line regions. The nondetection (and possibly even broad absorption) of N v lambda 1240 line in the spectrum of one of these quasars may support that interpretation. These two objects may signal a new faint quasar population or an early AGN evolutionary stage at high redshifts.
We present results of a deep spectroscopic survey designed to quantify the
statistics of the escape of ionizing photons from star-forming galaxies at z~3.
We measure the ratio of ionizing to ...non-ionizing UV flux density
<f900/f1500>_obs, where f900 is the mean flux density evaluated over the range
880,910 A. We quantify the emergent ratio of ionizing to non-ionizing UV flux
density by analyzing high-S/N composite spectra formed from sub-samples with
common observed properties and numbers sufficient to reduce the statistical
uncertainty in the modeled IGM+CGM correction to obtain precise values of
<f900/f1500>_out, including a full-sample average
<f900/f1500>_out=$0.057\pm0.006$. We further show that <f900/f1500>_out
increases monotonically with Ly$\alpha$ rest equivalent width, inducing an
inverse correlation with UV luminosity as a by-product. We fit the composite
spectra using stellar spectral synthesis together with models of the ISM in
which a fraction f_c of the stellar continuum is covered by gas with column
density N(HI). We show that the composite spectra simultaneously constrain the
intrinsic properties of the stars (L900/L1500)_int along with f_c, N(HI),
E(B-V), and $f_{esc,abs}$, the absolute escape fraction of ionizing photons. We
find a sample-averaged $f_{esc,abs} =0.09\pm0.01$, and that subsamples fall
along a linear relation $\langle f_{esc,abs}\rangle \sim 0.75W(Ly\alpha)/110
A$. We use the FUV luminosity function, the distribution function
$nW(Ly\alpha)$, and the relationship between $W(Ly\alpha)$ and
<f900/f1500>_out to estimate the total ionizing emissivity of $z\sim3$
star-forming galaxies with Muv < -19.5: $\epsilon_{LyC}\sim 6\times10^{24}$
ergs/s/Hz/Mpc$^3$, exceeding the contribution of QSOs by a factor of $\sim 3$,
and accounting for $\sim50$% of the total $\epsilon_{LyC}$ at $z\sim3$
estimated using indirect methods.
We present results of a deep spectroscopic survey designed to quantify the statistics of the escape of ionizing photons from star-forming galaxies at z~3. We measure the ratio of ionizing to ...non-ionizing UV flux density <f900/f1500>_obs, where f900 is the mean flux density evaluated over the range 880,910 A. We quantify the emergent ratio of ionizing to non-ionizing UV flux density by analyzing high-S/N composite spectra formed from sub-samples with common observed properties and numbers sufficient to reduce the statistical uncertainty in the modeled IGM+CGM correction to obtain precise values of <f900/f1500>_out, including a full-sample average <f900/f1500>_out=\(0.057\pm0.006\). We further show that <f900/f1500>_out increases monotonically with Ly\(\alpha\) rest equivalent width, inducing an inverse correlation with UV luminosity as a by-product. We fit the composite spectra using stellar spectral synthesis together with models of the ISM in which a fraction f_c of the stellar continuum is covered by gas with column density N(HI). We show that the composite spectra simultaneously constrain the intrinsic properties of the stars (L900/L1500)_int along with f_c, N(HI), E(B-V), and \(f_{esc,abs}\), the absolute escape fraction of ionizing photons. We find a sample-averaged \(f_{esc,abs} =0.09\pm0.01\), and that subsamples fall along a linear relation \(\langle f_{esc,abs}\rangle \sim 0.75W(Ly\alpha)/110 A\). We use the FUV luminosity function, the distribution function \(nW(Ly\alpha)\), and the relationship between \(W(Ly\alpha)\) and <f900/f1500>_out to estimate the total ionizing emissivity of \(z\sim3\) star-forming galaxies with Muv < -19.5: \(\epsilon_{LyC}\sim 6\times10^{24}\) ergs/s/Hz/Mpc\(^3\), exceeding the contribution of QSOs by a factor of \(\sim 3\), and accounting for \(\sim50\)% of the total \(\epsilon_{LyC}\) at \(z\sim3\) estimated using indirect methods.
We report on observations of the nova-like cataclysmic variable AE Aqr
performed by MAGIC. The observations were part of a quasi-simultaneous
multi-wavelength campaign carried out between 2012 May ...and June covering the
optical, UV, X-ray and gamma-ray ranges. MAGIC conducted the campaign and
observed the source during 12 hours. The other instruments involved were KVA,
Skinakas, and Vidojevica in the optic and Swift in the X-ray. We also used
optical data from the AAVSO. The goals were to: monitor the variability of the
source at different wavelengths, perform gamma-ray studies coincident with the
highest states of the source at the other wavelengths, and confirm or rule out
previous claims of detection of very-high-energy emission from this object. We
report on a search for steady TeV emission during the whole observation, for
variable TeV emission coincident with the highest optical and X-ray states and
periodic TeV emission at the 33.08 s rotation period (30.23 mHz rotation
frequency) of the white dwarf and its first harmonic (60.46 mHz rotation
frequency). These are the first observations under good weather conditions
performed by the present generation of IACTs for this object.
New Astron.Rev.50:140-145,2006 Observations of QSOs at z ~ 5.7 - 6.4 show the appearance of Gunn-Peterson
troughs around z ~ 6, and a change in the slope of the IGM optical depth tau(z)
near z ~ 5.5. ...These results are interpreted as a signature of the end of the
reionization era, which probably started at considerably higher redshifts.
However, there also appears to be a substantial cosmic variance in the
transmission of the IGM, both along some lines of sight, and among different
lines of sight, in this intriguing redshift regime. We suggest that this is
indicative of a spatially uneven reionization, possibly caused by the
bias-driven primordial clustering of the reionization sources. There is also
some independent evidence for a strong clustering of QSOs at z ~ 4 - 5 and
galaxies around them, supporting the idea of the strong biasing of the first
luminous sources at these redshifts. Larger samples of high-z QSOs are needed
in order to provide improved, statistically significant constraints for the
models of these phenomena. We expect that the Palomar-Quest (PQ) survey will
soon provide a new set of QSOs to be used as cosmological probes in this
redshift regime.
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