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SDSS J083942.11+380526.3 (⁠|$z=2.315$|⁠) is an iron low-ionization broad absorption lines quasar that exhibits visible Balmer absorption lines (H  |$\alpha$|⁠), implying a significant |$n=2$| population. The quasar also shows an array of absorption lines, including O  i , Ni  ii , Fe  ii , Mg  ii , Al  iii  to C  iv , and N v. The high-ionization absorption lines such as C  iv and Si  iv are revealed by slightly blueshifted broad absorption lines troughs. The resonance doublets such as Mg  ii and Al  iii are saturated but did not reached zero intensity which indicates that the broad-line region (BLR) is partially covered. Overall, however, the absorption is predominantly from low-ionization Fe  ii lines, emitted from ground and excited states up to at least 3.814 eV. This implies that the absorbing gas spans the hydrogen ionization front and extends into the partially ionized zone where neutral hydrogen is certainly present. Notably, the hydrogen line spectrum of the quasar shows no signature of expected Ly  |$\alpha$| absorption. Instead, the line spectrum shows an unusual Ly  |$\alpha$| emission characterized by a fully filled emission line spectrum which is a composite of a strong narrow core superposed on a weak broad base. Taking into account the effect of partial covering to BLR, we have extracted a strong Damped Ly α systems (DLA) trough in Ly  |$\alpha$| emission region. To fit the spectrum, we performed photoionized model calculations and compared them to the observations. We found that photoionization modelling using cloudy can successfully reproduce the main characteristics of the quasar spectrum, and the predicted neutral hydrogen column density arising from the clouds responsible for the low-ionization absorption provides a good match to the extracted DLA trough. This indicates that both the DLA and the low-ionization absorption arise from the same medium that is roughly collocated with the dusty torus. [ABSTRACT FROM AUTHOR]

[O  iii ] λλ4960,5008 doublet are often the strongest narrow emission lines in starburst galaxies and quasi-stellar objects (QSOs), and thus are a promising probe to possible variation of the fine-structure constant α over cosmic time. Previous such studies using QSOs optical spectra were limited to z < 1. In this work, we constructed a sample of 40 spectra of Ly α emitting galaxies (LAEs) and a sample of 46 spectra of QSOs at 1.09 < z < 3.73 using the VLT/X-Shooter near-infrared spectra publicly available. We measured the wavelength ratios of the two components of the spin-orbit doublet and accordingly calculated α(z) using two methods. Analysis on all of the 86 spectra yielded Δα/α = (− 3 ± 6) × 10−5 with respect to the laboratory α measurements, consistent with no variation over the explored time interval. If assuming a uniform variation rate, we obtained α−1dα/d t = (− 3 ± 6) × 10−15 yr−1 within the last 12 Gyr. Extensive tests indicate that α variation could be better constrained using starburst galaxies' spectra than using QSO spectra in future studies. [ABSTRACT FROM AUTHOR]

This paper reports the detection of a strong Wolf–Rayet (W-R) emission bump feature at 4400–4700 Å in the optical spectrum of a distant galaxy SDSS J150009.81+452844.4 at a redshift of 0.453. The estimated number of W-R stars is 1.5 × 105 without applying any internal extinction correction, and at least 4.5 × 105 after correcting for dust extinction. Such a number, though with uncertainties inherent from the extinction correction and others, appears to outnumber those in previous W-R galaxies after correcting for intrinsic dust extinction with the numbers available in the literature. These massive stars must have formed in an instantaneous star-forming episode lasting less than about 5 Myr. We estimate a star formation rate of at least ∼80 |$\mathrm{M}_{\odot }\, \mathrm{yr^{-1}}$|⁠ , indicative of a violent starburst. Its mid-infrared spectrum resembles closely those of typical local ultraluminous infrared galaxies (ULIRGs). From optical to ultraviolet, it possesses a luminous blue continuum, indicating that the starburst is not heavily obscured, in contrast to that found in most ULIRGs. There is evidence for strong outflows based on the detection of systematically blue-shifted broad wings in the nebular emission lines (a bulk velocity −190 km s−1), as well as in the blue-shifted Mg  ii absorption lines. The emission-line gases show a wide velocity range, from −1200 to ∼−2000 km s−1 in blueshift to 570 km s−1 in redshift. We interpret this as a galactic fountain, of which part of the outflowing gas may be falling back to the galactic plane. Our method could be used to find a sample of similar objects, which would help understand the star formation history and stellar feedback in starburst galaxies. [ABSTRACT FROM AUTHOR]