Search

We present a broadband spectrophotometric analysis of an unusual quasar, SDSS J160558.86+474300.1, at z = 0.9, found in a systematic search for reddened radio-loud narrow-line Seyfert 1 galaxies (NLS1s). J1605+4743 qualifies for the conventional definition of an NLS1 in its permitted emission line widths and H β /[O iii ] flux ratio. It also shows strong Fe ii emissions. J1605+4743 has a steep radio spectrum. With a radio loudness of ∼150 (70) before (after) reddening correction, it is among the most radio-loud NLS1s discovered. In addition, the blueshifted emission lines are also found to be weak, suggesting that it can be an exotic "wind-dominated" Seyfert similar to weak-line quasars, especially the ones with strong reddening. As an extreme hybrid central engine, its environment and host galaxy become rather intriguing. We discover in it a proximate 2175 Å absorber with a bump strength similar to the average value of 2175 Å absorbers in the Milky Way, which we suspect can be intrinsic to the quasar. In addition, the quasar seems to have enhanced instead of suppressed star formation at a rate of ≳94 M ⊙ yr−1. The combination of these unusual properties, i.e., the unique extinction, strong Fe ii and [O ii ] lines, weak [O iii ], Mg ii, and Balmer lines, and large radio loudness, might hold important clues to accretion physics, the formation/destruction of dust grains in the environment of active galactic nuclei, and possibly also the coevolution of supermassive black holes and their host galaxies in general. [ABSTRACT FROM AUTHOR]

Gas accretion is an important process in the evolution of galaxies, but it has limited direct observational evidences. In this paper, we report the detection of a possible ongoing gas accretion event in a blue compact dwarf (BCD) galaxy, MaNGA 8313-1901, observed by the Mapping Nearby Galaxies and Apache Point Observatory (MaNGA) program. This galaxy has a distinct off-centered blue clump to the northeast (the NE clump) that shows low metallicity and enhanced star formation. The kinematics of the gas in the NE clump also seems to be detached from the host BCD galaxy. Together with the metallicity drop of the NE clump, it suggests that the NE clump likely has an external origin, such as gas accretion or galaxy interaction, rather than an internal origin, such as an H II complex in the disk. After removing the underlying host component, we find that the spectrum of the “pure” clump can match very well with a modeled spectrum containing a stellar population of the young stars (≤7 Myr) only. This may imply that the galaxy is experiencing an accretion of cold gas, instead of a merger event involving galaxies with significant preexisting old stars. We also find signs of another clump (the SW clump) at the southwest corner of the host galaxy, and the two clumps may share the same origin of gas accretion. [ABSTRACT FROM AUTHOR]

The role of H i content in galaxy interactions is still under debate. To study the H i content of galaxy pairs at different merging stages, we compile a sample of 66 major-merger galaxy pairs and 433 control galaxies from the Sloan Digital Sky Survey IV (SDSS-IV) MaNGA IFU survey. In this study, we adopt kinematic asymmetry as a new effective indicator to describe the merging stage of galaxy pairs. With archival data from the HI-MaNGA survey and new observations from the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we investigate the differences in H i gas fraction (f H I), star formation rate (SFR), and H i star formation efficiency (SFEH I) between the pair and control samples. Our results suggest that the H i gas fraction of major-merger pairs on average is marginally decreased by ∼15% relative to isolated galaxies, implying mild H i depletion during galaxy interactions. Compared to isolated galaxies, pre-passage paired galaxies have similar f H I, SFR, and SFEH I, while pairs during the pericentric passage have weakly decreased f H I (âˆ'0.10 ± 0.05 dex), significantly enhanced SFR (0.42 ± 0.11 dex), and SFEH I (0.48 ± 0.12 dex). When approaching the apocenter, paired galaxies show marginally decreased f H I (âˆ'0.05 ± 0.04 dex), comparable SFR (0.04 ± 0.06 dex), and SFEH I (0.08 ± 0.08 dex). We propose that the marginally detected H i depletion may originate from the gas consumption in fueling the enhanced H2 reservoir of galaxy pairs. In addition, new FAST observations also reveal a H i absorber (N H I ∼ 4.7 Ă— 1021 cmâˆ'2), which may suggest gas infalling and the triggering of active galactic nuclei activity. [ABSTRACT FROM AUTHOR]

We present a detailed analysis of the broad absorption line system in the quasar SDSS J122017.06+454941.1, which are clearly detected in hydrogen Lyman series and metal lines, such as C iv , Si iv , Si iii , Al iii , and C ii , with a similar velocity as that of the broad emission lines. We reliably measured the column densities of H i , Al iii , and C ii , and obtained a low limit to Si iv and Si iii. With the help of the photoionization simulations, we found that the absorption gas has a hydrogen number density nH ≈ 1011.03 cm−3 and a hydrogen column density NH ≈ 1021.0 cm−2, and is exposed to the radiation with an ionization parameter U ≈ 10−1.25, and thus located the absorber at ∼0.3 pc from the central supermassive black hole, remarkably similar to the radius of the broad-line region (BLR; 0.17–0.84 pc as estimated by the luminosity–radius relation) of the quasar. It is likely that our line of sight may happen to intercept the low-column part of the BLR with a high density similar to that of the inferred value of the absorber. We suggest that detection of Al iii absorption line doublet in moderate quality quasar spectra could be a good indicator of dense gases, provided that the neutral hydrogen column density of the absorber is. [ABSTRACT FROM AUTHOR]

We present detailed studies of the partially obscured quasar 2MASS J151653.23+190048.2 with continuous broadband spectrophotometry from near-infrared (NIR) through optical to ultraviolet (UV). The NIR and optical spectra show strong broad emission lines, while the UV spectrum is dominated by a set of rich intermediate-width emission lines (IELs). These IELs, unshifted with respect to the quasar systemic velocity measured by narrow emission lines, share a common profile of about 1900 in FWHM, in contrast to the Balmer and Paschen broad emission lines of FWHM ∼6300 observed in the optical and NIR. The intermediate width of these lines indicates that the emitting gas may come from the dusty torus region. However, the observed peculiar IEL intensity ratios, such as N v λ1240/Lyα, indicate that the emitting gas has a very high density, up to. Such a high density is unusual for gas around the dusty torus region, except that we consider mechanisms such as shocks that can produce local ultradense gas. We speculate that these emission lines could originate from the shock region, possibly induced by the quasar outflow colliding with the inner wall of the dusty torus. If true, this may give us an opportunity to peep at the quasar outflows at the scale of the dusty torus that have so far been elusive due to the limited resolving powers of existing facilities. [ABSTRACT FROM AUTHOR]

Using deep narrowband H2S1 and Ks-band imaging data obtained with CFHT/WIRCam, we identify a sample of 56 Hα emission-line galaxies (ELGs) at z = 2.24 with the 5σ depths of H2S1 = 22.8 and Ks = 24.8 (AB) over a 383 arcmin2 area in the Extended Chandra Deep Field South. A detailed analysis is carried out with existing multi-wavelength data in this field. Three of the 56 Hα ELGs are detected in Chandra 4 Ms X-ray observations and two of them are classified as active galactic nuclei. The rest-frame UV and optical morphologies revealed by HST/ACS and WFC3 deep images show that nearly half of the Hα ELGs are either merging systems or have a close companion, indicating that the merging/interacting processes play a key role in regulating star formation at cosmic epoch z = 2-3. About 14% are too faint to be resolved in the rest-frame UV morphology due to high dust extinction. We estimate dust extinction from spectral energy distributions. We find that dust extinction is generally correlated with Hα luminosity and stellar mass. Our results suggest that Hα ELGs are representative of star-forming galaxies. Applying extinction corrections to individual objects, we examine the intrinsic Hα luminosity function (LF) at z = 2.24, obtaining a best-fit Schechter function characterized by a faint-end slope of α = – 1.3. This is shallower than the typical slope of α ≃ –1.6 in previous works based on constant extinction correction. We demonstrate that this difference is mainly due to the different extinction corrections. The proper extinction correction is thus the key to recovering the intrinsic LF as the extinction globally increases with Hα luminosity. Moreover, we find that our Hα LF mirrors the stellar mass function of star-forming galaxies at the same cosmic epoch. This finding indeed reflects the tight correlation between star formation rate and stellar mass for star-forming galaxies, i.e., the so-called main sequence. [ABSTRACT FROM AUTHOR]

Galaxy-galaxy mergers and close interactions have long been regarded as a viable mechanism for channeling gas toward the central supermassive black holes (SMBHs) of galaxies which are triggered as active galactic nuclei (AGNs). AGN pairs, in which the central SMBHs of a galaxy merger are both active, are expected to be common from such events. We conduct a systematic study of 1286 AGN pairs at z ~ 0.1 with line-of-sight velocity offsets Δv < 600 km s-1 and projected separations Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed, selected from the Seventh Data Release of the Sloan Digital Sky Survey (SDSS). This AGN pair sample was drawn from 138,070 AGNs optically identified based on diagnostic emission line ratios and/or line widths. The fraction of AGN pairs with Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed among all spectroscopically selected AGNs at 0.02 < z < 0.16 is 3.6% after correcting for SDSS spectroscopic incompleteness; ~30% of these pairs show morphological tidal features in their SDSS images, and the fraction becomes ≳80% for pairs with the brightest nuclei. Our sample increases the number of known AGN pairs on these scales by more than an order of magnitude. We study their AGN and host-galaxy star formation properties in a companion paper. [ABSTRACT FROM AUTHOR]

We study theoretically the interfacial electronic property of a heterojunction made from two Mott insulators (MI) with different magnetic structures. By means of unrestricted Hartree-Fock calculations in real space, we find that a charge dipole can form spontaneously near the interface of the MI/MI heterojunction. The magnitude of this charge dipole depends strongly on the magnetic states of both sides of the heterojunction. Combining with the result from an exactly solvable two-site toy model, we argue that the interface dipole arises from exchange effects as well as its asymmetry intrinsic to the heterojunction near the interface. Our study may shed light on the fabrication of ultrathin ferroelectric and magnetoelectric devices. [ABSTRACT FROM AUTHOR]

The Sloan Digital Sky Survey (SDSS) has validated and made publicly available its First Data Release. This consists of 2099 deg2 of five-band (u, g, r, i, z) imaging data, 186,240 spectra of galaxies, quasars, stars and calibrating blank sky patches selected over 1360 deg2 of this area, and tables of measured parameters from these data. The imaging data go to a depth of r ≈ 22.6 and are photometrically and astrometrically calibrated to 2% rms and 100 mas rms per coordinate, respectively. The spectra cover the range 3800–9200 Å, with a resolution of 1800–2100. This paper describes the characteristics of the data with emphasis on improvements since the release of commissioning data (the SDSS Early Data Release) and serves as a pointer to extensive published and on-line documentation of the survey., Astronomy

We investigate the resolved relation between local extinction and star formation surface density within nearby star-forming galaxies selected from the MaNGA survey. Balmer decrement measurements imply an extinction of the Hα line emission that scales approximately linearly with the logarithm of the star formation surface density: . Secondary dependencies are observed such that, at a given ΣSFR, regions of lower metallicity and/or enhanced Hα equivalent width (EW) suffer less obscuration than regions of higher metallicity and/or lower Hα EW. Spaxels lying above the mean relation also tend to belong to galaxies that are more massive, larger, and viewed under higher inclination than average. We present a simple model in which the observed trends can be accounted for by a metallicity-dependent scaling between ΣSFR and Σdust via a superlinear Kennicutt–Schmidt relation (nKS ∼ 1.47) and a dust-to-gas ratio that scales linearly with metallicity (DGR(Z⊙) = 0.01). The relation between the resulting total dust column and observed effective extinction toward nebular regions requires a geometry for the relative distribution of Hα-emitting regions and dust that deviates from a uniform foreground screen and also from an entirely homogeneous mixture of dust and emitting sources. The best-fit model features an Hα EW and galactocentric-distance-dependent fraction of the dust mass in a clumpy foreground screen in front of a homogeneous mixture. [ABSTRACT FROM AUTHOR]

In this study, we investigated the degradation mechanisms of the luminance performance of organic light-emitting diodes (OLEDs) when their top electrode films were deposited by sputter deposition process. During the sputter deposition of the top electrode films, the suppression of the incidence of high-energy electrons on the substrate was attempted using various methods. As a result, we found that during electrode deposition, the incidence of the high-energy secondary electrons, which were emitted from the target surface, on the substrate was the main cause of the significant degradation of the luminance performance. It was also found that the application of a magnetic field by setting permanent magnets near the substrate holder and the insertion of a shield plate near the target cathode were effective in suppressing the incidence of secondary electrons on the substrate. [ABSTRACT FROM AUTHOR]