arXiv subjects

Tuo Ji

Publications and source records attributed to Tuo Ji.

41 records · Page 3Linked to original sources

arXiv2014

Unshifted Metastable He I* Mini-Broad Absorption Line System in the Narrow Line Type 1 Quasar SDSS J080248.18$+$551328.9

We report the identification of an unusual absorption line system in the quasar SDSS J080248.18$+$551328.9 and present a detailed study of the system, incorporating follow-up optical and NIR spectroscopy. A few tens of absorption lines are detected, including He I*, Fe II* and Ni II* that arise from metastable or excited levels, as well as resonant lines in Mg I, Mg II, Fe II, Mn II, and Ca II. All of the isolated absorption lines show the same profile of width $Δv\sim 1,500$km s$^{-1}$ centered at a common redshift as that of the quasar emission lines, such as [O II], [S II], and hydrogen Paschen and Balmer series. With narrow Balmer lines, strong optical Fe II multiplets, and weak [O III] doublets, its emission line spectrum is typical for that of a narrow-line Seyfert 1 galaxy (NLS1). We have derived reliable measurements of the gas-phase column densities of the absorbing ions/levels. Photoionization modeling indicates that the absorber has a density of $n_{\rm H} \sim (1.0-2.5)\times 10^5~ {\rm cm}^{-3}$ and a column density of $N_{\rm H} \sim (1.0-3.2)\times 10^{21} \sim {\rm cm}^{-2}$, and is located at $R\sim100-250$ pc from the central super-massive black hole. The location of the absorber, the symmetric profile of the absorption lines, and the coincidence of the absorption and emission line centroid jointly suggest that the absorption gas is originated from the host galaxy and is plausibly accelerated by stellar processes, such as stellar winds \zhy{and/or} supernova explosions. The implications for the detection of such a peculiar absorption line system in an NLS1 are discussed in the context of co-evolution between super-massive black hole growth and host galaxy build-up.

astro-ph.GA↗

arXiv2014

High resolution deep imaging of a bright radio quiet QSO at z~3

We have obtained deep J & Ks-band images centered on a bright radio quiet QSO UM402 (z_{em}=2.856) using IRCS camera and AO systems on Subaru Telescope, as well as retrieved WFC3/F140W archive images. A faint galaxy (m_{k}=23.32 +/- 0.05 in the Vega system) that lies ~ 2.4" north of the QSO sightline has been clearly resolved in all three deep high resolution datasets, and appears as an irregular galaxy with two close components in the Ks-band images (separation ~ 0.3"). Given the small impact parameter (b=19.6 kpc, at z_{lls}=2.531), as well as the red color of (J-Ks)_{vega} ~ 1.6, it might be a candidate galaxy giving rise to the Lyman Limit system absorption at z_{abs}=2.531 seen in the QSO spectrum. After carefully subtracting the PSF from the QSO images, the host galaxy of this bright radio quiet QSO at z ~ 3 was marginally revealled. We placed a low limit of the host component of m_{k} ~ 23.3 according to our analyses.

astro-ph.CO↗

arXiv2013

Anomalously Steep Reddening Law in Quasars: An Exceptional Example Observed in IRAS14026+4341

A fraction of the heavily reddened quasars require a reddening curve which is even steeper than that of the Small Magellanic Cloud. In this paper, we thoroughly characterize the anomalously steep reddening law in quasars, via an exceptional example observed in IRAS 14026+4341. By comparing the observed spectrum to the quasar composite spectrum, we derive a reddening curve in the rest-frame wavelength range of 1200 Å--10000 Å. It is featured with a steep rise at wavelengths shorter than 3000 Å, but no significant reddening at longer wavelengths. The absence of dust reddening in optical continuum is confirmed by the normal broad-line Balmer decrement (the H$α$/H$β$ ratio) in IRAS 14026+4341. The anomalous reddening curve can be satisfactorily reproduced by a dust model containing silicate grains in a power-law size distribution, $dn(a)/da \propto a^{-1.4}$, truncated at a maximum size $a_{max}=70 {\rm nm}$. The unusual size distribution may be caused by the destruction of large "stardust" grains by quasar activities or a different dust formation mechanism (i.e., the in situ formation of dust grains in quasar outflows). It is also possible that the analogies of the dust grains observed toward the Galactic center is responsible for the steep reddening curve. In addition, we find that IRAS 14026+4341 is a weak emission-line quasar (i.e., PHL 1811 analogies) with heavy dust reddening and blueshifted broad absorption lines.

astro-ph.CO↗

arXiv2012

Rapid Infrared Variability of Three Radio-loud Narrow-line Seyfert 1 Galaxies: A View from the Wide-field Infrared Survey Explorer

Using newly released data from the Wide-field Infrared Survey Explorer, we report the discovery of rapid infrared variability in three radio-loud narrow-line Seyfert 1 galaxies (NLS1s) selected from the 23 sources in the sample of Yuan et al. (2008). J0849+5108 and J0948+0022 clearly show intraday variability, while J1505+0326 has a longer measurable time scale within 180 days. Their variability amplitudes, corrected for measurement errors, are $\sim 0.1-0.2$ mag. The detection of intraday variability restricts the size of the infrared-emitting region to $\sim 10^{-3}$ pc, significantly smaller than the scale of the torus but consistent with the base of a jet. The three variable sources are exceptionally radio-loud, have the highest radio brightness temperature among the whole sample, and all show detected $γ$-ray emission in Fermi/LAT observations. Their spectral energy distributions resemble those of low-energy-peaked blazars, with a synchrotron peak around infrared wavelengths. This result strongly confirms the view that at least some radio-loud NLS1s are blazars with a relativistic jet close to our line of sight. The beamed synchrotron emission from the jet contributes significantly to and probably dominates the spectra in the infrared and even optical bands.

astro-ph.HE↗

arXiv2012

Discovery of Balmer Broad Absorption Lines in the Quasar LBQS 1206+1052

We report the discovery of Balmer broad absorption lines (BALs) in the quasar LBQS 1206+1052 and present a detailed analysis of the peculiar absorption line spectrum. Besides Mg II $λλ2796, 2803$ doublet, BALs are also detected in He I* multiplet at $λλ2946, 3189, 3889$ Åarising from metastable helium $2^3S$ level, and in H$α$ and H$β$ from excited hydrogen H I* $n=2$ level, which are rarely seen in quasar spectra. We identify two components in the BAL troughs of $Δv\sim$2000 km s$^{-1}$ width: One component shows an identical profile in H I*, \hei* and \mgii with its centroid blueshifted by $-v_{\rm c}\approx 726$ km\ s$^{-1}$. The other component is detected in \hei* and \mgii with $-v_{\rm c}\approx 1412$ km s$^{-1}$. We estimate the column densities of H I*, He I*, and Mg II, and compare them with possible level population mechanisms. Our results favor the scenario that the Balmer BALs originate in a partially ionized region with a column density of $N_{\rm H}\sim 10^{21-22}$ cm$^{-2}$ for an electron density of $n_e\sim 10^{6-8} $cm$^{-3}$ via Ly$α$ resonant scattering pumping. The harsh conditions needed may help to explain the rarity of Balmer absorption line systems in quasar spectra. With an $i$-band PSF magnitude of 16.50, LBQS 1206+1052 is the brightest Balmer-BAL quasar ever reported. Its high brightness and unique spectral properties make LBQS 1206+1052 a promising candidate for follow-up high-resolution spectroscopy, multi-band observations, and long-term monitoring.

astro-ph.CO↗