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Abstract We present a high-cadence multiepoch analysis of dramatic variability of three broad emission lines (Mgii, Hβ, and Hα) in the spectra of the luminous quasar (λLλ(5100 Å) = 4.7 × 1044erg s−1) SDSS J141041.25+531849.0 atz= 0.359 with 127 spectroscopic epochs over nine years of monitoring (2013–2022). We observe anticorrelations between the broad emission-line widths and flux in all three emission lines, indicating that all three broad emission lines “breathe” in response to stochastic continuum variations. We also observe dramatic radial velocity shifts in all three broad emission lines, ranging from Δv∼ 400 km s−1to ∼800 km s−1, that vary over the course of the monitoring period. Our preferred explanation for the broad-line variability is complex kinematics in the gas in the broad-line region. We suggest a model for the broad-line variability that includes a combination of gas inflow with a radial gradient, an azimuthal asymmetry (e.g., a hot spot), superimposed on the stochastic flux-driven changes to the optimal emission region (“line breathing”). Similar instances of line-profile variability due to complex gas kinematics around quasars are likely to represent an important source of false positives in radial velocity searches for binary black holes, which typically lack the kind of high-cadence data we analyze here. The long-duration, wide-field, and many-epoch spectroscopic monitoring of SDSS-V BHM-RM provides an excellent opportunity for identifying and characterizing broad emission-line variability, and the inferred nature of the inner gas environment, of luminous quasars.
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A Broad Line-width, Compact, Millimeter-bright Molecular Emission Line Source near the Galactic Center
Abstract A compact source, G0.02467–0.0727, was detected in Atacama Large Millimeter/submillimeter Array 3 mm observations in continuum and very broad line emission. The continuum emission has a spectral indexα≈ 3.3, suggesting that the emission is from dust. The line emission is detected in several transitions of CS, SO, and SO2and exhibits a line width FWHM ≈ 160 km s−1. The line profile appears Gaussian. The emission is weakly spatially resolved, coming from an area on the sky ≲1″ in diameter (≲104au at the distance of the Galactic center, GC). The centroid velocity isvLSR≈ 40–50 km s−1, which is consistent with a location in the GC. With multiple SO lines detected, and assuming local thermodynamic equilibrium (LTE) conditions, the gas temperature isTLTE= 13 K, which is colder than seen in typical GC clouds, though we cannot rule out low-density, subthermally excited, warmer gas. Despite the high velocity dispersion, no emission is observed from SiO, suggesting that there are no strong (≳10 km s−1) shocks in the molecular gas. There are no detections at other wavelengths, including X-ray, infrared, and radio. We consider several explanations for the millimeter ultra-broad-line object (MUBLO), including protostellar outflow, explosive outflow, a collapsing cloud, an evolved star, a stellar merger, a high-velocity compact cloud, an intermediate-mass black hole, and a background galaxy. Most of these conceptual models are either inconsistent with the data or do not fully explain them. The MUBLO is, at present, an observationally unique object.
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- PAR ID:
- 10512716
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal Letters
- Volume:
- 968
- Issue:
- 1
- ISSN:
- 2041-8205
- Format(s):
- Medium: X Size: Article No. L11
- Size(s):
- Article No. L11
- Sponsoring Org:
- National Science Foundation
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