Search

Changing-look active galactic nuclei (CLAGN) are AGN that change type as their broad emission lines appear or disappear, which is usually accompanied by strong flux changes in their blue featureless continuum. We search for turn-on CLAGN by selecting type-2 AGN from the spectroscopic Six-degree Field Galaxy Survey (6dFGS), whose colours, observed ∼15 yr later by the SkyMapper Southern Survey, are suggestive of type-1 AGN. Starting from 1092 type-2 AGN, we select 20 candidates for follow-up and confirm that 14 of them have changed into type-1 and are thus turn-on CLAGN; further observations reveal 11 more turn-on CLAGN. While our search was not tailored to efficiently discover turn-off CLAGN, we discover two such cases as well. The result suggests a turn-on CLAGN rate of over 3 per cent over ∼15 yr and imply a total CLAGN rate of more than ∼6 per cent over this period. Finally, we present observations of AGN that are atypical for the CLAGN phenomenology, including J1109146 – a type-1 that did not appear as an AGN at all in 6dFGS; J1406507 – the second reported changing-look narrow-line Seyfert 1; and J1340153 – a CLAGN with a change time-scale of 3 months.

We report the discovery of a bright (g = 14.5 mag (AB), K = 11.9 mag (Vega)) quasar at redshift z = 0.83 -- the optically brightest (unbeamed) quasar at z > 0.4. SMSS J114447.77-430859.3, at a Galactic latitude of b = +18.1deg, was identified by its optical colours from the SkyMapper Southern Survey (SMSS) during a search for symbiotic binary stars. Optical and near-infrared spectroscopy reveals broad MgII, H-beta, H-alpha, and Pa-beta emission lines, from which we measure a black hole mass of log10(M_BH/M_Sun) = 9.4 +/- 0.5. With its high luminosity, L_bol = (4.7 +/- 1.0) * 10^47 erg/s or M_i(z=2) = -29.74 mag (AB), we estimate an Eddington ratio of ~1.4. As the most luminous quasar known over the last ~9 Gyr of cosmic history, having a luminosity 8 times greater than 3C 273, the source offers a range of potential follow-up opportunities., 13 pages. Accepted for publication in PASA

Changing look active galactic nuclei (CLAGNs) are rare cases of AGNs, where the continuum flux increases/decreases and the broad emission lines appear/disappear within short time-scales. These extreme changes challenge our understanding of accretion disc dynamics. We present a sample of four new CLAGNs at 0.026 < z < 0.107, which were found by cross-matching the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey with AGNs from the SDSS spectroscopic data base. Our results show that the selection criteria of $\gt \mathopen |0.5\mathclose |$ mag change in SDSS-g band is ineffective at lower redshifts. This is, in part, due to the fact that the g band is probing a different part of the AGNs spectral energy distribution at these redshifts. The bigger issue is that the galaxy continuum dominates the spectrum and thus overwhelms any variation of the AGNs continuum that might contribute to photometric variations. This suggests the need to use different methods for future low-redshift CLAGNs searches.

We describe the first results from the All-sky BRIght, Complete Quasar Survey (AllBRICQS), which aims to discover the last remaining optically bright quasars. We present 156 spectroscopically confirmed quasars (140 newly identified) having |b|>10deg. 152 of the quasars have Gaia DR3 magnitudes brighter than B_P=16.5 or R_P=16 mag, while four are slightly fainter. The quasars span a redshift range of z=0.07-3.93. In particular, we highlight the properties of J0529-4351 at z=3.93, which, if unlensed, is one of the most intrinsically luminous quasars in the Universe. The AllBRICQS sources have been selected by combining data from the Gaia and WISE all-sky satellite missions, and we successfully identify quasars not flagged as candidates by Gaia Data Release 3. We expect the completeness to be approximately 96% within our magnitude and latitude limits, while the preliminary results indicate a selection purity of approximately 96%. The optical spectroscopy used for source classification will also enable detailed quasar characterisation, including black hole mass measurements and identification of foreground absorption systems. The AllBRICQS sources will greatly enhance the number of quasars available for high-signal-to-noise follow-up with present and future facilities., 33 pages. Accepted for publication in PASA. Minor edits from previous version

Quasars behind the Galactic plane (GPQs) are important astrometric references and valuable probes of Galactic gas, yet the search for GPQs is difficult due to severe extinction and source crowding in the Galactic plane. In this paper, we present a sample of 204 spectroscopically confirmed GPQs at |b, Comment: 17 pages, 10 figures, published in ApJS. Tables and spectra in this paper are available at https://doi.org/10.12149/101095

We search for ultra-luminous Quasi-Stellar Objects (QSOs) at high redshift using photometry from the SkyMapper Southern Survey Data Release 3 (DR3), in combination with 2MASS, VHS DR6, VIKING DR5, AllWISE, and CatWISE2020, as well as parallaxes and proper motions from Gaia DR2 and eDR3. We report 142 newly discovered Southern QSOs at $3.880$ per cent complete for $M_{145}, Comment: 25 pages. Resubmitted to MNRAS after significant revisions. 23 new QSOs added; overhaul of methodology; important changes to results

We study the utility of broad-band colours in the SkyMapper Southern Survey for selecting Seyfert galaxies at low luminosity. We find that the $u-v$ index, built from the ultraviolet $u$ and violet $v$ filters, separates normal galaxies, starburst galaxies and type-1 AGN. This $u-v$ index is not sensitive to age or metallicity in a stellar population but is instead a quenching-and-bursting indicator in galaxies and detects power-law continua in type-1 AGN. Using over 25,000 galaxies at $z, Accepted for publication in MNRAS

The most luminous quasars at high redshift harbour the fastest-growing and most massive black holes in the early Universe. They are exceedingly rare and hard to find. Here, we present our search for the most luminous quasars in the redshift range from $z=4.5$ to $5$ using data from SkyMapper, Gaia and WISE. We use colours to select likely high-redshift quasars and reduce the stellar contamination of the candidate set with parallax and proper motion data. In $\sim$12,500~deg$^2$ of Southern sky, we find 92 candidates brighter than $R_p=18.2$. Spectroscopic follow-up has revealed 21 quasars at $z\ge 4$ (16 of which are within $z=[4.5,5]$), as well as several red quasars, BAL quasars and objects with unusual spectra, which we tentatively label OFeLoBALQSOs at redshifts of $z\approx 1$ to $2$. This work lifts the number of known bright $z\ge 4.5$ quasars in the Southern hemisphere from 10 to 26 and brings the total number of quasars known at $R_p, Comment: Submitted to MNRAS, 10 pages

We report the discovery of the ultra-luminous QSO SMSS~J215728.21-360215.1 with magnitude $z=16.9$ and W4$=7.42$ at redshift 4.75. Given absolute magnitudes of $M_{145,\rm AB}=-29.3$, $M_{300,\rm AB}=-30.12$ and $\log L_{\rm bol}/L_{\rm bol,\odot} = 14.84$, it is the QSO with the highest unlensed UV-optical luminosity currently known in the Universe. It was found by combining proper-motion data from Gaia DR2 with photometry from SkyMapper DR1 and the Wide-field Infrared Survey Explorer (WISE). In the Gaia database it is an isolated single source and thus unlikely to be strongly gravitationally lensed. It is also unlikely to be a beamed source as it is not discovered in the radio domain by either NVSS or SUMSS. It is classed as a weak-emission-line QSO and possesses broad absorption line features. A lightcurve from ATLAS spanning the time from October 2015 to December 2017 shows little sign of variability., 6 pages, 4 figures, accepted for publication in PASA