We use 47 gravitational wave sources from the Third LIGO–Virgo–Kamioka Gravitational Wave Detector Gravitational Wave Transient Catalog (GWTC–3) to estimate the Hubble parameter H(z), including its current value, the Hubble constant H 0. Each gravitational wave (GW) signal provides the luminosity distance to the source, and we estimate the corresponding redshift using two methods: the redshifted masses and a galaxy catalog. Using the binary black hole (BBH) redshifted masses, we simultaneously infer the source mass distribution and H(z). The source mass distribution displays a peak around 34 M ⊙, followed by a drop-off. Assuming this mass scale does not evolve with the redshift results in a H(z) measurement, yielding H 0 = 68 − 8 + 12 km s − 1 Mpc − 1 (68% credible interval) when combined with the H 0 measurement from GW170817 and its electromagnetic counterpart. This represents an improvement of 17% with respect to the H 0 estimate from GWTC–1. The second method associates each GW event with its probable host galaxy in the catalog GLADE+, statistically marginalizing over the redshifts of each event’s potential hosts. Assuming a fixed BBH population, we estimate a value of H 0 = 68 − 6 + 8 km s − 1 Mpc − 1 with the galaxy catalog method, an improvement of 42% with respect to our GWTC–1 result and 20% with respect to recent H 0 studies using GWTC–2 events. However, we show that this result is strongly impacted by assumptions about the BBH source mass distribution; the only event which is not strongly impacted by such assumptions (and is thus informative about H 0) is the well-localized event GW190814.

We have used the 15‐m Swedish European Southern Observatory (ESO) Submillimetre Telescope (SEST) to observe the J= 1 → 0 and J= 2 → 1 transition lines of CO in 30 Southern hemisphere Seyfert galaxies from the extended 12‐μm sample of Rush, Malkan & Spinoglio. We detected CO J= 1 → 0 in 16 out of the 30 Seyfert galaxies and CO J= 2 → 1 in 17 out of the 30 Seyfert galaxies. From the observed spectra, various CO gas properties have been derived including the luminosity of the CO gas and, using a standard conversion factor, the H2 mass. The average H2 gas mass for Seyfert 1 galaxies was 3 × 109 M⊙ for CO J= 1 → 0 and 1 × 109 M⊙ for CO J= 2 → 1, while in comparison the H2 gas mass for Seyfert 2 type galaxies was 11 × 109 M⊙ for CO J= 1 → 0 and 3 × 109 M⊙CO J= 2 → 1. From this small sample of Seyfert galaxies, we tentatively support the conclusion that type 2 Seyfert galaxies contain more molecular gas than their type 1 counterparts.

We present results from the first successful open call e-VLBI science run, observing the X-ray binary GRS 1915+105. e-VLBI science allows the rapid production of VLBI radio maps, within hours of an observation rather than weeks, facilitating a decision for follow-up observations. A total of 6 telescopes observing at 5 GHz across the European VLBI Network (EVN) were correlated in real time at the Joint Institute for VLBI in Europe (JIVE). Constant data rates of 128 Mbps were transferred from each telescope, giving 4 TB of raw sampled data over the 12 hours of the whole experiment. Throughout this, GRS 1915+105 was observed for a total of 5.5 hours, producing 2.8 GB of visibilities of correlated data. A weak flare occurred during our observations, and we detected a slightly resolved component of 2.7 x 1.2 milliarcsecond with a position angle of 140 (+/-2) degrees. The peak brightness was 10.2 mJy per beam, with a total integrated radio flux of 11.1 mJy.Comment: Accepted for publication in MNRAS 4 pages, 3 figure