Feed aggregator

arXiv:2404.10751v1 Announce Type: new Abstract: We present an analysis of rest-frame UV continuum slopes, $\beta$, using a sample of 1011 galaxies at $6.5

arXiv:2404.10040v1 Announce Type: new Abstract: The increasingly neutral intergalactic gas at $z>6$ impacts the Lyman-$\alpha$ flux observed from galaxies. One luminous galaxy, COLA1, stands out because of its unique double-peaked Ly$\alpha$ line at $z=6.6$, unseen in any simulation of reionization. Here we present JWST/NIRCam wide-field slitless spectroscopy in a 21 arcmin$^2$ field centered on COLA1. We find 141 galaxies spectroscopically-selected through the [OIII]($\lambda4969,5008$) doublet at $5.35M_{\rm UV}>-19.5$).

arXiv:2310.12330v2 Announce Type: replace Abstract: Understanding the co-evolution of supermassive black holes (SMBHs) and their host systems requires a comprehensive census of active galactic nuclei (AGN) behavior across a wide range of redshift, luminosity, obscuration level and galaxy properties. We report significant progress with JWST towards this goal from the Systematic Mid-infrared Instrument Legacy Extragalactic Survey (SMILES). Based on comprehensive SED analysis of 3273 MIRI-detected sources, we identify 217 AGN candidates over a survey area of $\sim$34 arcmin$^2$, including a primary sample of 111 AGNs in normal massive galaxies ($M_{*}>10^{9.5}~M_\odot$) at $z\sim$0--4, an extended sample of 86 AGN {\it candidates} in low-mass galaxies ($M_{*}

arXiv:2404.10811v1 Announce Type: new Abstract: The James Webb Space Telescope (JWST) is revolutionizing our understanding of black holes formation and growth in the early Universe. However, JWST has also revealed that some of the classical diagnostics, such as the BPT diagrams and X-ray emission, often fail to identify narrow line TypeII active galactic nuclei (AGN) at high redshift. Here we present three new rest-frame optical diagnostic diagrams leveraging the [OIII]$\lambda4363$ auroral line, which has been detected in several JWST spectra. Specifically, we show that high values of the [OIII]$\lambda4363/$H$\gamma$ ratio provide a sufficient (but not necessary) condition to identify the presence of an AGN, both based on empirical calibrations (using local and high-redshift sources) and a broad range of photoionization models. These diagnostics are able to separate much of the AGN population from Star Forming Galaxies (SFGs). This is because the average energy of AGN's ionizing photons is higher than that of young stars in SFGs, hence AGN can more efficiently heat the gas, therefore boosting the [OIII]$\lambda4363$ line. We also found independent indications of AGN activity in some high-redshift sources that were not previously identified as AGN with the traditional diagnostics diagrams, but that are placed in the AGN region of the diagnostics presented in this work. We note that, conversely, low values of [OIII]$\lambda4363/$H$\gamma$ can be associated either with SFGs or AGN excitation. We note that the fact that strong auroral lines are often associated with AGN does not imply that they cannot be used for direct metallicity measurements (provided that proper ionization corrections are applied), but it does affect the calibration of strong line metallicity diagnostics.

The Via Project: Mapping the invisible Galactic halo

Abstract not available

• Speaker: Ana Bonaca (Carnegie)
• Friday 26 April 2024, 11:30-12:30
• Venue: Ryle seminar room + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

Add to your calendar or Include in your list

The Dark Energy Spectroscopic Instrument (DESI) Year 1 Results: Baryon Acoustic Oscillations and implications for cosmology

DESI represents the culmination of multi-years efforts and advanced spectroscopic techniques. Placed at Mayall 4-meter Telescope, DESI harnesses the power of 5,000 robotic fiber positioners, coupled with state-of-the-art spectrographs, to capture the spectral signatures of millions of galaxies and quasars with unprecedented precision. DESI success is also based on the collaborative spirit of its community, more than 400 scientists over 72 institutions. This data release corresponds to the first year of observations; it holds immense scientific promise across a multitude of fronts: from constraining cosmological parameters, mapping the expansion history of the Universe, to the properties of dark energy and the properties of neutrinos. So far only Baryon Acoustic Oscillations (BAO) information has been fully analysed and made public. I will summarise the main findings and the implications for cosmology.

• Speaker: Licia Verde (University of Barcelona)
• Monday 22 April 2024, 13:00-14:00
• Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
• Series: Cosmology Lunch; organiser: Fiona McCarthy.

Add to your calendar or Include in your list

Title to be confirmed

Abstract not available

• Speaker: Ana Bonaca (Carnegie)
• Friday 26 April 2024, 11:30-12:30
• Venue: Ryle seminar room + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

Add to your calendar or Include in your list

Title to be confirmed

Abstract not available

• Speaker: Rajsekhar Mohapatra (Princeton)
• Friday 10 May 2024, 11:30-12:30
• Venue: Ryle seminar room + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

Add to your calendar or Include in your list

Which universes does the no-boundary wave function favour?

Please notice the unusual schedule (9:45am) and location (MR9) due to previous overlaps with the Dirac lunch and Dirac lecture.

• Speaker: Jean-Luc Lehners (MPI for Gravitational Physics, Potsdam)
• Monday 13 May 2024, 09:45-10:45
• Venue: CMS, Pav. B, MR9 (B0.09) .
• Series: Cosmology Lunch; organiser: Thomas Colas.

Add to your calendar or Include in your list

Which universes does the no-boundary wave function favour?

Please notice the unusual schedule due to previous overlaps with the Dirac lunch and Dirac lecture.

• Speaker: Jean-Luc Lehners (MPI for Gravitational Physics, Potsdam)
• Monday 13 May 2024, 09:45-10:45
• Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
• Series: Cosmology Lunch; organiser: Thomas Colas.

Add to your calendar or Include in your list

arXiv:2404.09825v1 Announce Type: new Abstract: We use Legacy Survey photometric data to probe the stellar halo in multiple directions of the sky using a probabilistic methodology to identify Blue Horizontal Branch (BHB) stars. The measured average radial density profile follows a double power law in the range $ 5

arXiv:2404.08910v1 Announce Type: new Abstract: We present a detailed study of the centre of NGC4654, a Milky Way-like spiral galaxy in the Virgo cluster that has been reported to host a double stellar nucleus, thus promising a rare view of ongoing star cluster infall into a galaxy nucleus. Analysing JWST NIRSpec integral-field spectroscopic data and Hubble Space Telescope imaging of the inner 330 $\times$ 330 pc, we find that the nucleus harbours in fact three massive star clusters. Maps of infrared emission lines from NIRSpec show different morphologies for the ionised and molecular gas components. The emission from molecular hydrogen gas is concentrated at the NSC location, while emission from hydrogen recombination lines is more extended beyond the central cluster. The velocity fields of both gas and stars indicate that the three clusters are part of a complicated dynamical system, with the NSC having an elevated velocity dispersion in line with its high stellar mass. To investigate the stellar populations of the three clusters in more detail, we use surface brightness modelling to measure their fluxes from ultraviolet to mid-infrared wavelengths and fit their spectral energy distributions (SEDs). Two of the clusters are UV-bright and well described by single stellar populations with young ages ($\sim$ 3 and 5 Myr) and low masses ($M_\ast \sim 4 \times 10^{4} - 10^{5} M_\odot$), whereas the central cluster is much more massive ($3 \times 10^7 M_\odot$), and cannot be fitted by a single stellar population. Instead, we find that a minor young population ($\sim$ 1 Myr) embedded in a dominant old population ($\sim$ 8 Gyr) is needed to explain its SED. Given its complex composition and the close proximity of two young star clusters that are likely to merge with it within a few hundred million years, we consider NGC4654 a unique laboratory to study NSC growth from both in-situ star formation and the infall of star clusters.

The renowned scientist came up with revolutionary ideas in the 1960s, sparking a 50-year search for evidence.

Nature, Published online: 15 April 2024; doi:10.1038/d41586-024-01115-3

New results could help to end a long standing disagreement over the rate of cosmic expansion. But scientists say more measurements are needed.

Studies of the reionization-era intergalactic and circumgalactic media using cosmological simulations

TBC

• Speaker: Dr. Caitlin Doughty (University of Leiden/MPA Garching)
• Tuesday 22 October 2024, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

Add to your calendar or Include in your list

The ionising properties of galaxies at the Epoch of Reionisation with JWST

TBC

• Speaker: Dr. Charlotte Simmonds (Kavli Institute for Technology, University of Cambridge)
• Tuesday 11 June 2024, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

Add to your calendar or Include in your list

The Black Hole Mass Metallicity Relation and Insights into Galaxy Quenching

TBC

• Speaker: William Baker (University of Cambridge)
• Tuesday 28 May 2024, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

Add to your calendar or Include in your list

Liquid Crystal based adaptive optics

TBC

• Speaker: Oana Niculescu (University of Cambridge)
• Tuesday 14 May 2024, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

Add to your calendar or Include in your list

Interferometric measurements of the 21-cm signal with SKA

The Cosmic Dawn marks the first star formations and preceded the Epoch-of-Reionization, when the Universe underwent a fundamental transformation propelled by the radiation from these first stars and galaxies. Interferometric 21-cm experiments aim to probe redshifted neutral hydrogen signals from these periods, constraining the conditions of the early Universe. The SKA -LOW instrument of the Square Kilometre Array telescope is envisaged to be the largest and most sensitive radio telescope at m and cm wavelengths. In this talk we present a data analysis pipeline that was used in the SKA Science Data Challenge 3a: Epoch of Reionisation (SKA SDC3a) to process the novel data products expected from the SKA . To determine whether a successful 21-cm detection is possible with the envisaged SKA , we implement predictive foreground and Bayesian Gaussian Process Regression models alongside a foreground avoidance strategy to isolate the 21-cm signal from that of the astrophysical radio frequency (RF) foregrounds.

• Speaker: Yuchen Liu and Oscar O'Hara (Cavendish Astrophysics)
• Tuesday 07 May 2024, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

Add to your calendar or Include in your list

Radio observations of extra-galactic transients with the AMI-LA telescope

TBC

• Speaker: Dr. Lauren Rhodes (University of Oxford)
• Tuesday 30 April 2024, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

Add to your calendar or Include in your list