WAVES: A dark matter experiment

2016-11-29

For the majority of time (10 of 13.8 Gyrs) dark matter has been the dominant influence in our Universe, driving both the decelerating expansion over the first 10 billion years, as well as clumping and coalescing under gravitational attraction into the super-clusters, filaments, and halos that make up the cosmic web. As the dark matter clumps, the baryons are drawn in, leading to self-gravitating baryonic structures in which star-formation, nucleosynthesis beyond Helium, and complex structures such as you and I emerge. Dark matter is arguably the most critical component of our Universe, and certainly played the most important role in shaping its large-scale structure today. Direct searches for dark matter have thus far failed to identify the underlying particle(s), and so we continue to study it indirectly via its gravitational interaction with normal matter, and through the bending of light around mass concentrations. From a cosmological perspective we have several ways of quantifying the total amount of dark matter, in particular: SNIa (one Nobel prize), the CMB (two Nobel prizes), massive cluster dynamics, weak lensing, and redshift space distortions. These quantify the total amount of dark matter, and contain statistical information as to its spatial distribution and halo mass distribution, but do not trace all of the individual concentrations themselves.

Numerical simulations suggest the dark matter mass distribution follows a simple power law with the majority of mass clumped in halos comparable in mass to the local Milky Way group, i.e., ~10^12 Msol. The only method that allows us to trace the dark matter condensates directly to this mass resolution is group finding. Here we rely on the random motions of the bound galaxies to relay the underlying halo mass and profile shape. To do this well requires a very specific survey design; one which is extensive in area yet fully sampled and highly complete, and with a velocity precision of ~30km/s. 4MOST is the only facility capable of delivering on this with its high multiplexing capability, coupled to its broad field of view, R>2500 resolution, and dedicated operational mode.

WAVES will allow us to identify 50,000 dark matter halos from very high cluster masses to local group scales in the nearby Universe, and a further 50,000 halos out to a time when the Universe was half its current age. These data will be used to study dark matter and its recent growth, as well as its influence on the galaxy formation process.

For the former we will precisely reconstruct the dark matter distribution within a ~Gpc^3 volume as well as its evolution over an 8 billion year timeline. For the latter we will study the properties of the galaxies, stars, dust and gas within these halos over the same timeline. Even more ambitiously the survey even has the potential to place meaningful constraints on the dark matter particle mass via: the incidence of pairs, the stacked halo profile shapes, and void sizes, all of which require bespoke simulations now underway at UWA. It is clear that deviations from our concordance cold dark matter model, if they exist, are best probed at the smallest (i.e. group) scales since this is where discrepancies between “warm" and “cold” power-spectra in the initial conditions of the Universe will lie.

The figure shows notable surveys from which group catalogues have been constructed with 100s to 1000s of halos. WAVES will be a ten-fold game-changer and the most extensive dark matter study for the foreseeable future. The mauve regions denote the photo-z selected WAVES-Wide regions, along with the two WAVES-Deep fields. Within these zones all dark matter condensates down to local group halos masses will be known.

News update from the Project Scientist(s)

2016-11-26

Since the All Hands Meeting in Heidelberg Project Science has been working on consolidating the Science Schedule. This has been possible thanks to the recent agreement between ESO and 4MOST regarding Phase1 and Phase2. Phase1 starts essentially just before the Call for Letters of intent to the Community and Phase 2 ends when the full 4MOST Survey Program starts. We hope to publish the schedule for Phase 0, 1, and 2 very soon as it is also needed for the Data Flow Design Review that will take place in late March 2017, in Lund, Sweden.

As of the All Hands Meeting Morgan Fouesneau has taken over as the lead for the Infrastructure Working Group 9 - Object Classification, after Gal Matijevic had to step down. Morgan is very welcome and we look forward to working with him.

Much work in the Project Science is currently, November and December 2016, focused on preparation for the Data Flow Design Review. This includes making sure that all Survey Science Plans are released as well as all relevant documentation from the Infrastructure Working Groups.

Announcement: 4MOST All Hands Meeting 2017

2016-11-18

The 4MOST All Hands Meeting 2017 will take place at CRAL in the beautiful city of Lyon on 11-15 September 2017. Please mark your calendars.

4MOST All Hands Meeting 2016

2016-09-16

The 4MOST All Hands Meeting 2016 will take place in Heidelberg on 19 – 23 September 2016. The meeting is hosted by the 4MOST team at the Landessternwarte Heidelberg.

The 4MOST facility, providing a massively multiplexed optical spectroscopy capability for the European Southern Observatory's VISTA telescope, is now in the final design phase, with on-sky surveys planned to commence in 2021. 4MOST will carry out a number of significant and transformational spectroscopic surveys which will enable significant advances in our understanding of our cosmos, from the evolution and structure of our Milky Way, to the growth of structure and evolution of the distant Universe.

The second annual 'All Hands Meeting' of the 4MOST consortium will bring together those working to define, construct, operate and scientifically exploit the 4MOST Facility. This includes the scientists from the large number of institutes involved in defining the ground breaking consortium science surveys, the applications specialists involved in the infrastructure groups, and the engineers, managers and scientists responsible for the delivery of the 4MOST Facility. All consortium members and prospective consortium members are invited to attend.

In addition to discussing ideas on the development of the 4MOST instrument and science, participants also get to visit Heidelberg with its many historic and cultural attractions, such as the romantic ruins of the castle towering above the Neckar river, Germany’s oldest university and the historic Old Town. With one of the leading universities in the world and numerous major international research institutions Heidelberg is also a city of science.

Please see http://wiki.4most.eu/all-hands-meeting-2016 for the meeting programme.

4MOST Newsletter Issue 2

2016-04-09

Before we had the News Blog, news related to the 4MOST project were published in the 4MOST Newsletter. Here is Issue 2.

4MOST Newsletter Issue 1

2015-09-09

Before we had the News Blog, news related to the 4MOST project were published in the 4MOST Newsletter. Here is Issue 1.

4MOST All Hands Meeting 2015

2015-07-15

Location: Institute of Astronomy, University of Cambridge, UK

Dates: 28 Sept - 2 Oct 2015

The 4MOST facility, providing a massively multiplexed optical spectroscopy capability for the European Southern Observatory's VISTA telescope, is now in the design phase, with on sky survey's planned to commence in 2021. 4MOST will carry out a number of significant and transformational spectroscopic survey's which will enable significant advances in our understanding of our cosmos, from the evolution and structure of our Milky Way, to the growth of structure and evolution of the distant Universe.

This first 'All Hands Meeting' of the 4MOST consortium, will bring together those working to define, construct, operate and scientifically exploit the 4MOST Facility. This includes the scientists from the large number of institutes involved in defining the ground breaking consortium science survey's, the applications specialists involved in the infrastructure groups, and the engineers, managers and scientists responsible for the delivery of the 4MOST Facility. All consortium members and prospective consortium members are invited to attend.

The meeting will take place over five days. The first day will focus on the key science topics to be addressed by the 4MOST Project, together with a description of the 4MOST Facility. The following days will be devoted to plenary and parallel sessions involving the survey and infrastructure working groups, the operational model for 4MOST, interface discussions between the different engineering, operations, and science subsystems, planning meetings of management and oversight bodies, and in general preparation for PDR. The last day (closing by 2pm) will enable feedback from the various parallel sessions and a look ahead to the next development period of 4MOST.

All involved with 4MOST are encouraged to reserve these dates and aim to attend. Registration and payment of the £100 registration fee are arranged through the 4MOST wiki page at http://wiki.4most.eu/all-hands-meeting-2015 (please contact Diana Johl djohl@aip.de in case you have no wiki access and are (prospective) Consortium member). Here you will also find details about accommodation and travel, and a preliminary meeting agenda.

Looking forward to seeing you all in Cambridge in September 2015.