4MOST Community Surveys

Following the recommendations of the Public Survey Panel (PSP) and Observing Programmes Commitee (OPC), ESO has selected fiftheen surveys to be conducted during the first five years of 4MOST operations, together with the ten GTO surveys.

Galactic surveys

4MOST Gaia RRLyrae Survey (4GRoundS)
PI Rodrigo Ibata (Observatoire Astronomique de Strasbourg)

This survey aims at measuring the radial velocities and metallicities of RR Lyrae stars selected from Gaia DR3. The most accurate distances to old, distant stellar populations are those to RR Lyrae, making them invaluable dynamical tracers of the Galaxy. Their excellent photometric distances enable the exquisite Gaia proper motions to be converted into physically-useful transverse velocities. Armed with the missing radial velocity, 4GRoundS will provide the community an exquisite sample that will enable studies of the orbital structure of the halo and outer disk, and allow realistic modelling of these components. It will also enable the identification of coherent dynamically-cold streams. Together these analyses will map the mass of the Milky Way out to 100 kpc and test models of the dark sector.


4MOST survey of dwarf galaxies and their stellar streams (4DWARFS): small but fundamental.
PI Asa Skuladottir (University of Florence)

4DWARFS will target all the dwarf galaxies in the 4MOST footprint, in particular the main bodies of three large dwarf spheroidal galaxies, Sagittarius, Fornax and Sculptor. In addition, the survey will focus on the Sagittarius stream, which is a major constituent of the Galactic halo, and presents our best opportunity to observe a galaxy being currently disrupted. This survey aims at providing new and valuable insights into: 1) the properties of the first stars; 2) various nucleosynthetic channels, such as SN type Ia, AGB stars and the r-process; 3) The hierarchical galaxy formation, e.g. by quantifying the number of previous mergers in the Milky Way, and within the dwarf galaxies themselves. The survey will provide stellar ages, radial velocities and chemical abundances for 130,000 stars, and will thus increase the number of stars in dwarf galaxies and streams with detailed abundance information (>15 elements) by several orders of magnitude


Spectroscopic Discovery of Binaries with Dormant Black Holes
PI Michal Pawlak (Jagiellonian University), Tsevi Mazeh (Tel Aviv University)

This survey is a spectroscopic follow-up of the ellipsoidal binary stars discovered by the Optical Gravitational Lensing Experiment (OGLE), in order to study the short-period binary population, with periods less than 2.5 days and for discovery of dormant black holes and neutron stars in non-interacting systems. A sample of  678 in the Magellanic Clouds will be observed in order to obtain multiple radial-velocity (RV) measurements. The RVs combined with the OGLE photometry will allow for determination of the binary secondary component mass and therefore identify the compact companions.


Stellar Clusters in 4MOST.
PIs Sara Lucatello, Angela Bragaglia, Antonella Vallenari (INAF)

This survey will target 151 Globulars in the Milky Way (MW) and the Magellanic Clouds (MC) and essentially all visible MW Open Clusters and Star Forming Regions, filling the metallicity/age distribution from the [Fe/H] = −2.5 dex of GCs to super-solar OCs, from a few Myr to 13.5 Gyr. The main aims of the survey are to: understand how clusters form, evolve, dissolve, and populate the MW; calibrate complex physics that affect stellar evolution, on which our ability to measure ages ultimately stands; measure the contribution of star clusters to the formation and evolution of the individual Galactic components with unequalled precision, accuracy and statistics. The survey will be targeting ~120K stars in LRS and ~90K in HRS.


The 4MOST Survey of Young Stars (4SYS)
PI Giuseppe Germano Sacco (INAF)

This survey will identify a representative sample of ~10^5 young stars within 500 pc of the Sun, a scale that increases the number of identified young field stars and the volume explored by two orders of magnitude. 4SYS will measure stellar chemistry, 3D kinematics and ages, and use these to: trace the spatial and dynamical evolution of star forming structures as they disperse; quantify the local disk star forming rate and chemical inhomogeneity at a range of spatial scales; vastly expand the numbers of identified young stars for exoplanetary studies; and provide huge coeval samples to improve young stellar evolutionary models. This is of fundamental importance in understanding the physical processes that drive star formation, the origins of the Galactic field population and the early evolution of stars, their discs and planetary systems.


The White Dwarf Binary (WDB) survey.
PIs Odette Toloza Castillo (University of Warwick), Alberto Rebassa-Mansergas (Univeritat Politecnica de Catalunya)

This survey will use 4MOST spectroscopy to characterize the physical properties of the white dwarfs and their main sequence companions in a sample of ~100,000 white dwarf binary candidates selected from Gaia.. It comprises systems that never interacted and that are part of common proper motion pairs (CPMPs) and systems that evolved through mass transfer episodes and that are now part of close white dwarf binaries (CWDBs). On the one hand, the white dwarfs in CPMPs can be used as reliable cosmo-chronometers to independently constrain key properties of the Milky Way and its stars. On the other hand, full characterization of the many different flavours of CWDB holds the potential to observationally constrain a wide variety of key ingredients that currently hamper the validity of the theoretical models. 




4C3R2:4MOST Complete Calibration of the Color-Redshift Relation
PI Daniel Gruen (LMU)

This survey will perform a complete calibration of the ugriZYJHK color-redshift relation of galaxies with 4MOST, out to twice the redshift and down to half the stellar mass of WAVES-Deep. It will target only a representative subset of these additional galaxies, over the WAVES survey regions. This is augmented by the abundance, luminosity function, and halo occupation distribution at each point in KiDS-VIKING ugriZYJHK color-magnitude space from photometric and lensing data in KiDS/DES/ Euclid/LSST/WFIRST. With 4C3R2, 4MOST provides a complete census of galaxies to z~1.5, and 60% of the redshift calibration urgently required by future lensing surveys. 


4HS: the 4MOST Hemisphere Survey of the Nearby Universe
PI Edward Taylor, Michelle Cluver (Swinburne University of Technology)

This is a spectroscopic survey of ~5.8 million galaxies over ~17.000 deg2 of the Southern sky to produce a comprehensive census of galaxies in the z < 0.15 Universe. 4HS addresses an urgent need for uniform, wide-area, local Universe spectroscopy in the Southern hemisphere, to support European facilities, including ALMA, E-ELT, and especially SKA. The main scientific goals are 1) to map mass, motion, and the gravitational growth of structure over ~1 Gpc, approaching the fundamental limiting precision due to cosmic variance, and 2) to map galaxy demographic trends as a function of both local and large-scale environment, in order to resolve the environmental processes/effects that most influence galaxy formation and evolution.


4MOST Chilean AGN/Galaxy Evolution Survey (ChANGES).
PIs Frank Bauer (Pontificia Universidad Catolica de Chile), Paulina Lira (Universidad de Chile)

This survey will target a large sample of AGN selected from several existing surveys (ZTF, LSQ, DECam) and ultimately complemented by LSST to: 1) constrain the low-MBH, low-L/LEdd end of the accretion and BH density functions to at least z~1, and, by extension, black hole seed models; 2) investigate correlations between AGN (MBH, L/LEdd, UV slope, outflows) and host properties (stellar age, metallicity, kinematics); 3) target/confirm rare BH subsamples (lensed, extreme variable, TDEs, QSOabsorption line systems) for detailed multi-wavelength follow-up studies.


4MOST-StePS: a Stellar Population Survey using 4MOST.
PI Angela Iovino (INAF)

This survey is aiming to collect 30-hour deep spectra with 4MOST for a sample of ~3300 galaxies brighter than IAB~20.5 in the redshift range 0.3<z<0.8. These spectra - at a typical Signal to Noise Ratio SNR~30 per Å, far above all existing/ongoing surveys at intermediate redshifts - will provide a precise empirical description of the evolutionary path of massive galaxies in the yet unexplored intermediate redshift range between LEGA-C and SDSS.


4SLSLS: The 4MOST Strong Lens Spectroscopic Legacy Survey.
PI Thomas Collett (University of Portsmouth)

This survey will observe Euclid and LSST lens candidates with a source magnitude R<24 and a source photometric redshift below z_phot < 1.8, yielding 10000 spectroscopic source redshifts. It also aims at obtaining lens velocity dispersions for the 5000 brightest of these lenses. This data will enable a range of legacy science including: the stellar Initial Mass Function, constraining dark energy, testing general relativity, and highly magnified source studies4C3R2: 4MOST Complete Calibration of the Color-Redshift Relation.


CHANCES: CHileAN Cluster galaxy Evolution Survey.
PI Christopher Haines (Universidad de Atacama)

This survey is designed to study the evolution of galaxies in and around ~150 clusters over the last 4 Gyr of cosmic time. CHANCES will provide comprehensive spectroscopic coverage of massive clusters in the local Universe, pushing well beyond the virial radius to cover the surrounding infall regions as far out as 5r200 from the cluster. The survey will push cluster galaxy evolution studies to the dwarf galaxy regime where environment is expected to play a mayor role, and at the same time will harness background QSO sight lines in order to probe the effect of clusters on the gaseous content of galaxies at z>0.35.


Optical, Radio Continuum and HI Deep Spectroscopic Survey (ORCHIDSS).
PI Kenneth Duncan (University of Edinburgh)

This surey will target ~200,000 radio continuum detected objects selected from the MeerKAT deep extragalactic surveys. Using the powerful combination of radio and 4MOST spectroscopy, it will: i) provide the most reliable measurement of the evolution of the cosmic HI density and HI mass function since z=1.4; ii) measure the fundamental relations between HI and galaxy properties across a wide range of redshifts and environments for the first time; and iii) directly measure the effects of AGN and star-formationdriven feedback on regulating the neutral gas reservoirs of galaxies across cosmic time.


The 4MOST-Gaia Purely Astrometric Quasar Survey
PI Jens-Kristian Krogager (CRAL)

This survey proposes to carry out the first color-unbiased quasar survey by targeting quasars purely based on astrometry from Gaia with no assumption on spectral shape. Our survey will quantify the effect of dust-bias in intervening absorption systems at 2 < z < 3 and will provide the first large-scale and systematic analysis of quasar feedback through BAL outflows from redshift 0.8 to 4.


Transform our Understanding of the Baryon Cycle with High-Resolution Quasar Spectroscopy (ByCycle).
PI Celine Peroux (ESO)

This survey aims at using the powerful synergy of absorption and emission diagnostics by observing a sizeable sample of background quasars and foreground galaxies in the same fields. It will allow to measure the radial profile, covering fraction and optical depth of the neutral hydrogen and metals in their CGM. At high-redshift, it will build an unprecedented catalogue of Lya absorbers (DLA and LLS), measure their dust-free and ionization-corrected metallicity to reappraise the missing metals problem. Together, these results will redefine our view of the CGM and provide a definite census of the cosmic metals.