Evolution of Star-forming Galaxies from z=0.7 to 1.2 with eBOSS Emission-line Galaxies

We study the evolution of star-forming galaxies with 10(10)M(circle dot) < M-* < 10(11.6)M(circle dot) over the redshift range of 0.7 < z < 1.2 using the emission-line galaxies (ELGs) in the extended Baryon Oscillation Spectroscopic Survey (eBOSS). By applying the incomplete conditional stellar mass function (SMF) model proposed in Guo et al., we simultaneously constrain the sample completeness, the stellar-halo mass relation (SHMR), and the quenched galaxy fraction. We obtain the intrinsic SMFs for star-forming galaxies in the redshift bins of 0.7 < z < 0.8, 0.8 < z < 0.9, 0.9 < z < 1.0, and 1.0 < z < 1.2, as well as the SMF for all galaxies in the redshift bin of 0.7 < z

NEAR-ULTRAVIOLET SPECTROSCOPY OF STAR-FORMING GALAXIES FROM eBOSS: SIGNATURES OF UBIQUITOUS GALACTIC-SCALE OUTFLOWS

Johan Comparat, Timothée Guy Olivier Delubac, Jean-Paul Richard Kneib, Jeffrey Newman, Anand Stéphane Raichoor

We present rest-frame near-ultraviolet (NUV) spectroscopy of star-forming galaxies (SFGs) at 0.6 < z < 1.2 from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) in SDSS-IV. One of the eBOSS programs is to obtain 2 ''. (about 15 kpc) fiber spectra of about 200,000 emission-line galaxies (ELGs) at redshift z greater than or similar to 0.6. We use the data from the pilot observations of this program, including 8620 spectra of SFGs at 0.6 < z < 1.2. The median composite spectra of these SFGs at 2200 angstrom < lambda < 4000 angstrom feature asymmetric, preferentially blueshifted non-resonant emission, Fe II*, and blueshifted resonant absorption, e.g., Fe II and Mg II, indicating ubiquitous outflows driven by star formation at these redshifts. For the absorption lines, we find a variety of velocity profiles with different degrees of blueshift. Comparing our new observations with the literature, we do not observe the non-resonant emission in the small-aperture (< 40 pc) spectra of local star-forming regions with the Hubble Space Telescope, and find the observed line ratios in the SFG spectra to be different from those in the spectra of local star-forming regions, as well as those of quasar absorption-line systems in the same redshift range. We introduce an outflow model that can simultaneously explain the multiple observed properties and suggest that the variety of absorption velocity profiles and the line ratio differences are caused by scattered fluorescent emission filling in on top of the absorption in the large-aperture eBOSS spectra. We develop an observation-driven, model-independent method to correct the emission infill to reveal the true absorption profiles. Finally, we show that the strengths of both the non-resonant emission and the emission-corrected resonant absorption increase with [O II] lambda lambda 3727, 3730 rest equivalent width and luminosity, with a slightly larger dependence on the former. Our results show that the eBOSS and future dark-energy surveys (e.g., Dark Energy Spectroscopic Instrument survey and Prime Focus Spectrograph survey) will provide rich data sets of rest-frame NUV spectroscopy for astrophysical applications.

Iop Publishing Ltd2015

The SDSS-IV extended Baryon Oscillation Spectroscopic Survey: selecting emission line galaxies using the Fisher discriminant

Johan Comparat, Timothée Guy Olivier Delubac, Zhe Jiang, Jean-Paul Richard Kneib, Anand Stéphane Raichoor, Jian Wang, Xiaoqing Zhou

We present a new selection technique of producing spectroscopic target catalogues for massive spectroscopic surveys for cosmology. This work was conducted in the context of the extended Baryon Oscillation Spectroscopic Survey (eBOSS), which will use similar to 200 000 emission line galaxies (EEGs) at 0.6 < z(spec),, < 1.0 to obtain a precise baryon acoustic oscillation measurement. Our proposed selection technique is based on optical and near-infrared broad-band filter photometry. We used a training sample to define a quantity, the Fisher discriminant (linear combination of colours), which correlates best with the desired properties of the target: redshift and [OII] flux. The proposed selections are simply done by applying a cut on magnitudes and this Fisher discriminant. We used public data and dedicated SDSS spectroscopy to quantify the redshift distribution and [0111 flux of our ELG target selections. We demonstrate that two of our selections fulfil the initial eBOSS/ELG redshift requirements: for a target density' of 180 deg(-2), similar to 70% of the selected objects have 0.6 < zspec < 1.0 and only similar to 1% of those galaxies in the range 0.6 < zspec < 1.0 are expected to have a catastrophic z(spec) estimate. Additionally, the stacked spectra and stacked deep images for those two selections show characteristic features of star -forming galaxies. The proposed approach using the Fisher discriminant could, however, be used to efficiently-select other galaxy populations, based on multi-band photometry, providing that spectroscopic information is available. This technique could thus be useful for other future massive spectroscopic surveys such as PFS, DESI, and 4MOST.

Edp Sciences S A2016

Cold gas in the cosmic web around galaxy clusters

Damien Louis Alexandre Spérone-Longin

Galaxies live in very different types of environment. Those different environments are relics from the evolution of the Universe since the Big Bang. This network of structures observed via large scale surveys is called Cosmic Web. Within this web, galaxies can be isolated, in a filament, in a group, or in a cluster. When part of a cluster of galaxies, their morphologies, gas content (cold and hot), and star formation activities is seen to be affected by other galaxies, or by the gas inside the cluster. However, the long-term effects of the local environment on galaxy evolution remain unclear. Also, it has been observed that a pre-processing is happening long before the galaxies enter the cluster cores, which could explain the build-up of the passive galaxy sequence, where galaxies have quenched star formation. The aim of this thesis is to see if and how the cold molecular gas reservoir of galaxies is modified when star formation activity is decreasing and if there is a link with the position of the galaxy in the CW around the cluster. We gathered unprecedented observations: the first and largest survey of the molecular gas content of galaxies in and around the same cluster environment at intermediate redshifts. These Atacama Large Millimeter Array observations are part of a larger survey called Spatially Extended ESO Distant Cluster Survey. We are focusing on two clusters at a redshift of 0.5, which benefit from previous deep photometric and spectroscopic observations. This will allow us to derive accurate stellar masses and star formation rates, in order to compare those galaxies to other surveys of the cold gas content of galaxies, either in the field or inside different clusters. We unveiled a new population of galaxies with normal star formation rates but less cold molecular gas than other galaxies at the same stellar mass. This could be an indication that the gas reservoir responsible for the star formation changes either in mass or properties, before the star formation is affected. We also noticed that galaxies with the lowest cold-molecular-gas-to-stellar-mass ratios are preferentially either in the cluster core or in overdensities away from the cluster, confirming the existence of a pre-processing in overdensities surrounding the cluster. But active galaxies inside or close to the cluster, do not always have depleted CO reservoir. This thesis opens up new prospects on the study of the cold gas content of galaxies at intermediate redshift. It showed the necessity to observe galaxies that are in a transition regime between star forming and passive, in order to understand how star formation is suppressed around clusters. Those results could be extended to much larger samples, with the help of the upcoming new generation of instruments such as the Square Kilometer Array.