COSMIC WEB AND STAR FORMATION ACTIVITY IN GALAXIES ATz∼ 1

Abstract

We investigate the role of the delineated cosmic web/filaments on the star formation activity by exploring a sample of 425 narrow-band selected Hα emitters, as well as 2846 color-color selected underlying star-forming galaxies for a large scale structure (LSS) at z=0.84 in the COSMOS field from the HiZELS survey. Using the scale-independent Multi-scale Morphology Filter (MMF) algorithm, we are able to quantitatively describe the density field and disentangle it into its major components: fields, filaments and clusters. We show that the observed median star formation rate (SFR), stellar mass, specific star formation rate (sSFR), the mean SFR-Mass relation and its scatter for both Hα emitters and underlying star-forming galaxies do not strongly depend on different classes of environment, in agreement with previous studies. However, the fraction of Hα emitters varies with environment and is enhanced in filamentary structures at z∼1. We propose mild galaxy-galaxy interactions as the possible physical agent for the elevation of the fraction of Hα star-forming galaxies in filaments. Our results show that filaments are the likely physical environments which are often classed as the "intermediate" densities, and that the cosmic web likely plays a major role in galaxy formation and evolution which has so far been poorly investigated.

CF-HiZELS, an ∼10 deg2 emission-line survey with spectroscopic follow-up: Hα, [O iii] + Hβ and [O ii] luminosity functions at z = 0.8, 1.4 and 2.2

“…In practice, the structure is likely a dense cosmic web structure or filamentary/wall-like as a group. Darvish et al (2014) find that the fraction of star-forming galaxies (Hα emitters) is much higher in filaments than in the general field or in clusters, making these easily detectable with wide Hα surveys.…”

A 16 deg2 survey of emission-line galaxies at z < 1.5 in HSC-SSP Public Data Release 1

“…As a first step to address these important issues for understanding galaxy evolution, a more comprehensive sampling of star-forming galaxies at the redshifts of z < ∼ 3 is required that covers a wide range in terms of star formation activity and environment. Recent studies have indeed demonstrated the importance of investigating galaxy properties along the cosmic web (e.g., Darvish et al 2014;Darvish et al 2015;Darvish et al 2016;Darvish et al 2017;Malavasi et al 2017;Laigle et al 2017;Kuutma et al 2017). …”

SPECTROSCOPIC STUDY OF STAR-FORMING GALAXIES IN FILAMENTS AND THE FIELD ATz∼ 0.5: EVIDENCE FOR ENVIRONMENTAL DEPENDENCE OF ELECTRON DENSITY

“…Although they are expected to occupy 10% of the volume of the cosmic web, simulations have shown that galaxy filaments contain most of the mass in the universe (∼40%;Aragón-Calvo et al 2010) and host a significant fraction of baryons in the form of a warm-hot intergalactic medium gas in the temperature range 10 5 -10 7 K (Cen & Ostriker 1999Davé et al 2001Davé et al , 2010Klar & Mücket 2012). Filaments are seen in the optical wavelengths as the large-scale thread-like concentration of galaxies (e.g., Pimbblet et al 2004;Scoville et al 2007aScoville et al , 2013Kovač et al 2010;Guzzo & The Vipers Team 2013;Alpaslan et al 2014;Darvish et al 2014Darvish et al , 2015Tempel et al 2014), in X-ray as a warm-hot gas in emission and absorption (e.g., Scharf et al 2000;Zappacosta et al 2002Zappacosta et al , 2010Finoguenov et al 2003;Kaastra et al 2003;Nicastro et al 2005aNicastro et al , 2005bNicastro et al , 2010Werner et al 2008;Danforth et al 2010), in the infrared as possible sites of enhanced star-formation activity, linking clusters (e.g., Koyama et al 2008;Biviano et al 2011;Coppin et al 2012;Pintos-Castro et al 2013), and in the weak-lensing studies as a bridging distribution of dark matter, connecting galaxy clusters (e.g., Dietrich et al 2012;Jauzac et al 2012;Higuchi et al 2015).…”

“…Nevertheless, the limited number of studies in this field has already highlighted the importance of filaments as regions with an enhanced fraction of star-forming galaxies and/or star-formation activity (Porter & Raychaudhury 2007;Fadda et al 2008;Koyama et al 2008;Porter et al 2008;Biviano et al 2011;Coppin et al 2012;Pintos-Castro et al 2013;Darvish et al 2014). There are also some systematic surveys/works trying to expand galaxy evolution studies beyond the cluster realm by probing the much larger scale structures (of the order of ∼10 Mpc and beyond) around massive galaxy cluster candidates (see, e.g., Kodama et al 2005;Kartaltepe et al 2008;Lubin et al 2009;Sobral et al 2011).…”