The link between submillimetre galaxies and luminous ellipticals: near-infrared IFU spectroscopy of submillimetre galaxies

Abstract

We present two‐dimensional spectroscopy covering the rest‐frame wavelengths of strong optical emission lines in six luminous submillimetre galaxies (SMGs) at z= 1.3–2.5. Using this near‐infrared integral field spectroscopy together with Hubble Space Telescope ACS and NICMOS imaging, we map the dynamics and morphologies of these systems on scales from 4–11 kpc. Four of the systems show multiple components in their spatially resolved spectra with average velocity offsets of ∼180 km s−1 across 8 kpc in projection. From the ensemble properties of eight galaxies, from our survey and the literature, we estimate the typical dynamical masses of bright SMGs as 5 ± 3 × 1011 M⊙. This is similar to recent estimates of their stellar masses – suggesting that the dynamics of the central regions of these galaxies are baryon dominated, with a substantial fraction of those baryons in stars by the epoch of observation. Combining our dynamical mass estimates with stellar luminosities for this population, we investigate whether SMGs can evolve on to the Faber–Jackson (FJ) relation for local ellipticals. Adopting a typical lifetime of τburst∼ 300 Myr for the submillimetre‐luminous phase – using the latest estimates of gas masses, star formation rates and active galactic nucleus contribution to the bolometric luminosities – we find that the stellar populations of SMGs should fade to place them on the FJ relation, at MK∼−25.1. Furthermore, using the same starburst lifetime we correct the observed space density of SMGs for the duty cycle to derive a volume density of the progenitors of ∼1 × 10−4 Mpc−3. This is consistent with the space density of local luminous early‐type galaxies with MK∼−25.1, indicating that SMGs can evolve on to the scaling relations observed for local early‐type galaxies, and the observed population at z∼ 2 is then sufficient to account for the formation of the whole population of ≳3 L*K ellipticals seen at z∼ 0.

Dusty star-forming galaxies at high redshift

“…While complementary work at radio wavelengths using the high-resolution MERLIN interferometer Biggs & Ivison, 2008;Casey et al, 2009a) corroborate the high-J molecular gas size measurements with sizes of r e ≈2 kpc measured for radio continuum emission, we note that extended emission could either be resolved out from earlier MERLIN results or the radio continuum is only probing areas of dense star formation with higher incidents of supernovae (see § 5.12 for a discussion of radio emission in DSFGs). Furthermore, these works also found that SMG sizes were diverse, from unresolved point-sources near the Eddington starburst limit, to sources Figure 29: Line-profile characteristics of resolved Hα IFU observations of 10 SMGs (Swinbank et al, 2006;Alaghband-Zadeh et al, 2012;Menéndez-Delmestre et al, 2013). The x-axis plots velocity dispersion field asymmetry while the y-axis plots the velocity field asymmetry.…”

“…Key works on Hα kinematics in SMGs is summarized by Swinbank et al (2006), Alaghband-Zadeh et al (2012) and Menéndez-Delmestre et al (2013). Collectively, they observe 16 SMGs at 2.0 < z < 2.5 and present strong evidence for merger-driven histories−many at an early stage first pass, where multiple components are seen separated by ∼8 kpc and 200 km s −1 , while others are later stage single-component systems with high-dispersion and buried AGN.…”

Hidden starbursts and active galactic nuclei at 0 < z < 4 from theHerschel-VVDS-CFHTLS-D1 field: Inferences on coevolution and feedback

“…In some cases, star formation is thought to proceed in a sporadic manner, particularly at high redshifts, with undisturbed, low-level, continuous star formation being the exception in galaxies rather than the primary mechanism of building stellar Article published by EDP Sciences A90, page 1 of 39 mass (e.g., Kolatt et al 1999;Bell et al 2005;Papovich et al 2005Papovich et al , 2006Nichols et al 2012;Pacifici et al 2013). Violent episodes of star formation, known as starbursts, can dramatically alter the stellar mass of galaxies with sufficient gas reservoirs during the relatively short period that constitutes the lifetime of a starburst (typically ∼100-500 Myr; Swinbank et al 2006;Hopkins et al 2008;McQuinn et al 2009McQuinn et al , 2010bWild et al 2010; though perhaps up to ∼700 Myr for particular populations, e.g., Lapi et al 2011;Gruppioni et al 2013). Such events contribute significantly to the global star formation rate (SFR) of galaxies both in the high-redshift universe (e.g., Somerville et al 2001;Chapman et al 2005;Erb et al 2006;Magnelli et al 2009) and locally (e.g., Brinchmann et al 2004;Kauffmann et al 2004; Lee et al 2006Lee et al , 2009 and are furthermore thought to be a typical phase of evolution undergone by massive quiescent galaxies observed at low redshifts early in their formation history (e.g., Juneau et al 2005;Hickox et al 2012).…”

The clustering evolution of dusty star-forming galaxies

“…It has been speculated that SMGs could then evolve on to the scaling relations observed for massive local elliptical galaxies, based on simple arguments involving the time-scale of the burst and the ageing of the stellar population (e.g. Lilly et al 1999;Swinbank et al 2006;Simpson et al 2014), and assuming that most of the stellar mass at z = 0 is put in place during the 'SMG phase'. However, González et al (2011) present an alternative scenario in which SMGs evolve into galaxies with stellar mass ∼10 11 h −1 M at z = 0, with the SMG phase accounting for little of this stellar mass.…”