Planck’s dusty GEMS

Abstract

We present an analysis of high-resolution ALMA interferometry of CO(4-3) line emission and dust continuum in the "Ruby" (PLCK G244.8+54.9), a bright, gravitationally lensed galaxy at z= 3.0 discovered with the Planck all-sky survey. The Ruby is the brightest of Planck's Dusty GEMS, a sample of 11 of the brightest gravitationally lensed high-redshift galaxies on the extragalactic sub-mm sky. We resolve the high-surface-brightness continuum and CO line emission of the Ruby in several extended clumps along a partial, nearly circular Einstein ring with 1.4 diameter around a massive galaxy at z = 1.5. Local star-formation intensities are up to 2000 M yr −1 kpc −2 , amongst the highest observed at high redshift, and clearly in the range of maximal starbursts. Gas-mass surface densities are a few ×10 4 M pc −2 . The Ruby lies at, and in part even above, the starburst sequence in the Schmidt-Kennicutt diagram, and at the limit expected for star formation that is self-regulated through the kinetic energy injection from radiation pressure, stellar winds, and supernovae. We show that these processes can also inject sufficient kinetic energy and momentum into the gas to explain the turbulent line widths, which are consistent with marginally gravitationally bound molecular clouds embedded in a critically Toomre-stable disk. The star-formation efficiency is in the range 1-10% per free-fall time, consistent with the notion that the pressure balance that sets the local star-formation law in the Milky Way may well be universal out to the highest star-formation intensities. AGN feedback is not necessary to regulate the star formation in the Ruby, in agreement with the absence of a bright AGN component in the infrared and radio regimes.

Testing star formation laws in a starburst galaxy at redshift 3 resolved with ALMA

“…The resulting SFR surface density we get is Σ SFR = 357 +135 −85 M yr −1 kpc −2 . These values are representative of intense star formation and are expected for the central regions of high-redshift starburst galaxies (Cibinel et al 2017;Cañameras et al 2017).…”

Full of Orions: a 200-pc mapping of the interstellar medium in the redshift-3 lensed dusty star-forming galaxy SDP.81

“…Resolved t dep measurements have been carried out for only a handful of DSFGs (see Sharon et al 2019 for a recent compilation), which generally show similarly strong (∼ 1 dex) variation in t dep . The depletion times in SDP.81 are in the extreme starburst regime, an order of magnitude lower than seen in some other high-redshift DSFGs -e. Cañameras et al (2017) found a comparably low t dep (10-100 Myr) in an extreme strongly lensed z ∼ 3 starburst PLCK G244.8+54.9, albeit at much higher star-formation surface densities (ΣSFR ∼ 2 × 10 3 M yr −1 kpc −2 ). Given the extremely short depletion time in the centre of SDP.81, sustaining the high ΣSFR requires an efficient loss of gas angular momentum to feed the star formation.…”

Planck’s Dusty GEMS

“…All GEMS have spectroscopically confirmed redshifts of z = 2.2−3.6, and apparent FIR luminosities between 5 and 27 × 10 13 µ L (Cañameras et al 2015), mainly powered by star formation and boosted by gravitational lensing from foreground clusters or massive individual galaxies by luminosityaveraged factors, µ ∼ 10−30 (Cañameras et al 2017a(Cañameras et al , 2018a. Environments probed by these galaxies range from intense, maximally star-forming clumps (Cañameras et al 2017b(Cañameras et al , 2018b to diffuse gas probed by [CII] absorption (Nesvadba et al 2016), as observed with ALMA and IRAM interferometry.…”