We study the formation and evolution of a sample of Lyman Break Galaxies in the Epoch of Reionization by using high-resolution ($sim 10 , m pc$), cosmological zoom-in simulations part of the SERRA suite. In SERRA, we follow the interstellar medium (ISM) thermo-chemical non-equilibrium evolution, and perform on-the-fly radiative transfer of the interstellar radiation field (ISRF). The simulation outputs are post-processed to compute the emission of far infrared lines ([CII], [NII], and [OIII]). At $z=8$, the most massive galaxy, `Freesia', has an age $t_star simeq 409, m Myr$, stellar mass $M_star simeq 4.2 imes 10^9 m M_odot$, and a star formation rate $ m SFR simeq 11.5, m M_odot m yr^-1$, due to a recent burst. Freesia has two stellar components (A and B) separated by $simeq 2.5, m kpc$; other 11 galaxies are found within $56.9 pm 21.6 , m kpc$. The mean ISRF in the Habing band is $G = 7.9, G_0$ and is spatially uniform; in contrast, the ionisation parameter is $U = 2^+20_-2 imes 10^-3$, and has a patchy distribution peaked at the location of star-forming sites. The resulting ionising escape fraction from Freesia is $f_ m escsimeq 2%$. While [CII] emission is extended (radius 1.54 kpc), [OIII] is concentrated in Freesia-A (0.85 kpc), where the ratio $Sigma_ m [OIII]/Sigma_ m [CII] simeq 10$. As many high-$z$ galaxies, Freesia lies below the local [CII]-SFR relation. We show that this is the general consequence of a starburst phase (pushing the galaxy above the Kennicutt-Schmidt relation) which disrupts/photodissociates the emitting molecular clouds around star-forming sites. Metallicity has a sub-dominant impact on the amplitude of [CII]-SFR deviations.
Deep into the structure of the first galaxies: SERRA views
Pallottini, A;Ferrara, A;Decataldo, D;Gallerani, S;Vallini, L;Carniani, S;Behrens, C;KOHANDEL, Mahsa;Salvadori, S
2019
Abstract
We study the formation and evolution of a sample of Lyman Break Galaxies in the Epoch of Reionization by using high-resolution ($sim 10 , m pc$), cosmological zoom-in simulations part of the SERRA suite. In SERRA, we follow the interstellar medium (ISM) thermo-chemical non-equilibrium evolution, and perform on-the-fly radiative transfer of the interstellar radiation field (ISRF). The simulation outputs are post-processed to compute the emission of far infrared lines ([CII], [NII], and [OIII]). At $z=8$, the most massive galaxy, `Freesia', has an age $t_star simeq 409, m Myr$, stellar mass $M_star simeq 4.2 imes 10^9 m M_odot$, and a star formation rate $ m SFR simeq 11.5, m M_odot m yr^-1$, due to a recent burst. Freesia has two stellar components (A and B) separated by $simeq 2.5, m kpc$; other 11 galaxies are found within $56.9 pm 21.6 , m kpc$. The mean ISRF in the Habing band is $G = 7.9, G_0$ and is spatially uniform; in contrast, the ionisation parameter is $U = 2^+20_-2 imes 10^-3$, and has a patchy distribution peaked at the location of star-forming sites. The resulting ionising escape fraction from Freesia is $f_ m escsimeq 2%$. While [CII] emission is extended (radius 1.54 kpc), [OIII] is concentrated in Freesia-A (0.85 kpc), where the ratio $Sigma_ m [OIII]/Sigma_ m [CII] simeq 10$. As many high-$z$ galaxies, Freesia lies below the local [CII]-SFR relation. We show that this is the general consequence of a starburst phase (pushing the galaxy above the Kennicutt-Schmidt relation) which disrupts/photodissociates the emitting molecular clouds around star-forming sites. Metallicity has a sub-dominant impact on the amplitude of [CII]-SFR deviations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
