A contribution of star-forming clumps and accreting satellites to the mass assembly of z similar to 2 galaxies

TY - JOUR

T1 - A contribution of star-forming clumps and accreting satellites to the mass assembly of z similar to 2 galaxies

AU - Zanella, A.

AU - Le Floc'h, E.

AU - Harrison, C. M.

AU - Daddi, E.

AU - Bernhard, E.

AU - Gobat, R.

AU - Strazzullo, V

AU - Valentino, F.

AU - Cibinel, A.

AU - Sanchez Almeida, J.

AU - Kohandel, M.

AU - Fensch, J.

AU - Behrendt, M.

AU - Burkert, A.

AU - Onodera, M.

AU - Bournaud, F.

AU - Scholtz, J.

PY - 2019/10/21

Y1 - 2019/10/21

N2 - We investigate the contribution of clumps and satellites to the galaxy mass assembly. We analysed spatially resolved Hubble Space Telescope observations (imaging and slitless spectroscopy) of 53 star-forming galaxies at z ∼ 1-3. We created continuum and emission line maps and pinpointed residual 'blobs' detected after subtracting the galaxy disc. Those were separated into compact (unresolved) and extended (resolved) components. Extended components have sizes ∼2 kpc and comparable stellar mass and age as the galaxy discs, whereas the compact components are 1.5 dex less massive and 0.4 dex younger than the discs. Furthermore, the extended blobs are typically found at larger distances from the galaxy barycentre than the compact ones. Prompted by these observations and by the comparison with simulations, we suggest that compact blobs are in situ formed clumps, whereas the extended ones are accreting satellites. Clumps and satellites enclose, respectively, ∼20 per cent and 80 per cent of the galaxy stellar mass, ∼30 per cent and ∼20 per cent of its star formation rate. Considering the compact blobs, we statistically estimated that massive clumps (Mθ ≳ 109 Mθ) have lifetimes of ∼650 Myr, and the less massive ones (108 < Mθ < 109 Mθ) of ∼145 Myr. This supports simulations predicting long-lived clumps (lifetime ≳100 Myr). Finally, ≲30 per cent (13 per cent) of our sample galaxies are undergoing single (multiple) merger(s), they have a projected separation≲10 kpc, and the typical mass ratio of our satellites is 1:5 (but ranges between 1:10 and 1:1), in agreement with literature results for close pair galaxies.

AB - We investigate the contribution of clumps and satellites to the galaxy mass assembly. We analysed spatially resolved Hubble Space Telescope observations (imaging and slitless spectroscopy) of 53 star-forming galaxies at z ∼ 1-3. We created continuum and emission line maps and pinpointed residual 'blobs' detected after subtracting the galaxy disc. Those were separated into compact (unresolved) and extended (resolved) components. Extended components have sizes ∼2 kpc and comparable stellar mass and age as the galaxy discs, whereas the compact components are 1.5 dex less massive and 0.4 dex younger than the discs. Furthermore, the extended blobs are typically found at larger distances from the galaxy barycentre than the compact ones. Prompted by these observations and by the comparison with simulations, we suggest that compact blobs are in situ formed clumps, whereas the extended ones are accreting satellites. Clumps and satellites enclose, respectively, ∼20 per cent and 80 per cent of the galaxy stellar mass, ∼30 per cent and ∼20 per cent of its star formation rate. Considering the compact blobs, we statistically estimated that massive clumps (Mθ ≳ 109 Mθ) have lifetimes of ∼650 Myr, and the less massive ones (108 < Mθ < 109 Mθ) of ∼145 Myr. This supports simulations predicting long-lived clumps (lifetime ≳100 Myr). Finally, ≲30 per cent (13 per cent) of our sample galaxies are undergoing single (multiple) merger(s), they have a projected separation≲10 kpc, and the typical mass ratio of our satellites is 1:5 (but ranges between 1:10 and 1:1), in agreement with literature results for close pair galaxies.

KW - galaxies: evolution

KW - galaxies: interactions

KW - galaxies: irregular

KW - galaxies: ISM

KW - galaxies: star formation

KW - galaxies: structure

U2 - 10.1093/mnras/stz2099

DO - 10.1093/mnras/stz2099

M3 - Journal article

SN - 0035-8711

VL - 489

SP - 2792

EP - 2818

JO - Royal Astronomical Society. Monthly Notices

JF - Royal Astronomical Society. Monthly Notices

IS - 2

ER -