The Main Sequence at $z sim 1.3$ contains a sizable fraction of galaxies with compact star formation sizes: a new population of early post-starbursts?. (arXiv:1905.02958v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Puglisi_A/0/1/0/all/0/1">A. Puglisi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Daddi_E/0/1/0/all/0/1">E. Daddi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_D/0/1/0/all/0/1">D. Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bournaud_F/0/1/0/all/0/1">F. Bournaud</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Silverman_J/0/1/0/all/0/1">J. D. Silverman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Circosta_C/0/1/0/all/0/1">C. Circosta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Calabro_A/0/1/0/all/0/1">A. Calabrò</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aravena_M/0/1/0/all/0/1">M. Aravena</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cibinel_A/0/1/0/all/0/1">A. Cibinel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dannerbauer_H/0/1/0/all/0/1">H. Dannerbauer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Delvecchio_I/0/1/0/all/0/1">I. Delvecchio</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Elbaz_D/0/1/0/all/0/1">D. Elbaz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gao_Y/0/1/0/all/0/1">Y. Gao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gobat_R/0/1/0/all/0/1">R. Gobat</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jin_S/0/1/0/all/0/1">S. Jin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Floch_E/0/1/0/all/0/1">E. Le Floc'h</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Magdis_G/0/1/0/all/0/1">G. E. Magdis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mancini_C/0/1/0/all/0/1">C. Mancini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Riechers_D/0/1/0/all/0/1">D. A. Riechers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rodighiero_G/0/1/0/all/0/1">G. Rodighiero</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sargent_M/0/1/0/all/0/1">M. Sargent</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Valentino_F/0/1/0/all/0/1">F. Valentino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zanisi_L/0/1/0/all/0/1">L. Zanisi</a>
ALMA measurements for 93 $Herschel$-selected galaxies at $1.1 leqslant z
leqslant 1.7$ in COSMOS reveal a sizable ($>29$%) population with compact
star formation (SF) sizes, lying on average $> times 3.6$ below the optical
stellar mass ($M_{star}$)-size relation of disks. This sample widely spans the
star-forming Main Sequence (MS), having $10^{8} leqslant M_{star} leqslant
10^{11.5} M_{odot}$ and $20 leqslant SFR leqslant 680 M_{odot} rm
yr^{-1}$. The 32 size measurements and 61 upper limits are measured on ALMA
images that combine observations of CO(5-4), CO(4-3), CO(2-1) and $lambda_{rm
obs} sim 1.1-1.3 rm mm$ continuum, all tracing the star-forming molecular
gas. These compact galaxies have instead normally extended $K_{band}$ sizes,
suggesting strong specific $SFR$ gradients. Compact galaxies comprise the
$50pm18 %$ of MS galaxies at $M_{star} > 10^{11} M_{odot}$. This is not
expected in standard bi-modal scenarios where MS galaxies are mostly
steadily-growing extended disks. We suggest that compact MS objects are early
post-starburst galaxies in which the merger-driven boost of SF has subsided.
They retain their compact SF size until either further gas accretion restores
pre-merger galaxy-wide SF, or until becoming quenched. The fraction of
merger-affected SF inside the MS seems thus larger than anticipated and might
reach $sim 50$% at the highest $M_{star}$. The presence of large galaxies
above the MS demonstrates an overall poor correlation between galaxy SF size
and specific $SFR$.
ALMA measurements for 93 $Herschel$-selected galaxies at $1.1 leqslant z
leqslant 1.7$ in COSMOS reveal a sizable ($>29$%) population with compact
star formation (SF) sizes, lying on average $> times 3.6$ below the optical
stellar mass ($M_{star}$)-size relation of disks. This sample widely spans the
star-forming Main Sequence (MS), having $10^{8} leqslant M_{star} leqslant
10^{11.5} M_{odot}$ and $20 leqslant SFR leqslant 680 M_{odot} rm
yr^{-1}$. The 32 size measurements and 61 upper limits are measured on ALMA
images that combine observations of CO(5-4), CO(4-3), CO(2-1) and $lambda_{rm
obs} sim 1.1-1.3 rm mm$ continuum, all tracing the star-forming molecular
gas. These compact galaxies have instead normally extended $K_{band}$ sizes,
suggesting strong specific $SFR$ gradients. Compact galaxies comprise the
$50pm18 %$ of MS galaxies at $M_{star} > 10^{11} M_{odot}$. This is not
expected in standard bi-modal scenarios where MS galaxies are mostly
steadily-growing extended disks. We suggest that compact MS objects are early
post-starburst galaxies in which the merger-driven boost of SF has subsided.
They retain their compact SF size until either further gas accretion restores
pre-merger galaxy-wide SF, or until becoming quenched. The fraction of
merger-affected SF inside the MS seems thus larger than anticipated and might
reach $sim 50$% at the highest $M_{star}$. The presence of large galaxies
above the MS demonstrates an overall poor correlation between galaxy SF size
and specific $SFR$.
http://arxiv.org/icons/sfx.gif
