Scaling relations of star-forming regions: from kpc-sized clumps to H ii regions

Abstract

We present the properties of eight star‐forming regions, or ‘clumps,’ in three galaxies at z∼ 1.3 from the WiggleZ Dark Energy Survey, which are resolved with the OH Suppressing InfraRed Imaging Spectrograph (OSIRIS) integral field spectrograph. Within turbulent discs, σ∼ 90 km s−1, clumps are measured with average sizes of 1.5 kpc and average Jeans masses of 4.2 × 109 M⊙, in total accounting for 40–60 per cent of the stellar mass of the discs. These findings lend observational support to models that predict larger clumps will form as a result of higher disc velocity dispersions driven‐up by cosmological gas accretion. As a consequence of the changes in global environment, it may be predicted that star‐forming regions at high redshift should not resemble star‐forming regions locally. Yet despite the increased sizes and dispersions, clumps and H ii regions are found to follow tight scaling relations over the range z= 0–2 for Hα size, velocity dispersion, luminosity and mass when comparing >2000 H ii regions locally and 30 clumps at z > 1 (σ∝r0.42 ± 0.03, LHα∝r2.72 ± 0.04, LHα∝σ4.18 ± 0.21 and ). We discuss these results in the context of the existing simulations of clump formation and evolution, with an emphasis on the processes that drive‐up the turbulent motions in the interstellar medium. Our results indicate that while the turbulence of discs may have important implications for the size and luminosity of regions which form within them, the same processes govern their formation from high redshift to the current epoch.

Star formation sustained by gas accretion

“…Tadpoles are only a particular sub-set within the BCD family. The abundance of the BCD high-z counterparts, the clumpy-disk galaxies, also increases with increasing z (Elmegreen et al 2005;Swinbank et al 2009;Genzel et al 2011;Wisnioski et al 2012). Therefore, the arguments used for tadpoles supporting gas accretion can be extended to BCDs as well.…”

The Dawes Review 1: Kinematic Studies of Star-Forming Galaxies Across Cosmic Time

“…They again find that around half the objects have disc-like kinematics and high intrinsic velocity dispersions and clumpyness. The resolved star-formation properties and clump scaling relations were examined further in Wisnioski et al (2012). An interesting difference between the Wright et al and Wisnioski et.…”

“…Often this is done by simple peak-finding codes, visual inspection, or validation (Swinbank et al 2009;Genzel et al 2011;Wisnioski et al 2012;Guo et al 2012) as the number of individual clumps per galaxy is typically ß2-5. Of course the problem of identifying compact blobs against a background is a long studied one in astronomy and there has been considerable borrowing of well-established algorithms.…”

Galaxy And Mass Assembly (GAMA): $\mathcal {M_\star }\text{--}R_{\rm e}$ relations ofz= 0 bulges, discs and spheroids

“…Bruce et al 2012;Buitrago et al 2013;Mortlock et al 2013). Galaxies at high redshifts are typically more irregular with thick slab-like disc structures and clumpy star-forming regions (Wisnioski et al 2012). In addition, they can be very compact but massive.…”