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ABSTRACT We present an analysis of the galaxy stellar mass function (SMF) of 14 known protoclusters between 2.0 < z < 2.5 in the COSMOS field, down to a mass limit of 109.5 M⊙. We use existing photometric redshifts with a statistical background subtraction, and consider star-forming and quiescent galaxies identified from (NUV − r) and (r − J) colours separately. Our fiducial sample includes galaxies within 1 Mpc of the cluster centres. The shape of the protocluster SMF of star-forming galaxies is indistinguishable from that of the general field at this redshift. Quiescent galaxies, however, show a flatter SMF than in the field, with an upturn at low mass, though this is only significant at ∼2σ. There is no strong evidence for a dominant population of quiescent galaxies at any mass, with a fraction <15 per cent at 1σ confidence for galaxies with log M*/M⊙ < 10.5. We compare our results with a sample of galaxy groups at 1 < z < 1.5, and demonstrate that a significant amount of environmental quenching must take place between these epochs, increasing the relative abundance of high-mass ($$\rm M_{\ast } \gt 10^{10.5} {\rm M}_{\odot }$$) quiescent galaxies by a factor ≳ 2. However, we find that at lower masses ($$\rm M_{\ast } \lt 10^{10.5} {\rm M}_{\odot }$$), no additional environmental quenching is required.
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A SAMI and MaNGA view on the stellar kinematics of galaxies on the star-forming main sequence
ABSTRACT Galaxy internal structure growth has long been accused of inhibiting star formation in disc galaxies. We investigate the potential physical connection between the growth of dispersion-supported stellar structures (e.g. classical bulges) and the position of galaxies on the star-forming main sequence at z ∼ 0. Combining the might of the SAMI and MaNGA galaxy surveys, we measure the λRe spin parameter for 3289 galaxies over $$9.5 \lt \log M_{\star } [\rm {M}_{\odot }] \lt 12$$. At all stellar masses, galaxies at the locus of the main sequence possess λRe values indicative of intrinsically flattened discs. However, above $$\log M_{\star }[\rm {M}_{\odot }]\sim 10.5$$ where the main sequence starts bending, we find tantalizing evidence for an increase in the number of galaxies with dispersion-supported structures, perhaps suggesting a connection between bulges and the bending of the main sequence. Moving above the main sequence, we see no evidence of any change in the typical spin parameter in galaxies once gravitationally interacting systems are excluded from the sample. Similarly, up to 1 dex below the main sequence, λRe remains roughly constant and only at very high stellar masses ($$\log M_{\star }[\rm {M}_{\odot }]\gt 11$$), do we see a rapid decrease in λRe once galaxies decline in star formation activity. If this trend is confirmed, it would be indicative of different quenching mechanisms acting on high- and low-mass galaxies. The results suggest that whilst a population of galaxies possessing some dispersion-supported structure is already present on the star-forming main sequence, further growth would be required after the galaxy has quenched to match the kinematic properties observed in passive galaxies at z ∼ 0.
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- Award ID(s):
- 2009416
- PAR ID:
- 10265907
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 503
- Issue:
- 4
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- 4992 to 5005
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/mnras/stab573
