Do Galaxy Morphologies Really Affect the Efficiency of Star Formation during the Phase of Galaxy Transition?

Abstract

Recent simulations predict that the presence of stellar bulge suppress the efficiency of star formation in early-type galaxies, and this `morphological quenching' scenario is supported by many observations. In this study, we discuss the net effect of galaxy morphologies on the star formation efficiency (SFE) during the phase of galaxy transition, on the basis of our CO($J=1-0$) observations of 28 local `green-valley' galaxies with the Nobeyama 45m Radio Telescope. We observed 13 `disk-dominated' and 15 `bulge-dominated' green-valley galaxies at fixed stellar mass ($M_{\ast }$) and star formation rate (SFR), supplemented by 1 disk- and 6 bulge-dominated galaxies satisfying the same criteria from the xCOLD~GASS survey. By using a total of 35 green-valley galaxies, we reveal that the distributions of molecular gas mass, molecular gas fraction, and SFE of green-valley galaxies do not change with their morphologies, suggesting little impact of galaxy morphologies on their SFE, and interestingly this result is also valid for normal star-forming galaxies on the SF main-sequence selected from the xCOLD~GASS galaxies. On the other hand, we find that $\sim$20 % of bulge-dominated green-valley galaxies do not show significant CO emission line, showing high SFEs for their M${}_{\ast }$ and SFR. These molecular gas deficient sources identified only in the bulge-dominated green-valley galaxies may represent an important population during the quenching phase under the influence of stellar bulge, but our results suggest that the presence of stellar bulge does not decrease the efficiency of on-going star formation, in contrast to the prediction of the morphological quenching scenario.

16 pages, 11 figures, accepted for publication in ApJ

References in corpus (15)

• Mass and environment as drivers of galaxy evolution in SDSS and zCOSMOS and the origin of the Schechter function
• Star Formation in AEGIS Field Galaxies since z=1.1 : The Dominance of Gradually Declining Star Formation, and the Main Sequence of Star-Forming Galaxies
• Combined CO & Dust Scaling Relations of Depletion Time and Molecular Gas Fractions with Cosmic Time, Specific Star Formation Rate and Stellar Mass
• xCOLD GASS: the complete IRAM-30m legacy survey of molecular gas for galaxy evolution studies
• COLD GASS, an IRAM legacy survey of molecular gas in massive galaxies: I. Relations between H2, HI, stellar content and structural properties
• GALEX-SDSS-WISE Legacy Catalog (GSWLC): Star Formation Rates, Stellar Masses and Dust Attenuations of 700,000 Low-redshift Galaxies
• COLD GASS, an IRAM Legacy Survey of Molecular Gas in Massive Galaxies: II. The non-universality of the Molecular Gas Depletion Timescale
• The UV-Optical Color Magnitude Diagram II: Physical Properties and Morphological Evolution On and Off of a Star-Forming Sequence
• Molecular and atomic gas along and across the main sequence of star-forming galaxies
• Bulge mass is king: The dominant role of the bulge in determining the fraction of passive galaxies in the Sloan Digital Sky Survey
• The impact of interactions, bars, bulges, and AGN on star formation efficiency in local massive galaxies
• The ATLAS3D Project - XXVIII. Dynamically-driven star formation suppression in early-type galaxies
• Green Valley Galaxies
• Resolved star formation and molecular gas properties of green valley galaxies: a first look with ALMA and MaNGA
• A universal correlation between star-formation activity and molecular gas properties across environments

Cited by in corpus (5)

• xGASS: The Impact of Photometric Bulges on the Scatter of HI Scaling Relations
• ALMaQUEST -- VII: Star Formation Scaling Relations of Green Valley Galaxies
• The effect of the morphological quenching mechanism on star formation activity at 0.5 < z < 1.5 in 3D-HST/CANDELS
• BreakBRD Galaxies I: Global Properties of Spiral Galaxies with Central Star Formation in Red Disks
• CO Multi-line Imaging of Nearby Galaxies (COMING). X. Physical conditions of molecular gas and the local SFR-Mass relation