Galaxy And Mass Assembly (GAMA): blue spheroids within 87 Mpc

Mahajan, Smriti; Drinkwater, Michael J.; Driver, Simon P.; Hopkins, A. M.; Graham, Alister W.; Brough, Sarah; Brown, M. J. I.; Holwerda, Benne W.; Owers, Matt S.; Pimbblet, Kevin A.

doi:10.1093/mnras/stx3202

Cited by 30 publications

(24 citation statements)

References 37 publications

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“…ilar sSFRs to dwarf irregular galaxies, it seems likely that the LBSs have sufficient fuel to maintain substantial star formation for several more Gyr. Indeed, though we do not as yet have gas masses for our LBS sample, Mahajan et al (2018) do find that their blue spheroids (including many of our lowest redshift LBSs) display similar gas properties to star-forming disk galaxies. If these LBSs were to decrease or end their star formation, we would expect them to move towards the region of the colour vs. stellar mass diagrams occupied by low-mass Es (see Fig.…”

Section: Discussionmentioning

confidence: 69%

Star-forming, rotating spheroidal galaxies in the GAMA and SAMI surveys

Moffett

Phillipps

Robotham

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The Galaxy And Mass Assembly (GAMA) survey has morphologically identified a class of "Little Blue Spheroid" (LBS) galaxies whose relationship to other classes of galaxies we now examine in detail. Considering a sample of 868 LBSs, we find that such galaxies display similar but not identical colours, specific star formation rates, stellar population ages, mass-to-light ratios, and metallicities to Sd-Irr galaxies. We also find that LBSs typically occupy environments of even lower density than those of Sd-Irr galaxies, where ∼65% of LBS galaxies live in isolation. Using deep, highresolution imaging from VST KiDS and the new Bayesian, two-dimensional galaxy profile modeling code PROFIT, we further examine the detailed structure of LBSs and find that their Sérsic indices, sizes, and axial ratios are compatible with those of low-mass elliptical galaxies. We then examine SAMI Galaxy survey integral field emission line kinematics for a subset of 62 LBSs and find that the majority (42) of these galaxies display ordered rotation with the remainder displaying disturbed/non-ordered dynamics. Finally, we consider potential evolutionary scenarios for a population with this unusual combination of properties, concluding that LBSs are likely formed by a mixture of merger and accretion processes still recently active in low-redshift dwarf populations. We also infer that if LBS-like galaxies were subjected to quenching in a rich environment, they would plausibly resemble cluster dwarf ellipticals.

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Section: Discussionmentioning

confidence: 69%

Star-forming, rotating spheroidal galaxies in the GAMA and SAMI surveys

Moffett

Phillipps

Robotham

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…The remaining population of red spirals seems to be a product of environmental effects which lead to loss of gas and dust, and eventually low SFR. Observations supporting the impact of such environmental mechanisms on the transformation of galaxies in intermediate-density environments of galaxy groups (Rasmussen et al 2012) and large-scale filaments (Mahajan, Raychaudhury, & Pimbblet 2012;Mahajan et al 2018) have been discussed in the literature. In particular, the results of Rasmussen et al (2012) favour a quenching timescale of 2 Gyr, which is in broad agreement with the suggested scenario for the creation of passively-evolving spirals by other studies (Wolf et al 2009;Koyama et al 2011;Schawinski et al 2014), and the transition time of passive disc galaxies through the green valley (Cortese & Hughes 2009;Bremer et al 2018).…”

Section: Discussionmentioning

confidence: 98%

“…But at z ∼ 0 it is linearly correlated with the instantaneous measure of SFR obtained from the Hα emission line (see fig. 1 of Mahajan et al 2018).…”

Section: Physical Propertiesmentioning

confidence: 98%

Galaxy And Mass Assembly (GAMA): properties and evolution of red spiral galaxies

Mahajan

Gupta

Rana

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We use multi-wavelength data from the Galaxy and Mass Assembly (GAMA) survey to explore the cause of red optical colours in nearby (0.002 < z < 0.06) spiral galaxies. We show that the colours of red spiral galaxies are a direct consequence of some environmentrelated mechanism(s) which has removed dust and gas, leading to a lower star formation rate. We conclude that this process acts on long timescales (several Gyr) due to a lack of morphological transformation associated with the transition in optical colour. The sSFR and dust-to-stellar mass ratio of red spiral galaxies is found to be statistically lower than blue spiral galaxies. On the other hand, red spirals are on average 0.9 dex more massive, and reside in environments 2.6 times denser than their blue counterparts. We find no evidence of excessive nuclear activity, or higher inclination angles to support these as the major causes for the red optical colours seen in 47% of all spirals in our sample. Furthermore, for a small subsample of our spiral galaxies which are detected in HI, we find that the SFR of gas-rich red spiral galaxies is lower by ∼ 1 dex than their blue counterparts.

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“…Second, the r ′ -band magnitude may not be proper to represent the shape sample of highredshift galaxies. The r ′ -band magnitude is known as a good proxy of the stellar mass (Mahajan et al 2018;Du et al 2020), but it corresponds to λ ∼ 2000-3000 Å at z ∼ 1.3, which is below the 4000 Å break. We only expect weak spectral energy density, regardless of the actual stellar mass, and hence r ′ -band magnitudes may not represent the stellar and total mass.…”

Section: Ia Of Red Galaxies As a Function Of Redshiftmentioning

confidence: 99%

First Evidence of Intrinsic Alignments of Red Galaxies at $z > 1$: Cross-correlation between CFHTLenS and FastSound Samples

Tonegawa,

Okumura

2021

Preprint

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We report the first evidence of intrinsic alignment (IA) of red galaxies at z > 1. We measure the gravitational shear-intrinsic ellipticity (GI) cross-correlation function at z ∼ 1.3 using galaxy positions from the FastSound spectroscopic survey and galaxy shapes from Canada-Hawaii-France telescope lensing survey data. Adopting the non-linear alignment model, we obtain a 2.4σ level detection of the IA amplitude, A LA = 27.48 +11.53 −11.54 , larger than the value extrapolated from the constraints obtained at lower redshifts. Our measured IA is translated into a ∼ 20% contamination to the weak lensing power spectrum for the red galaxies. This marginal detection of IA for red galaxies at z > 1 motivates the continuing investigation of the nature of IA for weak lensing studies. Furthermore, our result provides the first step to utilize IA measurements in future high-z surveys as a cosmological probe, complementary to galaxy clustering and lensing.

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Galaxy And Mass Assembly (GAMA): blue spheroids within 87 Mpc

Cited by 30 publications

References 37 publications

Star-forming, rotating spheroidal galaxies in the GAMA and SAMI surveys

Star-forming, rotating spheroidal galaxies in the GAMA and SAMI surveys

Galaxy And Mass Assembly (GAMA): properties and evolution of red spiral galaxies

First Evidence of Intrinsic Alignments of Red Galaxies at $z > 1$: Cross-correlation between CFHTLenS and FastSound Samples

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