A PHYSICAL APPROACH TO THE IDENTIFICATION OF HIGH-<i>Z</i>MERGERS: MORPHOLOGICAL CLASSIFICATION IN THE STELLAR MASS DOMAIN

Cibinel, A.; Floc’h, E. Le; Perret, V.; Bournaud, F.; Daddi, E.; Pannella, M.; Elbaz, D.; Amram, P.; Duc, Pierre–Alain

doi:10.1088/0004-637x/805/2/181

Cited by 42 publications

(54 citation statements)

References 128 publications

(187 reference statements)

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“…The sums of the stellar mass in these maps agree within 0.1 dex with the integrated stellar-mass estimates that use longer wavelength photometry (e.g., Spitzer/IRAC 3.6-8.0 μm; Cibinel et al 2015), suggesting that the maps provide a good description of stellar-mass distribution in obscured SFGs. These stellar-mass maps serve as a reference frame to map where star formation is occurring in relation to stellar-mass buildup within each galaxy.…”

Section: Observations and Ancillary Datasupporting

confidence: 70%

VLA AND ALMA IMAGING OF INTENSE GALAXY-WIDE STAR FORMATION IN z ∼ 2 GALAXIES

Rujopakarn

Dunlop

Rieke

et al. 2016

ApJ

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137

198

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTWe present ;0 4 resolution extinction-independent distributions of star formation and dust in 11 star-forming galaxies (SFGs) at z=1.3-3.0. These galaxies are selected from sensitive blank-field surveys of the 2′×2′ Hubble Ultra-Deep Field at λ=5 cm and 1.3 mm using the Karl G. Jansky Very Large Array and Atacama Large Millimeter/submillimeter Array. They have star formation rates (SFRs), stellar masses, and dust properties representative of massive main-sequence SFGs at z∼2. Morphological classification performed on spatially resolved stellar mass maps indicates a mixture of disk and morphologically disturbed systems; half of the sample harbor X-ray active galactic nuclei (AGNs), thereby representing a diversity of z∼2 SFGs undergoing vigorous mass assembly. We find that their intense star formation most frequently occurs at the location of stellar-mass concentration and extends over an area comparable to their stellar-mass distribution, with a median diameter of 4.2±1.8 kpc. This provides direct evidence of galaxy-wide star formation in distant blank-field-selected mainsequence SFGs. The typical galactic-average SFR surface density is 2.5 M e yr −1 kpc −2 , sufficiently high to drive outflows. In X-ray-selected AGN where radio emission is enhanced over the level associated with star formation, the radio excess pinpoints the AGNs, which are found to be cospatial with star formation. The median extinctionindependent size of main-sequence SFGs is two times larger than those of bright submillimeter galaxies, whose SFRs are 3-8 times larger, providing a constraint on the characteristic SFR (∼300 M e yr −1 ) above which a significant population of more compact SFGs appears to emerge.

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Section: Observations and Ancillary Datasupporting

confidence: 70%

VLA AND ALMA IMAGING OF INTENSE GALAXY-WIDE STAR FORMATION IN z ∼ 2 GALAXIES

Rujopakarn

Dunlop

Rieke

et al. 2016

ApJ

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137

198

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“…This number needs to be adjusted for the completeness of the visual classification. We do not have exact numbers for these completenesses, however, given previous work on quantitative morphology measures (Pawlik et al 2016), it was shown that morphology measures can miss mergers identified by eye, we therefore expect the completeness to be higher than that derived by Cibinel et al (2015) (¿50-70%), leading to a correction of the upper limits by < 1.4. From the visual classification, this leads to a very conservative upper limit of 15% for clear mergers.…”

Section: Constraints On Major Merger Ratesmentioning

confidence: 95%

Host galaxies of luminousz ∼ 0.6 quasars: major mergers are not prevalent at the highest AGN luminosities

Villforth

Hamilton

Pawlik

et al. 2016

Mon. Not. R. Astron. Soc.

122

154

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Galaxy interactions are thought to be one of the main triggers of Active Galactic Nuclei (AGN), especially at high luminosities, where the accreted gas mass during the AGN lifetime is substantial. Evidence for a connection between mergers and AGN, however, remains mixed. Possible triggering mechanisms remain particularly poorly understood for luminous AGN, which are thought to require triggering by major mergers, rather than secular processes. We analyse the host galaxies of a sample of 20 optically and X-ray selected luminous AGN (log(L bol [erg/s]) > 45) at z ∼ 0.6 using HST WFC3 data in the F160W/H band. 15/20 sources have resolved host galaxies. We create a control sample of mock AGN by matching the AGN host galaxies to a control sample of non-AGN galaxies. Visual signs of disturbances are found in about 25% of sources in both the AGN hosts and control galaxies. Using both visual classification and quantitative morphology measures, we show that the levels of disturbance are not enhanced when compared to a matched control sample. We find no signs that major mergers play a dominant role in triggering AGN at high luminosities, suggesting that minor mergers and secular processes dominate AGN triggering up to the highest AGN luminosities. The upper limit on the enhanced fraction of major mergers is 20%. While major mergers might increase the incidence of (luminous AGN), they are not the prevalent triggering mechanism in the population of unobscured AGN.

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“…In that respect, it is important to calibrate with simulations that closely match the properties of the observed samples. For example, as shown in Cibinel et al (2015), the morphological signatures of mergers at z > 1 differ from those of mergers at z ∼ 0, and parametric classifications that robustly identify low-z mergers fail at z > 1.…”

Section: Introductionmentioning

confidence: 95%

Deep Learning Identifies High-z Galaxies in a Central Blue Nugget Phase in a Characteristic Mass Range

Huertas-Company

Primack

Dekel

et al. 2018

ApJ

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We use machine learning to identify in color images of high-redshift galaxies an astrophysical phenomenon predicted by cosmological simulations. This phenomenon, called the blue nugget (BN) phase, is the compact star-forming phase in the central regions of many growing galaxies that follows an earlier phase of gas compaction and is followed by a central quenching phase. We train a Convolutional Neural Network (CNN) with mock "observed" images of simulated galaxies at three phases of evolution: pre-BN, BN and post-BN, and demonstrate that the CNN successfully retrieves the three phases in other simulated galaxies. We show that BNs are identified by the CNN within a time window of ∼ 0.15 Hubble times. When the trained CNN is applied to observed galaxies from the CANDELS survey at z = 1 − 3, it successfully identifies galaxies at the three phases. We find that the observed BNs are preferentially found in galaxies at a characteristic stellar mass range, 10 9.2−10.3 M at all redshifts. This is consistent with the characteristic galaxy mass for BNs as detected in the simulations, and is meaningful because it is revealed in the observations when the direct information concerning the total Corresponding author: Marc Huertas-Company galaxy luminosity has been eliminated from the training set. This technique can be applied to the classification of other astrophysical phenomena for improved comparison of theory and observations in the era of large imaging surveys and cosmological simulations.

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A PHYSICAL APPROACH TO THE IDENTIFICATION OF HIGH-ZMERGERS: MORPHOLOGICAL CLASSIFICATION IN THE STELLAR MASS DOMAIN

Cited by 42 publications

References 128 publications

VLA AND ALMA IMAGING OF INTENSE GALAXY-WIDE STAR FORMATION IN z ∼ 2 GALAXIES

VLA AND ALMA IMAGING OF INTENSE GALAXY-WIDE STAR FORMATION IN z ∼ 2 GALAXIES

Host galaxies of luminousz ∼ 0.6 quasars: major mergers are not prevalent at the highest AGN luminosities

Deep Learning Identifies High-z Galaxies in a Central Blue Nugget Phase in a Characteristic Mass Range

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