Multiobject Spectroscopy of Young Star Clusters in NGC 4676

Chien, Li-Hsin; Barnes, Joshua E.; Kewley, Lisa J.; Chambers, K.

doi:10.1086/518215

Cited by 36 publications

(44 citation statements)

References 23 publications

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“…These authors suggest that a merger event (which already took place in this galaxy several Gyrs ago) could increase the metallicities in the outskirts of this galaxy. However, some authors have found that star-forming regions located in tidal tails display super solar and solar oxygen abundances and flat metallicity distributions (Chien et al 2007 andTorres-Flores et al 2014, respectively). Chien et al (2007) argued that the flat distributions may suggest gas mixing within the tail.…”

Section: Discussionmentioning

confidence: 99%

“…These authors found ages in the range of ∼4-20 Myrs. The young ages for our star-forming regions suggest that these regions were formed in situ (Chien et al 2007, de Mello et al 2008. In order to determine the colour excess of each starforming region in NGC 6845, we have used the starburst extinction law, defined by Calzetti et al (2000), using Au=E(B-V)×6.08, Ag=E(B-V)×4.737, Ar=E(B-V)×3.54, respectively.…”

Section: Ages and Internal Extinctions Of The Star-forming Regionsmentioning

confidence: 99%

“…Following the N2 index proposed by Marino et al (2013) Chien et al (2007) for the northern tidal tail of the merging galaxy pair NGC 4676. These authors found values for the oxygen metallicity in the range 12+log(O/H)= 8.86-8.97, but they used the R23 method.…”

Section: Oxygen Abundances and Metallicity Gradientsmentioning

confidence: 99%

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NGC 6845: metallicity gradients and star formation in a complex compact group

Olave-Rojas

Torres-Flores

Carrasco

et al. 2015

Mon. Not. R. Astron. Soc.

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We have obtained Gemini/GMOS spectra of 28 regions located across the interacting group NGC 6845, spanning from the inner regions of the four major galaxies (NGC 6845A, B, C, D) to the tidal tails of NGC 6845A. All regions in the tails are starforming objects with ages younger than 10 Myr. We derived the gas-phase metallicity gradients across NGC 6845A and its two tails and we find that these are shallower than those for isolated galaxies. NGC 6845A has a gas-phase oxygen central metallicity of 12+log(O/H)∼8.5 and a flat gas-phase metallicity gradient (β=0.002±0.004 dex kpc −1 ) out to ∼4 × R 25 (to the end of the longest tidal tail). Considering the mass-metallicity relation, the central region of NGC 6845A displays a lower oxygen abundance than the expected for its mass. Taking into account this fact and considering the flat oxygen distribution measured along the eastern tidal tail, we suggest that an interaction event has produced a dilution in the central metallicity of this galaxy and the observed flattening in its metal distribution. We found that the star formation process along the eastern tidal structure has not been efficient enough to increase the oxygen abundances in this place, suggesting that this structure was formed from enriched material.

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Section: Discussionmentioning

confidence: 99%

Section: Ages and Internal Extinctions Of The Star-forming Regionsmentioning

confidence: 99%

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NGC 6845: metallicity gradients and star formation in a complex compact group

Olave-Rojas

Torres-Flores

Carrasco

et al. 2015

Mon. Not. R. Astron. Soc.

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“…They are a classic example of a major gas-rich prograde merger, where the roughly equal mass of the progenitors and coincidence of the sense of rotation and orbital motion lead to lengthy tidal tails. NGC 4676A and B (hereafter referred to as the Mice) are one of the earliest stage gas-rich major mergers visible in the nearby Universe, observed close to their apocentre, with N-body simulations and observations agreeing that first passage must have occurred around 170 Myr ago (Barnes 2004;Chien et al 2007). The system is an outlying member of the Coma cluster, located about 4 • or 1.7 virial radii from the centre (Kubo et al 2007), with a velocity about 350 km s −1 from the mean cluster velocity (Burbidge & Burbidge 1961).…”

Section: Introductionmentioning

confidence: 97%

The Mice at play in the CALIFA survey

Wild

Rosales-Ortega

Falcón-Barroso

et al. 2014

A&A

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We present optical integral field spectroscopy (IFS) observations of the Mice, a major merger between two massive ( 10 11 M ) gas-rich spirals NGC 4676A and B, observed between first passage and final coalescence. The spectra provide stellar and gas kinematics, ionised gas properties, and stellar population diagnostics, over the full optical extent of both galaxies with ∼1.6 kpc spatial resolution. The Mice galaxies provide a perfect case study that highlights the importance of IFS data for improving our understanding of local galaxies. The impact of first passage on the kinematics of the stars and gas has been significant, with strong bars most likely induced in both galaxies. The barred spiral NGC 4676B exhibits a strong twist in both its stellar and ionised gas disk. The edge-on disk galaxy NGC 4676A appears to be bulge free, with a strong bar causing its "boxy" light profile. On the other hand, the impact of the merger on the stellar populations has been minimal thus far. By combining the IFS data with archival multiwavelength observations we show that star formation induced by the recent close passage has not contributed significantly to the total star formation rate or stellar mass of the galaxies. Both galaxies show bicones of high ionisation gas extending along their minor axes. In NGC 4676A the high gas velocity dispersion and Seyfert-like line ratios at large scaleheight indicate a powerful outflow. Fast shocks (v s ∼ 350 km s −1 ) extend to ∼6.6 kpc above the disk plane. The measured ram pressure (P/k = 4.8 × 10 6 K cm −3 ) and mass outflow rate (∼8−20 M yr −1 ) are similar to superwinds from local ultra-luminous infrared galaxies, although NGC 4676A only has a moderate infrared luminosity of 3 × 10 10 L . Energy beyond what is provided by the mechanical energy of the starburst appears to be required to drive the outflow. Finally, we compare the observations to mock kinematic and stellar population maps extracted from a hydrodynamical merger simulation. The models show little enhancement in star formation during and following first passage, in agreement with the observations. We highlight areas where IFS data could help further constrain the models.

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“…Numbers of studies in all wavebands have characterised the properties of interacting systems, in particular their star formation activity, with the aim of pinning down the underlying physical processes (e.g. Schombert et al 1990;Hibbard & Mihos 1995;Bournaud et al 2004;Chien et al 2007;Smith et al 2010;Boquien et al 2011;Saintonge et al 2012;Scudder et al 2012). …”

Section: Introductionmentioning

confidence: 99%

Star formation triggered by galaxy interactions in modified gravity

Famaey¹,

Kroupa²

2016

Mon. Not. R. Astron. Soc.

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Together with interstellar turbulence, gravitation is one key player in star formation. It acts both at galactic scales in the assembly of gas into dense clouds, and inside those structures for their collapse and the formation of pre-stellar cores. To understand to what extent the large scale dynamics govern the star formation activity of galaxies, we present hydrodynamical simulations in which we generalise the behaviour of gravity to make it differ from Newtonian dynamics in the low acceleration regime. We focus on the extreme cases of interacting galaxies, and compare the evolution of galaxy pairs in the dark matter paradigm to that in the Milgromian Dynamics (MOND) framework. Following up on the seminal work by Tiret & Combes, this paper documents the first simulations of galaxy encounters in MOND with a detailed Eulerian hydrodynamical treatment of baryonic physics, including star formation and stellar feedback. We show that similar morphologies of the interacting systems can be produced by both the dark matter and MOND formalisms, but require a much slower orbital velocity in the MOND case. Furthermore, we find that the star formation activity and history are significantly more extended in space and time in MOND interactions, in particular in the tidal debris. Such differences could be used as observational diagnostics and make interacting galaxies prime objects in the study of the nature of gravitation at galactic scales.

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Multiobject Spectroscopy of Young Star Clusters in NGC 4676

Cited by 36 publications

References 23 publications

NGC 6845: metallicity gradients and star formation in a complex compact group

NGC 6845: metallicity gradients and star formation in a complex compact group

The Mice at play in the CALIFA survey

Star formation triggered by galaxy interactions in modified gravity

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