scholarly journals The GALEX Arecibo SDSS Survey – VIII. Final data release. The effect of group environment on the gas content of massive galaxies

2013 ◽  
Vol 436 (1) ◽  
pp. 34-70 ◽  
Author(s):  
Barbara Catinella ◽  
David Schiminovich ◽  
Luca Cortese ◽  
Silvia Fabello ◽  
Cameron B. Hummels ◽  
...  
2019 ◽  
Vol 487 (2) ◽  
pp. 2061-2069 ◽  
Author(s):  
Tao Hong ◽  
Lister Staveley-Smith ◽  
Karen L Masters ◽  
Christopher M Springob ◽  
Lucas M Macri ◽  
...  

2018 ◽  
Vol 621 ◽  
pp. A13 ◽  
Author(s):  
Jovan Veljanoski ◽  
Amina Helmi ◽  
Maarten Breddels ◽  
Lorenzo Posti

Context. Extended stellar haloes are a natural by-product of the hierarchical formation of massive galaxies like the Milky Way. If merging is a non-negligible factor in the growth of our Galaxy, evidence of such events should be encoded in its stellar halo. The reliable identification of genuine halo stars is a challenging task, however. Aims. With the advent of the Gaia space telescope, we are ushered into a new era of Galactic astronomy. The first Gaia data release contains the positions, parallaxes, and proper motions for over two million stars, mostly in the solar neighbourhood. The second Gaia data release will enlarge this sample to over 1.5 billion stars, the brightest ~ 5 million of which will have full phase-space information. Our aim for this paper is to develop a machine learning model for reliably identifying halo stars, even when their full phase-space information is not available. Methods. We use the Gradient Boosted Trees algorithm to build a supervised halo star classifier. The classifier is trained on a sample of stars extracted from the Gaia Universe Model Snapshot, which is also convolved with the errors of the public TGAS data, which is a subset of Gaia DR1, as well as with the expected uncertainties for the upcoming Gaia DR2 catalogue. We also trained our classifier on a dataset resulting from the cross-match between the TGAS and RAVE catalogues, where the halo stars are labelled in an entirely model-independent way. We then use this model to identify halo stars in TGAS. Results. When full phase-space information is available and for Gaia DR2-like uncertainties, our classifier is able to recover 90% of the halo stars with at most 30% distance errors, in a completely unseen test set and with negligible levels of contamination. When line-of-sight velocity is not available, we recover ~ 60% of such halo stars, with less than 10% contamination. When applied to the TGAS catalogue, our classifier detects 337 high confidence red giant branch halo stars. At first glance this number may seem small, however, it is consistent with the expectation from the models, given the uncertainties in the data. The large parallax errors are in fact the biggest limitation in our ability to identify a large number of halo stars in all the cases studied.


2016 ◽  
Vol 456 (4) ◽  
pp. 4156-4173 ◽  
Author(s):  
Francisco-Shu Kitaura ◽  
Sergio Rodríguez-Torres ◽  
Chia-Hsun Chuang ◽  
Cheng Zhao ◽  
Francisco Prada ◽  
...  
Keyword(s):  

2014 ◽  
Vol 447 (1) ◽  
pp. 234-245 ◽  
Author(s):  
Martin White ◽  
Beth Reid ◽  
Chia-Hsun Chuang ◽  
Jeremy L. Tinker ◽  
Cameron K. McBride ◽  
...  

2010 ◽  
Vol 6 (S277) ◽  
pp. 47-54
Author(s):  
Françoise Combes

AbstractI review some recent results about the molecular content of galaxies, obtained essentially from the CO lines, but also dense tracers, or the dust continuum emission. New results have been obtained on molecular cloud physics, and their efficiency to form stars, shedding light on the Kennicutt-Schmidt law as a function of surface density and galaxy type. Large progress has been made on galaxy at moderate and high redshifts, allowing to interprete the star formation history and star formation efficiency as a function of gas content, or galaxy evolution. In massive galaxies, the gas fraction was higher in the past, and galaxy disks were more unstable and more turbulent. ALMA observations will allow the study of more normal galaxies at high z with higher spatial resolution and sensitivity.


2019 ◽  
Vol 15 (S352) ◽  
pp. 281-281
Author(s):  
Allison Man

AbstractA key outstanding issue in galaxy evolution studies is how galaxies quench their star formation. I will present new results from our VLT/X-Shooter, ALMA and VLA campaign of a pilot sample of lensed quiescent massive galaxies at z > 1.5. Lensing magnification enables us to spatially resolve the stellar structure and kinematics of these compact galaxies, that are otherwise barely resolvable even with HST. Our deep X-Shooter spectra provided multiple absorption lines enabling strong constraints on their stellar populations, namely their star formation rates, ages, dispersions, and in some cases metallicities. Our complementary ALMA+VLA programme probes their molecular gas content through CO emission. All these observations provide unparalleled constraints on their quenching mechanisms. Our results indicate that quiescent galaxies at z ∼ 2 (1) have short star formation timescales of a few hundred Myrs; (2) have a variety of stellar morphology from exponential disks to bulges; (3) are devoid of molecular gas; and (4) host low-luminosity active galactic nuclei which may be responsible for suppressing star formation. In addition to discussing the insights gained on quenching, I will highlight how these findings bring about new questions that can be addressed with future JWST and ALMA studies.


2020 ◽  
Vol 499 (1) ◽  
pp. 210-229 ◽  
Author(s):  
Richard Neveux ◽  
Etienne Burtin ◽  
Arnaud de Mattia ◽  
Alex Smith ◽  
Ashley J Ross ◽  
...  

ABSTRACT We measure the clustering of quasars of the final data release (DR16) of eBOSS. The sample contains $343\, 708$ quasars between redshifts 0.8 ≤ z ≤ 2.2 over $4699\, \mathrm{deg}^2$. We calculate the Legendre multipoles (0,2,4) of the anisotropic power spectrum and perform a BAO and a Full-Shape (FS) analysis at the effective redshift zeff = 1.480. The errors include systematic errors that amount to 1/3 of the statistical error. The systematic errors comprise a modelling part studied using a blind N-body mock challenge and observational effects studied with approximate mocks to account for various types of redshift smearing and fibre collisions. For the BAO analysis, we measure the transverse comoving distance DM(zeff)/rdrag = 30.60 ± 0.90 and the Hubble distance DH(zeff)/rdrag = 13.34 ± 0.60. This agrees with the configuration space analysis, and the consensus yields: DM(zeff)/rdrag = 30.69 ± 0.80 and DH(zeff)/rdrag = 13.26 ± 0.55. In the FS analysis, we fit the power spectrum using a model based on Regularised Perturbation Theory, which includes redshift space distortions and the Alcock–Paczynski effect. The results are DM(zeff)/rdrag = 30.68 ± 0.90 and DH(zeff)/rdrag = 13.52 ± 0.51 and we constrain the linear growth rate of structure f(zeff)σ8(zeff) = 0.476 ± 0.047. Our results agree with the configuration space analysis. The consensus analysis of the eBOSS quasar sample yields: DM(zeff)/rdrag = 30.21 ± 0.79, DH(zeff)/rdrag = 3.23 ± 0.47, and f(zeff)σ8(zeff) = 0.462 ± 0.045 and is consistent with a flat ΛCDM cosmological model using Planck results.


2020 ◽  
Author(s):  
I Schroder ◽  
P de Caritat ◽  
L Wallace ◽  
J Trihey ◽  
C Boreham ◽  
...  

2015 ◽  
Vol 11 (S317) ◽  
pp. 182-189
Author(s):  
Jenny E. Greene ◽  
Chung-Pei Ma ◽  
Andrew Goulding ◽  
Nicholas J. McConnell ◽  
John P. Blakeslee ◽  
...  

AbstractWe discuss the stellar halos of massive elliptical galaxies, as revealed by our ambitious integral-field spectroscopic survey MASSIVE. We show that metallicity drops smoothly as a function of radius out to ~ 2.5 Re, while the [α/Fe] abundance ratios stay flat. The stars in the outskirts likely formed rapidly (to explain the high ratio of alpha to Fe) but in a relatively shallow potential (to explain the low metallicities). This is consistent with expectations for a two-phase growth of massive galaxies, in which the second phase involves accretion of small satellites. We also show some preliminary study of the gas content of these most MASSIVE galaxies.


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