scholarly journals Overview of the Near-IR S0 Galaxy Survey (NIRS0S)

2011 ◽  
Vol 2011 ◽  
pp. 1-17 ◽  
Author(s):  
E. Laurikainen ◽  
H. Salo ◽  
R. Buta ◽  
J. H. Knapen
Keyword(s):  
Surface Brightness ◽  
Limited Sample ◽  
Scale Parameters ◽  
Hubble Sequence ◽  
Near Ir ◽  
Galaxy Sample ◽  
Nearby Galaxies ◽  
The Masses ◽  
First Time ◽  
Similar Image Quality

An overview of the results of the near-IR S0 galaxy survey (NIRS0S) is presented. NIRS0S is a magnitude- (mB⩽12.5 mag) and inclination- (<65∘) limited sample of ̃200 nearby galaxies, mainly S0s, but includes also Sa and E galaxies. It uses deepKs-band images, typically reaching a surface brightness of 23.5 mag arcsec−2. Detailed visual and photometric classifications were made, for the first time coding also the lenses in a systematic manner. As a comparison sample, a similar sized spiral galaxy sample with similar image quality was used. Based on our analysis, the Hubble sequence was revisited: following the early idea by van den Bergh we suggested that the S0s are spread throughout the Hubble sequence in parallel tuning forks as spirals (S0a, S0b, S0c, etc.). This is evidenced by our improved bulge-to-total (B/T) flux ratios in the S0s, reaching small values typical to late-type spirals. The properties of bulges and disks in S0s were found to be similar to those in spirals and, also, the masses and scale parameters of the bulges and disks to be coupled. It was estimated that the spiral bulges brighter than −20 mag inK-band are massive enough to be converted into the bulges of S0s merely by star formation. Bars were found to be fairly robust both in S0s and spirals, but, inspite of that, bars might evolve significantly within the Hubble sequence.

scholarly journals B/T-ratios in the Hubble sequence

2006 ◽  
Vol 2 (S235) ◽  
pp. 36-38
Author(s):  
Eija Laurikainen ◽  
H. Salo ◽  
R. Buta ◽  
J. H. Knapen ◽  
T. Speltincx ◽  
...  
Keyword(s):  
Shape Parameter ◽  
Flux Ratio ◽  
Early Type ◽  
Evolutionary Processes ◽  
Hubble Sequence ◽  
Near Ir ◽  
Nearby Galaxies

AbstractWe discuss bulges in the Hubble sequence, based on the analysis of deep near-IR images for a sample of 216 nearby galaxies. Using a 2D multicomponent decomposition code, we find that the average bulge-to-total (B/T) flux ratio is less than 0.25 across all morphological types. Even 50% of the early-type galaxies (S0-S0/a) are found to have nuclear bars, inner disks or nuclear rings inside the bulge. Also, the shape parameter of the bulge is on average ≤2 for all Hubble types. Our results are consistent with the picture in which bulges even in many early-type galaxies were formed by secular evolutionary processes. We find two galaxies that might be stripped spirals, belonging to the so far empty S0c morphological class introduced by van den Bergh (1979).

Surface Brightness Scale of Galactic Cepheids

1999 ◽  
Vol 190 ◽  
pp. 561-562
Author(s):  
G. P. Di Benedetto
Keyword(s):  
Surface Brightness ◽  
Variable Stars ◽  
Giant Stars ◽  
Near Ir

An accurate calibration of the surface brightness scaleSVas a function of the near-IR color (V–K) has been recently measured for non-variable Galactic dwarf and giant stars. It can be shown that this correlation can be applied to theSVscale of Galactic Cepheid variable stars, which are of major cosmological interest.

scholarly journals A study of stellar orbit fractions: simulated IllustrisTNG galaxies compared to CALIFA observations

2019 ◽  
Vol 489 (1) ◽  
pp. 842-854 ◽  
Author(s):  
Dandan Xu ◽  
Ling Zhu ◽  
Robert Grand ◽  
Volker Springel ◽  
Shude Mao ◽  
...  
Keyword(s):  
Observational Data ◽  
Mass Range ◽  
Stellar Mass ◽  
Model Uncertainties ◽  
Massive Galaxies ◽  
Hubble Sequence ◽  
Galaxy Sample ◽  
The Mean ◽  
Stellar Orbit

ABSTRACT Motivated by the recently discovered kinematic ‘Hubble sequence’ shown by the stellar orbit-circularity distribution of 260 CALIFA galaxies, we make use of a comparable galaxy sample at z = 0 with a stellar mass range of $M_{*}/\mathrm{M}_{\odot }\in [10^{9.7},\, 10^{11.4}]$ selected from the IllustrisTNG simulation and study their stellar orbit compositions in relation to a number of other fundamental galaxy properties. We find that the TNG100 simulation broadly reproduces the observed fractions of different orbital components and their stellar mass dependences. In particular, the mean mass dependences of the luminosity fractions for the kinematically warm and hot orbits are well reproduced within model uncertainties of the observed galaxies. The simulation also largely reproduces the observed peak and trough features at $M_{*}\approx 1\rm {-}2\times 10^{10}\, \mathrm{M}_{\odot }$ in the mean distributions of the cold- and hot-orbit fractions, respectively, indicating fewer cooler orbits and more hotter orbits in both more- and less-massive galaxies beyond such a mass range. Several marginal disagreements are seen between the simulation and observations: the average cold-orbit (counter-rotating) fractions of the simulated galaxies below (above) $M_{*}\approx 6\times 10^{10}\, \mathrm{M}_{\odot }$ are systematically higher than the observational data by $\lesssim 10{{\ \rm per\ cent}}$ (absolute orbital fraction); the simulation also seems to produce more scatter for the cold-orbit fraction and less so for the non-cold orbits at any given galaxy mass. Possible causes that stem from the adopted heating mechanisms are discussed.

The Biggest Ears in the Sky: LIGO

2020 ◽  
pp. 108-136
Author(s):  
John W. Moffat
Keyword(s):  
Black Holes ◽  
Gravitational Waves ◽  
Nobel Prize ◽  
Executive Director ◽  
Numerical Relativity ◽  
Washington State ◽  
Wave Form ◽  
Press Conference ◽  
The Masses ◽  
First Time

At a press conference on February 11, 2016, David Reitz, LIGO Executive Director, announced, “We did it!” They detected gravitational waves for the first time. Both LIGO sites, in Washington state and Louisiana, registered the incoming gravitational waves from two black holes colliding and merging far away. Over the following months, more mergers were detected. Gravitational waves are caused by the acceleration of a massive object, which stretches and compresses spacetime in a wave-like motion that is incredibly small and difficult to detect. Numerical relativity research over decades has produced over a quarter of a million template solutions of Einstein’s equations. The best template fit to the wave form data identifies the masses and spins of the two merging black holes. Much of this chapter describes the technology of the LIGO apparatus. On October 3, 2017, Barish, Thorne, and Weiss, the founders of LIGO, received the Nobel Prize for Physics.

scholarly journals SNe from Surveys and Patrols

1994 ◽  
Vol 161 ◽  
pp. 37-41
Author(s):  
C. Pollas
Keyword(s):  
Wide Field ◽  
Good Tool ◽  
Sn 1987A ◽  
Knowing That ◽  
Transient Source ◽  
Total Magnitude ◽  
History Of ◽  
Nearby Galaxies ◽  
First Time ◽  
Parent Galaxy

The name of Zwicky is attached to the first photographic Palomar Survey and to the History of SNe study. An exciting study resumed by the striking image (M = −19) of a transient source appearing at extragalactic distance, as bright as the total magnitude of its parent galaxy. Expected to explode once a century, such an event is rare. But the more galaxies are checked the more SNe are found. That is why the wide-field is a good tool. The Palomar team SNe activity was followed by a quiet period of the whole SNe discovery (Fig. 1); from those the Cero El Robles search emerged in the early eighties. Several important patrols continued with Schmidt telescopes of size about 0.5 m (Bern, Hungary, Urss…) in spite of the low level of SNe found. Important because knowing that no SN exploded in a galaxy (especially in the sample of nearby galaxies) is the basis of the statistics. The SNe production increased in the late eighties. At the same time, the closest modern SN (1987A) led for the first time to the use of a number of instruments complementing each other to increase our understanding of SNe. But more important than the production of new SNe, is the increase of their spectroscopic classification which is necessary to the SNe work.

scholarly journals Wobbly discs – corrugations seen in the dust lanes of edge-on galaxies

2020 ◽  
Vol 495 (4) ◽  
pp. 3705-3714
Author(s):  
Chaitra A Narayan ◽  
Ralf-Jürgen Dettmar ◽  
Kanak Saha
Keyword(s):  
Stability Analysis ◽  
Small Scale ◽  
Host Galaxies ◽  
Lower Mass ◽  
Limited Sample ◽  
Unsharp Masking ◽  
Bending Waves ◽  
First Time ◽  
Larger Sample ◽  
Disc Galaxies

ABSTRACT We report the detection of small-scale bending waves, also known as corrugations, in the dust lanes of five nearby edge-on disc galaxies. This phenomenon, where the disc mid-plane bends to become wavy, just as in warps but on a smaller scale, is seen here for the first time, in the dust lanes running across the discs. Because they are seen in absorption, this feature must be present in the dust disc in the outskirts of these galaxies. We enhance the visibility of these features using unsharp masking, trace the dust mid-plane across the disc, measure the corrugation amplitude by eye and the corrugation wavelength using Fourier analysis. The corrugation amplitude is found to be in the range of 70–300pc and the wavelengths lie between 1 and 5 kpc. In this limited sample, we find that the amplitude of the corrugations tends to be larger for lower mass galaxies, whereas the wavelength of corrugation does not seem to depend on the mass of host galaxies. Linear stability analysis is performed to find out the dynamical state of these dust discs. Based on WKB analysis, we find that the dust corrugations in about half of our sample are stable. Further analysis, on a larger sample would be useful to strengthen the above results.

scholarly journals Probing the Redshift Desert Using the Gemini Deep Deep Survey: Observing Galaxy Mass Assembly at z > 1

2005 ◽  
Vol 216 ◽  
pp. 390-397
Author(s):  
Karl Glazebrook ◽  
Keyword(s):  
Spectroscopic Studies ◽  
Star Forming ◽  
Hubble Sequence ◽  
First Results ◽  
Deep Survey ◽  
Redshift Survey ◽  
Mass Assembly ◽  
Galaxy Assembly ◽  
First Time ◽  
The Universe

The aim of the Gemini Deep Deep Survey is to push spectroscopic studies of complete galaxy samples (both red and blue objects) significantly beyond z = 1; this is the redshift where the current Hubble sequence of ellipticals and spirals is already extant. In the Universe at z = 2 the only currently spectroscopically confirmed galaxies are blue, star-forming and of fragmented morphology. Exploring this transition means filling the ‘redshift desert’ 1 < z < 2 where there is a dearth of spectroscopic measurements. To do this we need to secure redshifts of the oldest, reddest galaxies (candidate ellipticals) beyond z > 1 which has led us to carry out the longest exposure redshift survey ever done: 100 ksec spectroscopic MOS exposures with GMOS on Gemini North. We have developed an implementation of the CCD “nod & shuffle” technique to ensure precise sky-subtraction in these ultra-deep exposures. At the halfway mark the GDDS now has ∼ 36 galaxies in the redshift desert 1.2 < z < 2 extending up to z = 1.97 and I < 24.5 with secure redshifts based on weak rest-frame UV absorption features complete for both red, old objects and young, blue objects. The peak epoch of galaxy assembly is now being probed by direct spectroscopic investigation for the first time. on behalf of the GDDS team I present our first results on the properties of galaxies in the ‘redshift desert’.

scholarly journals The identification of dust heating mechanisms in nearby galaxies using Herschel 160/250 and 250/350 μm surface brightness ratios

2015 ◽  
Vol 448 (1) ◽  
pp. 135-167 ◽  
Author(s):  
G. J. Bendo ◽  
M. Baes ◽  
S. Bianchi ◽  
M. Boquien ◽  
A. Boselli ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Nearby Galaxies

The Parkes 21 cm Multibeam Receiver

1996 ◽  
Vol 13 (3) ◽  
pp. 243-248 ◽  
Author(s):  
L. Staveley-Smith ◽  
W. E. Wilson ◽  
T. S. Bird ◽  
M. J. Disney ◽  
R. D. Ekers ◽  
...  
Keyword(s):  
Data Acquisition ◽  
Focal Plane ◽  
Surface Brightness ◽  
Focal Plane Array ◽  
Optical Surface ◽  
Velocity Range ◽  
Large Area ◽  
Optical Extinction ◽  
Technical Aspects ◽  
Nearby Galaxies

Several extragalactic HI surveys using a λ21 cm 13-beam focal plane array will begin in early 1997 using the Parkes 64 m telescope. These surveys are designed to detect efficiently nearby galaxies that have failed to be identified optically because of low optical surface brightness or high optical extinction. We discuss scientific and technical aspects of the multibeam receiver, including astronomical objectives, feed, receiver and correlator design and data acquisition. A comparison with other telescopes shows that the Parkes multibeam receiver has significant speed advantages for any large-area λ21 cm galaxy survey in the velocity range range 0–14000 km s−1.

scholarly journals Be it therefore resolved: cosmological simulations of dwarf galaxies with 30 solar mass resolution

2019 ◽  
Vol 490 (3) ◽  
pp. 4447-4463 ◽  
Author(s):  
Coral Wheeler ◽  
Philip F Hopkins ◽  
Andrew B Pace ◽  
Shea Garrison-Kimmel ◽  
Michael Boylan-Kolchin ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Stellar Rotation ◽  
Solar Mass ◽  
Dynamical Mass ◽  
Low Mass ◽  
Star Formation Histories ◽  
First Time

ABSTRACT We study a suite of extremely high-resolution cosmological Feedback in Realistic Environments simulations of dwarf galaxies ($M_{\rm halo} \lesssim 10^{10}\rm \, M_{\odot }$), run to z = 0 with $30\, \mathrm{M}_{\odot }$ resolution, sufficient (for the first time) to resolve the internal structure of individual supernovae remnants within the cooling radius. Every halo with $M_{\rm halo} \gtrsim 10^{8.6}\, \mathrm{M}_{\odot }$ is populated by a resolved stellar galaxy, suggesting very low-mass dwarfs may be ubiquitous in the field. Our ultra-faint dwarfs (UFDs; $M_{\ast }\lt 10^{5}\, \mathrm{M}_{\odot }$) have their star formation (SF) truncated early (z ≳ 2), likely by reionization, while classical dwarfs ($M_{\ast }\gt 10^{5}\, \mathrm{M}_{\odot }$) continue forming stars to z &lt; 0.5. The systems have bursty star formation histories, forming most of their stars in periods of elevated SF strongly clustered in both space and time. This allows our dwarf with M*/Mhalo &gt; 10−4 to form a dark matter core ${\gt}200\rm \, pc$, while lower mass UFDs exhibit cusps down to ${\lesssim}100\rm \, pc$, as expected from energetic arguments. Our dwarfs with $M_{\ast }\gt 10^{4}\, \mathrm{M}_{\odot }$ have half-mass radii (R1/2) in agreement with Local Group (LG) dwarfs (dynamical mass versus R1/2 and stellar rotation also resemble observations). The lowest mass UFDs are below surface brightness limits of current surveys but are potentially visible in next-generation surveys (e.g. LSST). The stellar metallicities are lower than in LG dwarfs; this may reflect pre-enrichment of the LG by the massive hosts or Pop-III stars. Consistency with lower resolution studies implies that our simulations are numerically robust (for a given physical model).

Sign in / Sign up

Export Citation Format

Share Document