Astronomy

How is stellar mass of a galaxy obtained?

How is stellar mass of a galaxy obtained?


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I believe there is a difference between the mass calculated using the orbital speed and the stellar mass of the galaxy. So how is the stellar mass calculated?

Thank you :)


In short, you count stars. Of course you can't count or even see all the stars, so you have to count certain types of (bright) stars and then assume that the ratio of these to all the stars in their neighbourhood is similar to the ratio in a local part of the Galaxy where we can do a more complete census.

Once we have an idea of a number for the stars in any region, we can use an assumed mass distribution for the stars to calculate the total stellar mass.

There are details and nuances (e.g. the form of the stellar mass distribution depends on the age of the population), but that's the basic process in our own Galaxy.

In other galaxies, where you don't resolve individual stars, you work on the basis of mass to luminosity ratios for typical populations to convert a luminosity to a stellar mass.


Mind the Gap: Scientists Use Stellar Mass to Link Exoplanets to Planet-Forming Disks

Using data for more than 500 young stars observed with the Atacama Large Millimeter/submillimeter Array (ALMA), scientists have uncovered a direct link between protoplanetary disk structures—the planet-forming disks that surround stars—and planet demographics. The survey proves that higher mass stars are more likely to be surrounded by disks with “gaps” in them and that these gaps directly correlate to the high occurrence of observed giant exoplanets around such stars. These results provide scientists with a window back through time, allowing them to predict what exoplanetary systems looked like through each stage of their formation.

“We found a strong correlation between gaps in protoplanetary disks and stellar mass, which can be linked to the presence of large, gaseous exoplanets,” said Nienke van der Marel, a Banting fellow in the Department of Physics and Astronomy at the University of Victoria in British Columbia, and the primary author on the research. “Higher mass stars have relatively more disks with gaps than lower mass stars, consistent with the already known correlations in exoplanets, where higher mass stars more often host gas-giant exoplanets. These correlations directly tell us that gaps in planet-forming disks are most likely caused by giant planets of Neptune mass and above.”

Gaps in protoplanetary disks have long been considered as overall evidence of planet formation. However, there has been some skepticism due to the observed orbital distance between exoplanets and their stars. “One of the primary reasons that scientists have been skeptical about the link between gaps and planets before is that exoplanets at wide orbits of tens of astronomical units are rare. However, exoplanets at smaller orbits, between one and ten astronomical units, are much more common,” said Gijs Mulders, assistant professor of astronomy at Universidad Adolfo Ibáñez in Santiago, Chile, and co-author on the research. “We believe that planets that clear the gaps will migrate inwards later on.”

The new study is the first to show that the number of gapped disks in these regions matches the number of giant exoplanets in a star system. “Previous studies indicated that there were many more gapped disks than detected giant exoplanets,” said Mulders. “Our study shows that there are enough exoplanets to explain the observed frequency of the gapped disks at different stellar masses.”

The correlation also applies to star systems with low-mass stars, where scientists are more likely to find massive rocky exoplanets, also known as Super-Earths. Van der Marel, who will become an assistant professor at Leiden University in the Netherlands beginning September 2021 said, “Lower mass stars have more rocky Super-Earths—between an Earth mass and a Neptune mass. Disks without gaps, which are more compact, lead to the formation of Super-Earths.”

This link between stellar mass and planetary demographics could help scientists identify which stars to target in the search for rocky planets throughout the Milky Way. “This new understanding of stellar mass dependencies will help to guide the search for small, rocky planets like Earth in the solar neighborhood,” said Mulders, who is also a part of the NASA-funded Alien Earths team. “We can use the stellar mass to connect the planet-forming disks around young stars to exoplanets around mature stars. When an exoplanet is detected, the planet-forming material is usually gone. So the stellar mass is a ‘tag’ that tells us what the planet-forming environment might have looked like for these exoplanets.”

And what it all comes down to is dust. “An important element of planet formation is the influence of dust evolution,” said van der Marel. “Without giant planets, dust will always drift inwards, creating the optimal conditions for the formation of smaller, rocky planets close to the star.”

The current research was conducted using data for more than 500 objects observed in prior studies using ALMA’s high-resolution Band 6 and Band 7 antennas. At present, ALMA is the only telescope that can image the distribution of millimeter-dust at high enough angular resolution to resolve the dust disks and reveal its substructure, or lack thereof. “Over the past five years, ALMA has produced many snapshot surveys of nearby star-forming regions resulting in hundreds of measurements of disk dust mass, size, and morphology,” said van der Marel. “The large number of observed disk properties has allowed us to make a statistical comparison of protoplanetary disks to the thousands of discovered exoplanets. This is the first time that a stellar mass dependency of gapped disks and compact disks has been successfully demonstrated using the ALMA telescope.”

“Our new findings link the beautiful gap structures in disks observed with ALMA directly to the properties of the thousands of exoplanets detected by the NASA Kepler mission and other exoplanet surveys,” said Mulders. “Exoplanets and their formation help us place the origins of the Earth and the Solar System in the context of what we see happening around other stars.”


The Faintest Dwarf Galaxies

Joshua D. Simon
Vol. 57, 2019

Abstract

The lowest luminosity ( L) Milky Way satellite galaxies represent the extreme lower limit of the galaxy luminosity function. These ultra-faint dwarfs are the oldest, most dark matter–dominated, most metal-poor, and least chemically evolved stellar systems . Read More

Supplemental Materials

Figure 1: Census of Milky Way satellite galaxies as a function of time. The objects shown here include all spectroscopically confirmed dwarf galaxies as well as those suspected to be dwarfs based on l.

Figure 2: Distribution of Milky Way satellites in absolute magnitude () and half-light radius. Confirmed dwarf galaxies are displayed as dark blue filled circles, and objects suspected to be dwarf gal.

Figure 3: Line-of-sight velocity dispersions of ultra-faint Milky Way satellites as a function of absolute magnitude. Measurements and uncertainties are shown as blue points with error bars, and 90% c.

Figure 4: (a) Dynamical masses of ultra-faint Milky Way satellites as a function of luminosity. (b) Mass-to-light ratios within the half-light radius for ultra-faint Milky Way satellites as a function.

Figure 5: Mean stellar metallicities of Milky Way satellites as a function of absolute magnitude. Confirmed dwarf galaxies are displayed as dark blue filled circles, and objects suspected to be dwarf .

Figure 6: Metallicity distribution function of stars in ultra-faint dwarfs. References for the metallicities shown here are listed in Supplemental Table 1. We note that these data are quite heterogene.

Figure 7: Chemical abundance patterns of stars in UFDs. Shown here are (a) [C/Fe], (b) [Mg/Fe], and (c) [Ba/Fe] ratios as functions of metallicity, respectively. UFD stars are plotted as colored diamo.

Figure 8: Detectability of faint stellar systems as functions of distance, absolute magnitude, and survey depth. The red curve shows the brightness of the 20th brightest star in an object as a functi.

Figure 9: (a) Color–magnitude diagram of Segue 1 (photometry from Muñoz et al. 2018). The shaded blue and pink magnitude regions indicate the approximate depth that can be reached with existing medium.


Gamma rays from the Galactic Centre region: A review

Christopher van Eldik , in Astroparticle Physics , 2015

2.4 The Galactic supermassive black hole and its immediate vicinity

Since its discovery in 1974 [3] , the bright and ultra-compact radio source Sgr A * , located at the dynamical centre of the Galaxy, is in the focus of GC research. Today, a wealth of precise astronomical observations support the idea that Sgr A * is a supermassive BH. Since it is known that the dynamics of (active) galactic nuclei are largely driven by the presence of BHs in their cores, the GC offers the unique possibility to study in close view processes that are presumably at work in a large class of extragalactic nuclei as well (with the caveat that the energy output of the latter is much larger).

Key to establish the BH nature of Sgr A * are observations with modern telescopes providing intrinsic resolution up to sub-milli-arcseconds. One of the most impressive studies is based on near IR observations of the orbits of young stars in the direct (as close as 0.1′′ in projection) vicinity of Sgr A * , from which the mass of the central compact object, M A * ∼ 4 × 10 6 M ⊙ , can be inferred with great accuracy [17,18,44,45] . At the same time, these studies show that the stars’ orbits are consistent with a purely Keplarian motion around a point mass centred on the Sgr A * radio position. These findings are supported by VLBA measurements [46] , which put strong limits on the motion of the radio position of Sgr A * itself with respect to the barycentre of the Galaxy as determined from stellar orbits . The results imply that the object responsible for the radio emission must be rather massive, and a lower limit of 4 × 10 5 M on the mass of the Sgr A * radio source is inferred from the measurements [46] . At a wavelength of 7 mm, VLBI observations have resolved the size of the radio emission region to 24 ± 2 Schwarzschild radii [47] . Combining these findings, there is not much doubt that Sgr A * can only be a supermassive BH (see, e.g., the reviews [48,49] for more information).

The photon flux from the direction of Sgr A * has been measured across a large range of energies. The energy spectrum in the millimetre to IR domain is characterised by a hard power-law with photon index ∼0.3, a turn-over at about 1 GHz, followed by a cutoff at about 10 3 GHz [50] , explained as synchrotron radiation of relativistic electrons (e.g. [51,52] ).

While being relatively bright at radio frequencies, Sgr A * is only a faint X-ray emitter [53] , but shows bright outbursts on time scales of a few minutes to several hours [54–57] . Assuming a black hole mass exceeding some 10 6 solar masses and invoking causality arguments, these short flare durations limit the size of the emission region to be less than 10 BH Schwarzschild radii. Non-thermal processes near the event horizon might produce relativistic electrons and thus explain the X-ray short-time variability (e.g. [58–60] ). To a certain extent, flares in the NIR band are predicted by these models, and such flares have been observed [61] . Observations in the hard X-ray/soft γ-ray band by the INTEGRAL instrument, on the contrary, show a faint, but steady emission from the direction of the GC [62] .

At even higher energies, identification of any γ-ray emission with radio or X-ray counterparts is hampered by the comparatively modest angular resolution of HE γ-ray telescopes. Observations with the EGRET instrument onboard the Compton Gamma-Ray Observatory in the late 1990s yielded a strong excess (named 3EG J1746-2851) of >30 MeV γ-rays on top of the expected Galactic diffuse emission [63] . Within an error circle of 0.2°, the centroid of this excess is compatible with the position of Sgr A * . However, the energy output of 3EG J1746 in the MeV–GeV range (∼10 37 erg s − 1 ) exceeds by at least an order of magnitude the energy released close to Sgr A * at any other wavelength. In any case, due to the relatively poor angular resolution of EGRET, source confusion hampers the interpretation of the signal especially at low energies, where the EGRET point spread function is poorest. Furthermore, diffuse emission from the Galactic ridge is a dominating component at these energies, causing unavoidable systematic uncertainties in the position determination. A follow-up analysis of the position of 3EG J1746, using only events with energies >1 GeV to improve the instrument point spread function (PSF), disfavours an association of the source with Sgr A * at the 99.9% CL [64] . New data taken with the Fermi-LAT instrument, however, significantly improve on these findings (see below).

Currently, Sgr A * is in a rather low state of emission, since its bolometric luminosity is smaller than 10 − 8 L Edd (with the Eddington luminosity being L Edd ∼ 10 44 erg s − 1 for a BH with Sgr A * ’s mass). It is suggested that the BH is currently accreting only a moderate amount of gas from the winds of massive young stars populating the inner ∼1 pc region [65] . This does not exclude that the GC was much more active in the past: indeed, there is evidence of recent (∼100 years ago) activity deduced from the presence of X-ray reflection nebulae [66–68] in nearby molecular clouds, and even of times of much longer activity during the last 10 7 years, as suggested by the presence of giant outflows from the GC region (e.g. [69] ).


Stellar stream of galaxy NGC 5907 has a morphology different than previously thought

Dragonfly imaging of the NGC 5907 field, with North up and East to the left. Credit: van Dokkum et al., 2019.

Using Dragonfly Telephoto Array, astronomers have revisited the spiral galaxy NGC 5907 and provided more insights into the morphology of its stellar stream. The new observations indicate that this feature has a qualitatively different morphology than when it was observed about a decade ago. The new findings are reported in a paper published June 26 on arXiv.org.

Stellar streams are remnants of dwarf galaxies or globular clusters that once orbited a galaxy but have been disrupted and stretched out along their orbits by tidal forces of their hosts. So far, more than 40 stellar streams have been identified in the Milky Way, just a few in the Andromeda galaxy, and about 10 outside the Local Group.

For astronomers, stellar stream could provide important information on the frequency of the accretion of small objects onto larger ones. Given that their morphologies reflect their orbits, they could serve as probes of the gravitational potential. Moreover, they could be also used as a tool to constrain the mass and structure of dark matter halos.

One of the bes-known stellar streams outside the Milky Way galaxy is the one associated with NGC 5907, a spiral galaxy located some 55.4 million light years away, with a stellar mass of around 80 billion solar masses. The stream was detected in 1998 when sections of a loop around the disk of NGC 5907 were identified. Further observations of this feature, conducted 10 years later, showed that the stream exhibits not one but two complete loops, enveloping the galaxy in a giant corkscrew-like structure.

Now, new observations performed by a group of astronomers led by Pieter van Dokkum of Yale University, delivered more detailed images of NGC 5907's stellar stream. The new data, collected by the Dragonfly Telephoto Array, indicate that the morphology of this feature is different than that in the study published a decade ago.

"Here, we report on new low-surface-brightness imaging of NGC 5907 over a wide field as part of an imaging campaign of nearby galaxies with the Dragonfly Telephoto Array," the astronomers wrote in the paper.

In general, the study found that NGC 5907 is a relatively straightforward system composed of the remnant of a progenitor galaxy, a leading tail and a long, faint trailing tail. The astronomers said that the stellar stream of this galaxy is similar to the Sagittarius stream around the Milky Way in terms of its spatial extent and stellar mass.

However, the most puzzling aspect of the study is that it has not confirmed the presence of the second loop in NGC 5907's stellar stream. The researchers noted that the leading tail in the image obtained by the Dragonfly Telephoto Array falls in between the two loops identified in the observations conducted in 2008.

Furthermore, by comparing the new images with these acquired ten years ago the extent of the Western stream was found to be greater. Additionally, the stream was found to have more substructure and brightness variations, and the ratio of the apparent width of the stream to the apparent width of the disk of the galaxy turned out to be much smaller.

Trying to find a possible explanation of such discrepancies in the data, the authors of the study point out to the image processing procedures that were applied to the data as the images collected in 2008 were processed by an amateur astronomer.

"Amateurs have played an important role in this field as they convincingly demonstrated the power of small telescopes for low surface brightness imaging. However, the methods that are used by the amateur community typically do not allow for quantitative analysis, as their image processing is generally optimized for aesthetic qualities rather than preserving the linearity and noise properties of the data," the researchers concluded.


UKnowledge

Context. The form and evolution of the galaxy stellar mass function (GSMF) at high redshifts provide crucial information on star formation history and mass assembly in the young Universe, close or even prior to the epoch of reionization.

Aims. We used the unique combination of deep optical/near-infrared/mid-infrared imaging provided by HST, Spitzer, and the VLT in the CANDELS-UDS, GOODS-South, and HUDF fields to determine the GSMF over the redshift range 3.5 ≤ z ≤ 7.5.

Methods. We used the HST WFC3/IR near-infrared imaging from CANDELS and HUDF09, reaching H ≃ 27 − 28.5 over a total area of 369 arcmin 2 , in combination with associated deep HST ACS optical data, deep Spitzer IRAC imaging from the SEDS programme, and deep Y and K-band VLT Hawk-I images from the HUGS programme, to select a galaxy sample with high-quality photometric redshifts. These have been calibrated with more than 150 spectroscopic redshifts in the range 3.5 ≤ z ≤ 7.5, resulting in an overall precision of σz/ (1 + z)

0.037. With this database we have determined the low-mass end of the high-redshift GSMF with unprecedented precision, reaching down to masses as low as M

Results. We find that the GSMF at 3.5 ≤ z ≤ 7.5 depends only slightly on the recipes adopted to measure the stellar masses, namely the photometric redshifts, the star formation histories, the nebular contribution, or the presence of AGN in the parent sample. The low-mass end of the GSMF is steeper than has been found at lower redshifts, but appears to be unchanged over the redshift range probed here. Meanwhile the high-mass end of the GSMF appears to evolve primarily in density, although there is also some evidence of evolution in characteristic mass. Our results are very different from previous mass function estimates based on converting UV galaxy luminosity functions into mass functions via tight mass-to-light relations. Integrating our evolving GSMF over mass, we find that the growth of stellar mass density is barely consistent with the time-integral of the star formation rate density over cosmic time at z> 4.

Conclusions. These results confirm the unique synergy of the CANDELS+HUDF, HUGS, and SEDS surveys for the discovery and study of moderate/low-mass galaxies at high redshifts, and reaffirm the importance of space-based infrared selection for the unbiased measurement of the evolving GSMF in the young Universe.


Abstract

Using observations from the FourStar Galaxy Evolution Survey (ZFOURGE), we obtain the deepest measurements to date of the galaxy stellar mass function (SMF) at 0.2 < z < 3. ZFOURGE provides well-constrained photometric redshifts made possible through deep medium-bandwidth imaging at 1-2 μm. We combine this with Hubble Space Telescope imaging from the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey, allowing for the efficient selection of both blue and red galaxies down to stellar masses of 10 9.5 M at z 2.5. The total surveyed area is 316 arcmin 2 distributed over three independent fields. We supplement these data with the wider and shallower NEWFIRM Medium-Band Survey to provide stronger constraints at high masses. Several studies at z ≤ 1.5 have revealed a steepening of the slope at the low-mass end of the SMF, leading to an upturn at masses <10 10 M that is not well described by a standard single-Schechter function. We find evidence that this feature extends to at least z 2 and that it can be found in both the star-forming and quiescent populations individually. The characteristic mass (M*) and slope at the lowest masses (α) of a double-Schechter function fit to the SMF stay roughly constant at Log(M/M 10.65 and -1.5, respectively. The SMF of star-forming galaxies has evolved primarily in normalization, while the change in shape is relatively minor. Our data allow us, for the first time, to observe a rapid buildup at the low-mass end of the quiescent SMF. Since z = 2.5, the total stellar mass density of quiescent galaxies (down to 10 9 M has increased by a factor of 12, whereas the mass density of star-forming galaxies only increases by a factor of 2.2.


Research Box Title

In two separate studies using NASA’s upcoming James Webb Space Telescope, a team of astronomers will observe dwarf galaxy companions to the Milky Way and the nearby Andromeda galaxy. Studying these small companions will help scientists learn about galaxy formation and the properties of dark matter, a mysterious substance thought to account for approximately 85% of the matter in the universe.

In the first study, the team will gain knowledge of dark matter by measuring the motions of stars in two dwarf companions to the Milky Way. In the second study, they will examine the motions of four dwarf galaxies around our nearest large galactic neighbor, the Andromeda galaxy. This will help determine if some of Andromeda’s satellite galaxies orbit inside a flat plane, like the planets around our Sun. If they do, that would have important implications for understanding galaxy formation. The principal investigator for both programs is Roeland van der Marel of the Space Telescope Science Institute (STScI) in Baltimore, Maryland.

Observing Stellar Motions in Dwarf Galaxy Companions to the Milky Way

The nearest galaxies to our own Milky Way are its companion dwarf galaxies, which are much smaller than the Milky Way. Van der Marel and his team plan to study the motions of stars in two of these dwarf galaxies, Draco and Sculptor. The orbits of the stars are governed by the gravity arising from the dark matter in each galaxy. By studying how the stars move, the researchers will be able to determine how the dark matter is distributed in these galaxies.

“How structures in the universe formed depends on the properties of the dark matter that comprises most of the mass in the universe,” explained van der Marel. “So we know there’s dark matter, but we don’t know what actually makes up this dark matter. We just know that there is something in the universe that has gravity and it pulls on things, but we don’t really know what it is.”

The team will study the distribution of dark matter in the centers of the dwarf galaxies to determine the temperature properties of this mysterious phenomenon. If dark matter is “cold,” its density will be very high near the centers of the galaxies. If dark matter is “warm,” it will be more homogenous throughout the area approaching the galactic centers.

At the same time Webb’s Near Infrared Camera (NIRCam) is studying the centers of Draco and Sculptor, another instrument, the Near Infrared Imager and Slitless Spectrograph (NIRISS), will be probing the outskirts of the dwarf galaxies. “These simultaneous observations will provide some insight into how stars move differently near the center and the outskirts of the dwarf galaxies,” said co-investigator Tony Sohn of STScI. “They will also allow two independent measures of the same galaxy, to check for any systematic or instrumental effects.”

Because Webb has approximately six times the light collection area of NASA’s Hubble Space Telescope, the team can measure the motions of stars much fainter than what Hubble can see. The more stars included in a study, the more accurately the team can model the dark matter that influences their motions.

Studying the Motion of Dwarf Galaxy Companions to Andromeda

The nearest large neighbor galaxy of our Milky Way, Andromeda has numerous dwarf galaxy companions, just as the Milky Way does. Van der Marel and his team plan to study how four of those dwarf galaxies are moving around Andromeda, to determine if they are grouped within a flat plane in space, or whether they are moving around Andromeda in all directions.

Unlike the first observation program, the team is not trying to measure how stars inside the dwarf galaxies move. In this study, they are trying to determine how the dwarf galaxies as a whole move around Andromeda. This will provide insights into the process whereby large galaxies form by accretion and accumulation of smaller galaxies, and how exactly that works.

In most models, dwarf galaxies that surround larger galaxies are not expected to lie in a plane. Typically, scientists would expect dwarf galaxies to fly around bigger galaxies in random ways. Slowly, these dwarf companions would lose energy and be accreted into the larger galaxy, which would grow larger still.

However, for both for the Milky Way and Andromeda, several studies have suggested that at least some fraction of the dwarf galaxies lie in a plane, and may even be rotating in that plane. One of the ways to determine if that’s true is to measure their three-dimensional motions. If the motions are actually in the plane, that would suggest that the dwarf galaxies will stay in a plane. But if the companion dwarfs appear to be in a plane but their motions are in all directions, that would indicate a chance alignment and not a long-lasting structure.

If the dwarf galaxies do line up in a plane, that can mean one of several things. It could be that a good fraction of the dwarf companions fell into orbit around Andromeda as a single group. If that were the case, the dwarfs would retain “memory” that they all fell in together, and they would exhibit similar dynamical properties right now.

Another possibility is that the dwarf galaxies of Andromeda formed as what are called “tidal dwarf galaxies.” These gravitationally bound collections of gas and stars form during mergers or interactions between large spiral galaxies. They are as massive as dwarf galaxies but are not dominated by dark matter, as scientists believe most of the dwarf galaxies around us are. It’s possible that a merger of two large galaxies with a lot of gas could form some dwarf galaxies that end up in a single planar structure, but that would be unusual, because scientists don’t think that tidal dwarf galaxies are the predominant type of dwarf galaxy in the universe. Dwarf galaxies are typically known to form inside of dark matter clouds called halos.

Either case could mean that galaxy formation may be more complicated than researchers sometimes think. Either would provide additional constraints on scientists who develop theoretical models of galaxy formation.

Webb’s Extreme Accuracy and Precision

In both programs, the team will push Webb to its limits in terms of accuracy and precision. “It’s a very tricky situation, because basically what we want to measure are very tiny motions,” explained co-investigator Andrea Bellini of STScI. “The accuracy we want to achieve is like measuring something that moves a few inches a year on the surface of the Moon, as seen from Earth.”

Both studies are Guaranteed Time Observations (GTO) programs allocated to the team of the Webb Telescope Scientist, Matt Mountain. He is also president of the Association of Universities for Research in Astronomy (AURA), headquartered in Washington, D.C.

The James Webb Space Telescope will be the world’s premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.


How is stellar mass of a galaxy obtained? - Astronomy

PSR J0348+0432 is a record-breaking binary system. Copyright: ESO/L. Calçada

With LISA we will survey compact stellar-mass binary systems in our own galaxy and better understand the structure of the Milky Way.

Very soon after activation, LISA will detect gravitational wave signals from known nearby binary compact stars. Because of their known positions and periods they serve as “verification binaries” ensuring in particular, predictable LISA signals. Signals are also certain to appear from populations of numerous and various remnants in our galaxy, including white dwarfs and neutron stars, which are known to exist from electromagnetic observations.

Extrapolation of known samples predicts that LISA will detect several thousand binaries. For hundreds of these, LISA will determine the orbital periods, mass parameters and distance, a rich trove of information for detailed mapping of our home galaxy.

These discoveries will also shed light on the outcome of the common envelope phase, on the progenitors of type Ia supernovae, and on tidal and non-gravitational influences on orbits associated with the internal physics of the compact remnants themselves.

LISA will detect only the brightest and nearest binaries as individual sources millions of others from across the Galaxy will blend together into a confusion foreground.


Fingerprint Dive into the research topics of 'Galaxy and Mass Assembly (GAMA): The stellar mass budget of galaxy spheroids and discs'. Together they form a unique fingerprint.

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1011 M· and group halo mass

1012.5 M·h-1. We further quantify the variation in spheroid-to-total mass ratio with group halo mass for central and satellite populations as well as the radial variation of this ratio within groups.",

Galaxy and Mass Assembly (GAMA) : The stellar mass budget of galaxy spheroids and discs. / Moffett, Amanda J. Lange, Rebecca Driver, Simon P. Robotham, Aaron S.G. Kelvin, Lee S. Alpaslan, Mehmet Andrews, Stephen K. Bland-Hawthorn, Joss Brough, Sarah Cluver, Michelle E. Colless, Matthew Davies, Luke J.M. Holwerda, Benne W. Hopkins, Andrew M. Kafle, Prajwal R. Liske, Jochen Meyer, Martin.

Research output : Contribution to journal › Article › peer-review

T1 - Galaxy and Mass Assembly (GAMA)

T2 - The stellar mass budget of galaxy spheroids and discs

N2 - We build on a recent photometric decomposition analysis of 7506 Galaxy and Mass Assembly (GAMA) survey galaxies to derive stellar mass function fits to individual spheroid and disc component populations down to a lower mass limit of log(M*/M·) = 8. We find that the spheroid/disc mass distributions for individual galaxy morphological types are well described by single Schechter function forms. We derive estimates of the total stellar mass densities in spheroids (ρspheroid = 1.24 ± 0.49 × 108 M· Mpc -3h0.7) and discs (ρdisc = 1.20 ± 0.45 × 108 M· Mpc -3h0.7), which translates to approximately 50 per cent of the local stellar mass density in spheroids and 48 per cent in discs. The remaining stellar mass is found in the dwarf 'little blue spheroid' class, which is not obviously similar in structure to either classical spheroid or disc populations. We also examine the variation of component mass ratios across galaxy mass and group halo mass regimes, finding the transition from spheroid to disc mass dominance occurs near galaxy stellar mass

1011 M· and group halo mass

1012.5 M·h-1. We further quantify the variation in spheroid-to-total mass ratio with group halo mass for central and satellite populations as well as the radial variation of this ratio within groups.

AB - We build on a recent photometric decomposition analysis of 7506 Galaxy and Mass Assembly (GAMA) survey galaxies to derive stellar mass function fits to individual spheroid and disc component populations down to a lower mass limit of log(M*/M·) = 8. We find that the spheroid/disc mass distributions for individual galaxy morphological types are well described by single Schechter function forms. We derive estimates of the total stellar mass densities in spheroids (ρspheroid = 1.24 ± 0.49 × 108 M· Mpc -3h0.7) and discs (ρdisc = 1.20 ± 0.45 × 108 M· Mpc -3h0.7), which translates to approximately 50 per cent of the local stellar mass density in spheroids and 48 per cent in discs. The remaining stellar mass is found in the dwarf 'little blue spheroid' class, which is not obviously similar in structure to either classical spheroid or disc populations. We also examine the variation of component mass ratios across galaxy mass and group halo mass regimes, finding the transition from spheroid to disc mass dominance occurs near galaxy stellar mass

1011 M· and group halo mass

1012.5 M·h-1. We further quantify the variation in spheroid-to-total mass ratio with group halo mass for central and satellite populations as well as the radial variation of this ratio within groups.


Watch the video: Η σύγκρουση με τον γαλαξία της Ανδρομέδας. Astronio X #2 (May 2022).