Supermassive Black Hole Control Star Formation in Large Galaxies Menzi Ngcamphalala NGCMEN001 September 15

Supermassive Black Hole Control Star Formation
in Large Galaxies
Menzi Ngcamphalala NGCMEN001 September 15, 2018
Source Article :
Title : Black-hole-regulated star formation in massive galaxies
Authors : Ignacio Martn-Navarro, Jean P. Brodie, Aaron J. Romanowsky,
Tomas Ruiz-Lara Glenn van de Ven
First Author’s Institution : University of California Observatories
Status : nature International journal of science
1 Introduction
When the galaxy evolves the formation of stars process get shutted down. A
new investigation disclosed that using a mass of a black hole that is from the
center of a galaxy, turn o of the star formation can be determined how shortly
can it take place, since it is known that there is a central supermassive black
hole in every massive galaxy. The shut down is thought to occur when the
energy from a compact region at the center of a galaxy that has much higher
luminosity of the electromagnetic spectrum (AGN)
ow into a galaxy, so this
occur by dissipating and heating the gas that would condense as it cool into a
star. Prof Jean Brodie said that this evidence is the rst direct observational,
where the eect of black hole on the process of star formation history of the
galaxy can be seen. The new results disclosed that every generation of a galaxy
is aected, this is because throughout the life of a galaxy there is a continuous
interaction between the star formation and black hole activity.
2 Method
Martin-Navarro determined the star formation histories of the galaxies by ana-
lyzing the detailed spectra of their light acquired by the Hobby-Eberly Telescope
massive galaxy survey. Astronomers use spectroscopy to measure and separate
dierent wavelengths of light from an ob ject. Martin-Navarro analyzed the
spectrum of each galaxy by using computational techniques, he then retrieved
its star formation history by tting the spectroscopic data in the best combina-
tion of stellar populations. He mentioned that this helps to show the amount
1

Figure 1: The intensity of a supermassive black hole is shown in this gure
of Centaurus A, one of the dynamic galactic nuclei nearest to Earth. The
picture consolidate information from a few telescopes at various wavelengths,
demonstrating jets and lobes controlled by the supermassive black hole at the
center of the galaxy.
of light that is from stellar population of dierent ages. The usual size of the
under-massive is RU M
e = 2
:49 0:37 kpc and over-massive black-hole galaxies
is ROM
e = 2
:69 0:34 kpc are consistent with average population of galaxies
with the known masses of ( RBH
e = 2
:71 0:22 kpc ). The mass of suppermas-
sive black hole scales is shown in gure 2 with the stellar speed dispersion of
their host galaxies. Figure 2 express how over-massive and under-massive are
lying below and above the line of best tting. Over-massive have more massive
central black holes, while under-massive have black-hole galaxies with light sup-
permassive black holes. The method where by observed spectrum of a galaxy
is decomposed as a temporal series of single population models is called Stellar
Content and Kinematics via Maximum A Posteriori likelihood (STECKMAP).
STECKMAP was used to measure star formation history. Wavelengths between
460 and 550 nmwas used for spectroscopic analysis. The Hobby{Eberly Tele-
scope Massive Galaxy Survey (HETMGS) was used with long-slit optical spectra
to conduct analysis of stellar population, depending on a slit-width but values
of data resolution varied between 4 :8 and 7 :5. Infared K-band photometry was
used to calculate the size of all galaxies (in a homogenous way).
The ma jority of ob jects (about 85%) classied as over-massive or under-
massive using our best-tting relation are also over-massive or under-massive
3 Results
After Martin determined the star formation histories of galaxies by analyzing
the spectrum of each galaxy, he then found the noticeable dierences when he
compared the histories of the star formation of galaxies with dierent masses
of black holes. The dierences only corresponded with the mass of a black
hole not the size, or shape of galaxy. The results also showed that for galaxies
2

Figure 2: The stellar speed scattering of galaxies rmly associates with the mass
of their supermassive black holes . Data points relates toward the 74 HETMGS
galaxies with estimated black hole masses and high-quality spectra.Galaxies
more than +0 :2 dex over this best-tting connection have black holes more
massive than anticipated for their speed scattering, and consequently are called
over-massive black holes galaxies (red). On the other hand, black hole facilitat-
ing less-massive black holes than the normal populace (by 0 :2 dex or past) are
called under-massive black holes (blue).
with similar mass of stars but unique mass of a black hole in the center, those
galaxies with greater black holes were extinguished before and speedier than
those with littler black holes. The star formation kept going longer in those
galaxies with little central black holes. The luminosity of a supermassive black
hole appear when it actively guzzling up the matter from its host inner regions
of the galaxy. AGN highly varies and are dependent on black hole size, accretion
rate of new material that falls into a black hole. Martin further explained that
they used the mass of a black hole as a proxy for the energy that AGN put
into the galaxy. More energetic feedback from AGN results from the accretion
unto more massive black hole. The stellar speed scattering of galaxies rmly
associates with the mass of their supermassive black holes . Data points relates
toward the 74 HETMGS galaxies with estimated black hole masses and high-
quality spectra. They have made utilization of the connection between black
holes mass and star formation histories to demonstrate that the evolution of
star formation in massive galaxies over inestimable time is driven by black hole
activities. Interestingly, black-hole masses and star formation seem to be related
as early as z 5.
Figure 3 show the evolution of star formation over cosmic time is strongly
coupled to the mass of the central black hole. Galaxies with over-massive black
holes experienced more intense star formation rates in the very early Universe
(look-back times of 10 Gyr or more) than did galaxies with less-massive black
holes. The measurements shown in Figure 3 probe the star formation processes
3

Figure 3: This gure show how star formation rates and cumulative stellar mass
have evolved in over-massive (red), in standard (orange) and in under-massive
(blue) black-hole galaxies. Figure a, show the evolution of the star formation
rate (SFR) as a function of look-back time; while b, the cumulative mass dis-
tribution for the three types of galaxy. The dierences in formation timescales
such as those shown in this gure do not depend on galaxy environment. This
gure represent the Evolution of star formation over cosmic time.
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within massive haloes since the early Universe. Interestingly, black-hole masses
and star formation seem to be related as early as z 5. Figure 3 shows that
the evolution of star formation over cosmic time is strongly coupled to a mass of
the central black hole. Masses of black holes was measured using many dierent
methods but without detailed information on the stellar population properties.
Their nal sample consisted of all HETMGS galaxies for which there are direct
measurements of black-hole masses, and for which they can also determine their
star formation histories. There are 74 in total, probing total stellar masses from
M 1x 10 10
M to M
2x 10 12
M:
4 Conclusion
Aaron Romanowsky said the exact nature of the feedback from black holes that
terminates formation of stars process is still unknown. Romanowsky further said
black hole can put energy out into the galaxy in the dierent ways, there are
many ideas from (theorists) that talk about how the quenching of star formation
happens, there still more work that need to be done in order to t the new
observations into models. Their outcomes show that there might be a causal
origin for the watched scaling relations between galaxy properties and black
hole mass, oering observational help for AGN-based extinguishing mechanism.
The quantity of over-massive, standard and under-massive black hole galaxies is
comparable, at 25, 24 and 25 ob jects, separately. Star formation in over-massive
black-hole galaxies was quenched earlier, with these galaxies reaching 95% of
their nal mass about 4 Gyr earlier, on average, than under-massive black-hole
galaxies, as shown by the cumulative mass distributions in gure 3.
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