astronomy

PKS 2004−447

PKS 2004−447 is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand PKS 2004−447 rather than just read about it. In short: PKS 2004−447 is a narrow-line Seyfert 1 galaxy located in the constellation of Sagittarius. It has a redshift of (z) 0.24 and is the radio-loudest gamma ray emitting AGN known in the southern hemisphere.

Key takeaways

PKS 2004−447 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect PKS 2004−447 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of PKS 2004−447 from memory before moving on to harder problems.

Reference excerpt

PKS 2004−447 is a narrow-line Seyfert 1 galaxy located in the constellation of Sagittarius. It has a redshift of (z) 0.24 and is the radio-loudest gamma ray emitting AGN known in the southern hemisphere. It was first identified as an astronomical radio source during a very-long-baseline interferometry survey in 1989. The radio spectrum appears to be powerful and compact, making it a compact steep spectrum source. The X-ray emission for this source is described by a simple power-law in the (0.5-10 KeV) energy range. PKS 2004−447 is classified as a blazar. It is found variable on the electromagnetic spectrum and is a source of gamma ray activity. In October 2019, it was found to exhibit a gamma ray flare, reaching a highest flux of (1.3 ± 0.2) × 10−6 photon cm−2 s−1 at gamma-ray energies (0.1-300 GeV). A further study also showed during the post-flare in PKS 2004−447, there was the presence of Balmer, Paschen and Helium emission lines, with these lines vanishing within a period of 1.5 years. PKS 2004−447 has a core-jet structure with angular size measuring 40 mas. Its radio emission is found mainly dominated by the radio core, accounting for 42 percent of its total flux density at 1.4 GHz. There is a jet structure emerging from the core with a projected position angle measurement of -90°, which bends to -60° at 20 mas. This jet structure is further divided into two subcomponents enveloped completely from sight by the diffused emission. The host galaxy of PKS 2004−447 is a late-type barred disk galaxy with a stellar mass of ~ 7 × 1011 M☉, estimated from its K-band luminosity. It has a bulge showing a relatively low Sersic index of n ~ 1.2 with a bulge-to-total ratio of (B/T = 0.39 ± 0.02) for its J-band and (B/T = 0.44 ± 0.03) for its Ks-band. These values showed the bulge PKS 2004−447 is of pseudobulge morphology. The host galaxy shows two faint spiral arms and has an estimated black hole mass of 9 × 107 M☉.

References

External links PKS 2004−447 on SIMBAD PKS 2004−447 on NASA/IPAC Database

Illustrations

Worked examples

Example 1 — a first encounter with PKS 2004−447

Start with the simplest possible case. Write down what PKS 2004−447 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to PKS 2004−447 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about PKS 2004−447 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of PKS 2004−447

In research: PKS 2004−447 appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses PKS 2004−447 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: PKS 2004−447 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Active galaxies, Astronomical objects discovered in 1989, Blazars, so understanding it makes those chapters shorter.
In everyday life: Look for PKS 2004−447 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study PKS 2004−447 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what PKS 2004−447 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain PKS 2004−447 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is PKS 2004−447 in simple terms?

Why does PKS 2004−447 matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study PKS 2004−447?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on PKS 2004−447.