User talk:Hmedina19/sandbox

On your sandbox page there is only the reference to an alternative explanation of velocity dispersion. You should either include one in your initial discussion or remove the alternative bit. I would suggest few commas to smooth the reading as with the second paragraph in the evidence of dark matter section.

In the lead section, if objects such as these were observed in galaxies other than the Milky Way and M31, would they also be classified as dSph? Maybe look for or more general definition of dSph galaxies and include / cite it.

In the section of discovery, another trouble with discovering them is the distance and apparent magnitude of them. Even though globular clusters are similar in luminosity and surface brightness they are significantly closer and thus appear brighter. Drbingbing (talk) 06:53, 12 March 2017 (UTC)

Hi, overall it's a good article. Here are a few comments and suggestions of items that I think could be further improved to help the article to be even better:

I believe some of not all of these dwarf sheroidals have Wiki entries which you could link in your article.
 * Ursa Minor, Carina, Sculptor, Fornax, etc.:

add an "a" before mass to light ratio
 * In this sentence: "Their luminosities are so low that Ursa Minor, Carina, and Draco, the known dwarf spheroidal galaxies with the lowest luminosities, have mass-to-light ratios (M/L) greater than that of the Milky Way.[2]"

I would revise the last part of the sentence to make it flow better. I would recommend to end the sentence after "galaxy" and then start a new sentence. I.e. "All consist of stars generally much older than 1-2 Gyr which formed over the span of many gigayears.[2]" Or you could separate the sentence by a semicolon, but you'd have to delete the "and".
 * For this sentence: "Each dSph is named after constellations they are discovered in, such as the Sagittarius dwarf spheroidal galaxy, and all consist of stars generally much older than 1-2 Gyr that formed over the span of many gigayears.[2]"


 * This sentence is missing an "and" before "formed": "For example, 98% of the stars in the Carina dwarf spheroidal galaxy are older than 2 Gyr formed over the course of three bursts around 3, 7, and 15 Gyr ago.[2]"


 * You have boldened the 10^7 solar mass number in the first paragraph under dark matter evidence. I feel the boldening of this number is a bit much, as it sticks out and catches your attention right away. It just looks a little off. I would undo that.

Before "many astronomers" you either need to change the comma to a semicolon, and perhaps add the word "however". I.e. ....and a star cluster; however many astronomers decide this depending on the object's dynamics:....
 * In this sentence: "Although at fainter luminosities of dwarf spheroidal galaxies, it is not universally agreed upon how to differentiate between a dwarf spheroidal galaxy and a star cluster, many astronomers decide this depending on the object's dynamics:"

I would try to rephrase the last part where is says different class of object from glob cluster. Maybe something along the lines: "In the current predominantly accepted Lambda cold dark matter cosmological model, the presence of dark matter is often cited as a reason to classify dwarf spheroidal galaxies as a different class of object. In comparison, globular clusters show little to no signs of dark matter."
 * This sentence: "...the presence of dark matter is often cited as a reason to classify dwarf spheroidal galaxies as a different class of object from globular clusters, which show little to no signs of dark matter."

I would say "gravitational effects are small." Don't use the past tense, unless something has changed sine they were last measured.
 * In this sentence: "Further evidence of the prevalence of dark matter in dSphs includes how a study of the Fornax dwarf spheroidal galaxy revealed that the Fornax dSph can be assumed to be in dynamic equilibrium to estimate mass and amount of dark matter since the gravitational effects of the Milky Way were small.[9]"

sort of repeat what the immediately preceding sentence was already stating. I would cut it or try to consolidate both sentences.
 * This next sentence: "The tidal effects of the Milky Way on the Fornax galaxy's stellar structure are very small, especially with respect to how the Milky Way's galactic field affects the dark matter in the Fornax galaxy.[9]"

Does it really add to the article if Sextans dsph was the eighth to be discovered? I feel this would be too specific to be mentioned in a general article describing dwarf spheroidals. Little facts like that should be listed in the article on Sextans, but not here. It would also shorten your article a bit.
 * On this sentence: "For example, the Sextans dwarf spheroidal galaxy, discovered in 1990 as the eighth dSph to have been found, has a velocity dispersion of 7.9±1.3 km/s, ..."

Same thought as mentioned in my penultimate bullet point; I don't think mentioning when and how it was discovered adds to your general article on dwarf shperoidals.
 * "Similar to Sextans, previous studies of Hercules dwarf spheroidal galaxy, a dSph discovered in 2006 by the Sloan Digital Sky Survey, reveal that its orbital path does not correspond to the mass contained in Hercules.[10] "

And those are all the comments and suggestions I have. Hopefully it will help you in finalizing your Wiki entry. Let me know if you have any questions or need some suggestions.

Cheers, Thomas

ThomasUCI (talk)

Also, you should put all your references in a new section titled "References".

ThomasUCI (talk) —Preceding undated comment added 06:48, 17 March 2017 (UTC)