View source for NGC 404

{{Short description|Galaxy in the constellation Andromeda}}
{{Infobox galaxy
| name = [[New General Catalogue|NGC]] 404
| image = NGC 404 Hubble.jpg
| image_size = 280px
| caption = NGC 404 by [[Hubble Space Telescope]]; 1.68′ view
| credit = 
| epoch = [[J2000]]
| type = SA(s)0<sup>−</sup><ref name="ned">{{cite web
  | title=NASA/IPAC Extragalactic Database
  | work=Results for NGC 404
  | url=http://nedwww.ipac.caltech.edu/
  | access-date=2006-11-18 }}</ref>
| ra = {{RA|01|09|27.0}}<ref name="ned" />
| dec = {{DEC|+35|43|04}}<ref name="ned" />
| dist_ly = [[1 E22 m|10.0 ± 0.7]] [[light-year|Mly]] (3.07 ± 0.21 [[parsec|Mpc]])<ref name="jensenetal2003" /><ref name="karachentsevetal2004" /><ref name="Karachentsevetal2006">{{cite journal
  | author=Karachentsev, I. D. | author2=Kashibadze, O. G.
  | title=Masses of the local group and of the M81 group estimated from distortions in the local velocity field
  | journal=Astrophysics
  | date=2006
  | volume=49
  | issue=1
  | pages=3–18
  | bibcode=2006Ap.....49....3K   | doi=10.1007/s10511-006-0002-6
| s2cid=120973010
 }}</ref>{{Ref_label|A|a|none}}
| z = −48 ± 9 [[kilometer|km]]/[[second|s]]<ref name="ned" />
| appmag_v = 11.2<ref name="ned" />
| size_v = 3′.5 × 3′.5<ref name="ned" />
| constellation name = [[Andromeda (constellation)|Andromeda]]
| notes =
| names = [[Uppsala General Catalogue|UGC]] 718, [[Principal Galaxies Catalogue|PGC]] 4126<ref name="ned" />
}}

'''NGC 404''' is a [[field galaxy]]<ref name=1979A&A....74..235M>{{Cite journal |title= The structure of nearby groups of galaxies – Quantitative membership probabilities |author= Materne, J. |date= April 1979 |journal= Astronomy and Astrophysics |volume= 74 |number= 2 |pages= 235–243 |bibcode= 1979A&A....74..235M }}</ref> located about 10 million [[light year]]s away in the [[constellation]] [[Andromeda (constellation)|Andromeda]]. It was discovered by [[William Herschel]] in 1784, and is visible through small telescopes.<ref name="EncSci">[http://www.daviddarling.info/encyclopedia/M/Mirachs_Ghost.html Mirach's Ghost (NGC 404)], ''The Internet Encyclopedia of Science'', David Darling.  Accessed on line August 15, 2008.</ref> NGC 404 lies just beyond the [[Local Group]] and does not appear gravitationally bound to it. It is located  within 7 [[arc-minute]]s of second magnitude star [[Mirach]], making it a difficult target to observe or photograph and granting it the nickname "Mirach's Ghost".<ref name="EncSci" /><ref name="jpl">{{cite web
 | url = http://www.jpl.nasa.gov/news/news.php?feature=1926
 | title = 'Ghost of Mirach' Materializes in Space Telescope Image
 | author = <!--Staff writer(s); no by-line.-->
 | date = 31 October 2008
 | publisher = Jet Propulsion Laboratory
 | access-date = 26 September 2013
 | archive-date = 16 June 2017
 | archive-url = https://web.archive.org/web/20170616114412/https://www.jpl.nasa.gov/news/news.php?feature=1926
 | url-status = dead
 }}</ref>

== Physical characteristics ==

[[New General Catalogue|NGC]] 404 is a very isolated dwarf [[lenticular galaxy]], a bit more luminous and smaller than the [[Small Magellanic Cloud]].<ref name="Karachentsev2004">{{cite journal
    | author=Karachentsev, Igor D. | author2=Karachentseva, Valentina E. | author3=Huchtmeier, Walter K. | author4=Makarov, Dmitry I.
    | title=A Catalog of Neighboring Galaxies
    | journal=The Astronomical Journal
    | date=2003
    | volume=127
    | issue=4
    | pages=2031–2068
    | bibcode=2004AJ....127.2031K
    | doi=10.1086/382905| doi-access=free
    }}</ref> Unlike many other early-type galaxies, it is very rich in [[neutral hydrogen]], most of it concentrated in a pair of large rings around it.<ref name="Rio2004">{{cite journal
    | author=del Río, M. S. | author2=Brinks, E. | author3=Cepa, J.
    | title=High-Resolution H I Observations of the Galaxy NGC 404: A Dwarf S0 with Abundant Interstellar Gas
    | journal=The Astronomical Journal
    | date=2004
    | volume=128
    | issue=1
    | pages=89–102
    | bibcode=2004AJ....128...89D
    | doi=10.1086/421358|arxiv = astro-ph/0403467 | s2cid=118900337 }}</ref> It also has [[star formation]] both in its center<ref name="Bouchard2010">{{cite journal
    | author=Bouchard, A. | author2=Prugniel, P. | author3=Koleva, M. | author4=Sharina, M.
    | title=Stellar population and kinematics of NGC 404
    | journal=Astronomy & Astrophysics
    | date=2010
    | volume=513
    | pages=A54 | id=A54
    | bibcode=2010A&A...513A..54B
    | doi=10.1051/0004-6361/200913137|arxiv = 1001.4087 | s2cid=54924295 }}</ref> and in its outermost regions, albeit at a low level.<ref name="Thilker2010">{{cite journal
    | author=Thilker, David A. | display-authors=4 | author2=Bianchi, Luciana | author3=Schiminovich, David | author4=Gil de Paz, Armando | author5=Seibert, Mark | author6=Madore, Barry F. | author7=Wyder, Ted | author8=Rich, R. Michael | author9=Yi, Sukyoung | author10=Barlow, Tom | author11=Conrow, Tim | author12=Forster, Karl | author13=Friedman, Peter | author14=Martin, Chris | author15=Morrissey, Patrick | author16=Neff, Susan | author17=Small, Todd
    | title=NGC 404: A Rejuvenated Lenticular Galaxy on a Merger-induced, Blueward Excursion Into the Green Valley
    | journal=The Astrophysical Journal Letters
    | date=2010
    | volume=714
    | issue=1
    | pages=L171–L175
    | bibcode=2010ApJ...714L.171T
    | doi=10.1088/2041-8205/714/1/L171|arxiv = 1003.4985 | s2cid=51511487 }}</ref>

Both the outer gas disk and its star formation are assumed to have been triggered by one or several [[galaxy merger|mergers]] with smaller galaxies roughly 1 billion years ago<ref name="Thilker2010" /> and it has been proposed [[New General Catalogue|NGC]] 404 is a former [[spiral galaxy]] that was transformed into a lenticular one by that event.<ref name="Bouchard2010" />

==LINER emission==

NGC 404 contains a [[low-ionization nuclear emission-line region]] (LINER), a type of region that is characterized by [[spectral line]] emission from weakly [[ion]]ized atoms.<ref name="hoetal1997">{{Cite journal
 | last1 = Ho
 | first1 = Luis C.
 | last2 = Filippenko
 | first2 = Alexei V.
 | last3 = Sargent
 | first3 = Wallace L. W.
 | title = A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies
 | date = October 1997
 | volume = 112
 | pages = 315–390
 | url = http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997ApJS..112..315H
 | doi = 10.1086/313041
 | journal = The Astrophysical Journal Supplement
 | issue = 2
 |arxiv = astro-ph/9704107 |bibcode = 1997ApJS..112..315H | s2cid = 17086638
 }}</ref>
A [[nuclear star cluster]] is also present as well as (likely) a [[supermassive black hole]], with a mass of several tens of thousands [[solar mass]]es.<ref name="Seth2010">{{cite journal
    | author=Seth, Anil C. | display-authors=4 | author2=Cappellari, Michele | author3=Neumayer, Nadine | author4=Caldwell, Nelson | author5=Bastian, Nate | author6=Olsen, Knut | author7=Blum, Robert D. | author8=Debattista, Victor P. | author9=McDermid, Richard | author10=Puzia, Thomas | author11=Stephens, Andrew
    | title=The NGC 404 Nucleus: Star Cluster and Possible Intermediate-mass Black Hole
    | journal=The Astrophysical Journal
    | date=2010
    | volume=714
    | issue=1
    | pages=713–731
    | bibcode=2010ApJ...714..713S
    | doi=10.1088/0004-637X/714/1/713|arxiv = 1003.0680 | s2cid=118544269 }}</ref>

==Distance measurements==

At least two techniques have been used to measure distances to NGC 404.  The infrared [[surface brightness fluctuation]]s distance measurement technique estimates distances to spiral galaxies based on the graininess of the appearance of their bulges.  The distance measured to NGC 404 using this technique in 2003 is 9.9 ± 0.5 [[light-year|Mly]] (3.03 ± 0.15 [[parsec|Mpc]]).<ref name="jensenetal2003">{{cite journal
  | author=Jensen, Joseph B. | display-authors=4 | author2=Tonry, John L. | author3=Barris, Brian J. | author4=Thompson, Rodger I. | author5=Liu, Michael C. | author6=Rieke, Marcia J. | author7=Ajhar, Edward A. | author8=Blakeslee, John P.
  | title=Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations
  | journal=Astrophysical Journal
  |date=February 2003
  | volume=583
  | issue=2
  | pages=712–726
  | bibcode=2003ApJ...583..712J
   | doi=10.1086/345430
|arxiv = astro-ph/0210129 | s2cid=551714 }}</ref>

However, NGC 404 is close enough that [[red supergiants]] can be imaged as individual stars.  The light from these stars and knowledge of how they should compare to nearby stars within the [[Milky Way]] galaxy allows for direct measurement of the distance to the galaxy.  This method is referred to as the [[tip of the red giant branch]] (TRGB) method.  The estimated distance to NGC 404 using this technique is 10.0 ± 1.2 Mly (3.1 ± 0.4 Mpc).<ref name="karachentsevetal2004">{{cite journal
  | author=I. D. Karachentsev | author2=V. E. Karachentseva | author3=W. K. Hutchmeier | author4=D. I. Makarov
  | title=A Catalog of Neighboring Galaxies
  | journal=Astronomical Journal
  | date=2004
  | volume=127
  | issue=4
  | pages=2031–2068
  | bibcode=2004AJ....127.2031K  | doi=10.1086/382905
| doi-access=free
  }}</ref>  Averaged together, these distance measurements give a distance estimate of 10.0 ± 0.7 Mly (3.07 ± 0.21 Mpc).{{Ref_label|A|a|none}}

==Possible satellite==

In 2018 a possible satellite designated [[Donatiello I]] was identified.<ref name=ForbesDonatiello /> Donatiello I is a [[dwarf spheroidal galaxy]] with little recent star formation.<ref name=ForbesDonatiello /> Difficulty in establishing the exact distance to the galaxy leaves its status as a satellite unconfirmed.<ref name=ForbesDonatiello>{{Cite journal|last1=Romanowsky|first1=Aaron J.|last2=Forbes|first2=Duncan A.|last3=Haynes|first3=Martha P.|last4=Donatiello|first4=Giuseppe|last5=Beasley|first5=Michael A.|last6=Makarov|first6=Dmitry|last7=Carballo-Bello|first7=Julio A.|last8=Longeard|first8=Nicolas|last9=Boschin|first9=Walter|date=2018-12-01|title=Mirach's Goblin: Discovery of a dwarf spheroidal galaxy behind the Andromeda galaxy|journal=Astronomy & Astrophysics|language=en|volume=620|pages=A126|doi=10.1051/0004-6361/201833302|issn=1432-0746|bibcode=2018A&A...620A.126M|arxiv=1810.04741|s2cid=55255865}}</ref>

==Gallery==
<gallery>
File:NGC 404 PanS.jpg|[[Pan-STARRS]] image of NGC 404
</gallery> 

==Notes==
{{refbegin}}
<ol type="a">
<li>{{Note_label|A|a|none}}average(3.03 ± 0.15, 3.1 ± 0.4) = ((3.03 + 3.1) / 2) ± ((0.15<sup>2</sup> + 0.4<sup>2</sup>)<sup>0.5</sup> / 2) = 3.07 ± 0.21</li>
</ol>
{{refend}}

==References==
{{Reflist}}

==External links==
{{commonscat}}
* [http://www.daviddarling.info/encyclopedia/M/Mirachs_Ghost.html Encyclopedia of Astrobiology, Astronomy & Spaceflight Entry]
* [https://web.archive.org/web/20060206140956/http://astro.neutral.org/imagehtml/20041203_404.html Curdridge Observatory article]
* {{APOD |date=29 October 2008 |title=NGC 404: Mirach's Ghost}}
* {{WikiSky}}

{{Sky|01|09|27.0|+|35|43|04|10000000}}
{{Catalogs|NGC=404|UGC=718|PGC=4126}}
{{Ngc5}}
{{Andromeda (constellation)}}

{{DEFAULTSORT:NGC 0404}}
[[Category:Lenticular galaxies]]
[[Category:Field galaxies]]
[[Category:LINER galaxies]]
[[Category:Andromeda (constellation)]]
[[Category:NGC objects|0404]]
[[Category:UGC objects|00718]]
[[Category:Principal Galaxies Catalogue objects|04126]]
[[Category:Astronomical objects discovered in 1784|17840913]]
[[Category:Virgo Supercluster]]
[[Category:Discoveries by William Herschel]]