The Hubble Ultra-Deep Field (HUDF) is a deep-field image of a small region of space in the constellation Fornax, containing an estimated 10,000 galaxies. The original data for the image was collected by the Hubble Space Telescope from September 2003 to January 2004 and the first version of the image was released on March 9, 2004. [1] It includes light from galaxies that existed about 13 billion years ago, some 400 to 800 million years after the Big Bang.
The HUDF image was taken in a section of the sky with a low density of bright stars in the near-field, allowing much better viewing of dimmer, more distant objects. Located southwest of Orion in the southern-hemisphere constellation Fornax, the rectangular image is 2.4 arcminutes to an edge, [2] or 3.4 arcminutes diagonally. This is about one-tenth of the angular diameter of a full moon viewed from Earth (less than 34 arcminutes), [3] smaller than a 1 mm2 piece of paper held 1 m away, and equal to roughly one twenty-six-millionth of the total area of the sky. The image is oriented so that the upper left corner points toward north (−46.4°) on the celestial sphere.
In August and September 2009, the HUDF field was observed at longer wavelengths (1.0 to 1.6 μm) using the infrared channel of the recently fitted Wide Field Camera 3 (WFC3). This additional data enabled astronomers to identify a new list of potentially very distant galaxies. [4] [5]
On September 25, 2012, NASA released a new version of the Ultra-Deep Field dubbed the eXtreme Deep Field (XDF). The XDF reveals galaxies from 13.2 billion years ago, including one thought to have formed only 450 million years after the Big Bang. [6]
On June 3, 2014, NASA released the Hubble Ultra Deep Field 2014 image, the first HUDF image to use the full range of ultraviolet to near-infrared light. [7] A composite of separate exposures taken in 2002 to 2012 with Hubble's Advanced Camera for Surveys and Wide Field Camera 3, it shows some 10,000 galaxies. [8]
On January 23, 2019, the Instituto de Astrofísica de Canarias released an even deeper version [9] of the infrared images of the Hubble Ultra Deep Field obtained with the WFC3 instrument, named the ABYSS Hubble Ultra Deep Field. The new images improve the previous reduction of the WFC3/IR images, including careful sky background subtraction around the largest galaxies on the field of view. After this update, some galaxies were found to be almost twice as big as previously measured. [10] [11]
In the years since the original Hubble Deep Field, the Hubble Deep Field South and the GOODS sample were analyzed, providing increased statistics at the high redshifts probed by the HDF. When the Advanced Camera for Surveys (ACS) detector was installed on the HST, it was realized that an ultra-deep field could observe galaxy formation out to even higher redshifts than had currently been observed, as well as providing more information about galaxy formation at intermediate redshifts (z~2). [12] A workshop on how to best carry out surveys with the ACS was held at STScI in late 2002. At the workshop Massimo Stiavelli advocated an Ultra Deep Field as a way to study the objects responsible for the reionization of the Universe. [13] Following the workshop, the STScI Director Steven Beckwith decided to devote 400 orbits of Director's Discretionary time to the UDF and appointed Stiavelli as the lead of the Home Team implementing the observations.
Unlike the Deep Fields, the HUDF does not lie in Hubble's Continuous Viewing Zone (CVZ). The earlier observations, using the Wide Field and Planetary Camera 2 (WFPC2) camera, were able to take advantage of the increased observing time on these zones by using wavelengths with higher noise to observe at times when earthshine contaminated the observations; however, ACS does not observe at these wavelengths, so the advantage was reduced. [12]
As with the earlier fields, this one was required to contain very little emission from our galaxy, with little Zodiacal dust. The field was also required to be in a range of declinations such that it could be observed both by southern hemisphere instruments, such as the Atacama Large Millimeter Array, and northern hemisphere ones, such as those located on Hawaii. It was ultimately decided to observe a section of the Chandra Deep Field South, due to existing deep X-ray observations from Chandra X-ray Observatory and two interesting objects already observed in the GOODS sample at the same location: a redshift 5.8 galaxy and a supernova. The coordinates of the field are right ascension 3h 32m 39.0s, declination −27° 47′ 29.1″ (J2000). The field is 200 arcseconds to a side, with a total area of 11 square arcminutes, [12] and lies in the constellation of Fornax. [1]
Four filters were used on the ACS, centered on 435, 606, 775 and 850 nm, with exposure times set to give equal sensitivity in all filters. These wavelength ranges match those used by the GOODS sample, allowing direct comparison between the two. As with the Deep Fields, the HUDF used Directors Discretionary Time. In order to get the best resolution possible, the observations were dithered by pointing the telescope at slightly different positions for each exposure—a process trialled with the Hubble Deep Field—so that the final image has a higher resolution than the pixels on their own would normally allow. [12]
The observations were done in two sessions, from September 23 to October 28, 2003, and December 4, 2003, to January 15, 2004. The total exposure time is just under 1 million seconds, from 400 orbits, with a typical exposure time of 1200 seconds. [12] In total, 800 ACS exposures were taken over the course of 11.3 days, two per orbit; NICMOS observed for 4.5 days. All the individual ACS exposures were processed and combined by Anton Koekemoer into a set of scientifically useful images, each with a total exposure time ranging from 134,900 seconds to 347,100 seconds. To observe the whole sky to the same sensitivity, the HST would need to observe continuously for a million years. [1]
Camera | Filter | Wavelength | Total exposure time | Exposures |
---|---|---|---|---|
ACS | F435W | 435 nm | 134,880 s (56 orbits) | 112 |
ACS | F606W | 606 nm | 135,320 s (56 orbits) | 112 |
ACS | F775W | 775 nm | 347,110 s (144 orbits) | 288 |
ACS | F850LP | 850 nm | 346,620 s (144 orbits) | 288 |
The sensitivity of the ACS limits its capability of detecting galaxies at high redshift to about 6. The deep NICMOS fields obtained in parallel to the ACS images could in principle be used to detect galaxies at redshift 7 or higher but they were lacking visible band images of similar depth. These are necessary to identify high redshift objects as they should not be seen in the visible bands. In order to obtain deep visible exposures on top of the NICMOS parallel fields a follow-up program, HUDF05, was approved and granted 204 orbits to observe the two parallel fields (GO-10632). [14] The orientation of the HST was chosen so that further NICMOS parallel images would fall on top of the main UDF field.
After the installation of WFC3 on Hubble in 2009, the HUDF09 programme (GO-11563) devoted 192 orbits to observations of three fields, including HUDF, using the newly available F105W, F125W and F160W infra-red filters (which correspond to the Y, J and H bands): [5] [15]
Camera | Filter | Wavelength | Exposure time |
---|---|---|---|
WFC3 | F105W | 1050 nm ± 150 | 16 orbits, 14 usable |
WFC3 | F125W | 1250 nm ± 150 | 16 orbits |
WFC3 | F160W | 1600 nm ± 150 | 28 orbits |
The HUDF is the deepest image of the universe ever taken and has been used to search for galaxies that existed between 400 and 800 million years after the Big Bang (redshifts between 7 and 12). [1] [ obsolete source ] Several galaxies in the HUDF are candidates, based on photometric redshifts, to be amongst the most distant astronomical objects. The red dwarf UDF 2457 at distance of 59,000 light-years is the furthest star resolved by the HUDF. [16] The star near the center of the field is USNO-A2.0 0600–01400432 with apparent magnitude of 18.95. [17] [ better source needed ]
The field imaged by the ACS contains over 10,000 objects, the majority of which are galaxies, many at redshifts greater than 3, and some that probably have redshifts between 6 and 7. [12] The NICMOS measurements may have discovered galaxies at redshifts up to 12. [1]
The HUDF has revealed high rates of star formation during the very early stages of galaxy formation, within a billion years after the Big Bang. [12] It has also enabled improved characterization of the distribution of galaxies, their numbers, sizes and luminosities at different epochs, aiding investigation into the evolution of galaxies. [12] Galaxies at high redshifts have been confirmed to be smaller and less symmetrical than ones at lower redshifts, illuminating the rapid evolution of galaxies in the first couple of billion years after the Big Bang. [12]
The Hubble eXtreme Deep Field (HXDF), released on September 25, 2012, is an image of a portion of space in the center of the Hubble Ultra Deep Field image. Representing a total of two million seconds (about 23 days) of exposure time collected over 10 years, the image covers an area of 2.3 arcminutes by 2 arcminutes, [18] or about 80% of the area of the HUDF. This represents about one thirty-two millionth of the sky.
The HXDF contains about 5,500 galaxies, the oldest of which are seen as they were 13.2 billion years ago. The faintest galaxies are one ten-billionth the brightness of what the human eye can see. The red galaxies in the image are the remnants of galaxies after major collisions during their elderly years. Many of the smaller galaxies in the image are very young galaxies that eventually developed into major galaxies, similar to the Milky Way and other galaxies in our galactic neighborhood. [6]
Fornax is a constellation in the southern celestial hemisphere, partly ringed by the celestial river Eridanus. Its name is Latin for furnace. It was named by French astronomer Nicolas Louis de Lacaille in 1756. Fornax is one of the 88 modern constellations.
The Hubble Deep Field (HDF) is an image of a small region in the constellation Ursa Major, constructed from a series of observations by the Hubble Space Telescope. It covers an area about 2.6 arcminutes on a side, about one 24-millionth of the whole sky, which is equivalent in angular size to a tennis ball at a distance of 100 metres. The image was assembled from 342 separate exposures taken with the Space Telescope's Wide Field and Planetary Camera 2 over ten consecutive days between December 18 and 28, 1995.
The Near Infrared Camera and Multi-Object Spectrometer (NICMOS) is a scientific instrument for infrared astronomy, installed on the Hubble Space Telescope (HST), operating from 1997 to 1999, and from 2002 to 2008. Images produced by NICMOS contain data from the near-infrared part of the light spectrum.
The Hubble Deep Field South is a composite of several hundred individual images taken using the Hubble Space Telescope's Wide Field and Planetary Camera 2 over 10 days in September and October 1998. It followed the great success of the original Hubble Deep Field in facilitating the study of extremely distant galaxies in early stages of their evolution. While the WFPC2 took very deep optical images, nearby fields were simultaneously imaged by the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS).
APM 08279+5255 is a very distant, broad absorption line quasar located in the constellation Lynx. It is magnified and split into multiple images by the gravitational lensing effect of a foreground galaxy through which its light passes. It appears to be a giant elliptical galaxy with a supermassive black hole and associated accretion disk. It possesses large regions of hot dust and molecular gas, as well as regions with starburst activity.
The Extended Groth Strip is an image of a small region between the constellations of Ursa Major and Boötes, based on the results of a series of observations by the Hubble Space Telescope. It covers an area 70 arcminutes across and 10 arcminutes wide, which correlates to a patch of sky roughly the width of a finger stretched at arm's length. The image was assembled from over 500 separate exposures taken with the Space Telescope's Advanced Camera for Surveys at 63 different pointings, spread out over the course of one year from June 2004 to March 2005. The complete image at the highest resolution in JPEG format is nearly 250 megabytes.
A1689-zD1 is a galaxy in the Virgo constellation. It was a candidate for the most distant and therefore earliest-observed galaxy discovered as of February 2008, based on a photometric redshift.
The Great Observatories Origins Deep Survey, or GOODS, is an astronomical survey combining deep observations from three of NASA's Great Observatories: the Hubble Space Telescope, the Spitzer Space Telescope, and the Chandra X-ray Observatory, along with data from other space-based telescopes, such as XMM Newton, and some of the world's most powerful ground-based telescopes.
The Chandra Deep Field South (CDF-S) is an image taken by the Chandra X-ray Observatory satellite. The location was chosen because, like the Lockman Hole, it is a relatively clear "window" through the ubiquitous clouds of neutral hydrogen gas in the Milky Way galaxy, which allows observers to clearly see the rest of the universe in X-rays. The image is centered on RA 3h 32m 28.0s DEC −27° 48′ 30″ (J2000.0), covering 0.11 square degrees, measuring 16 arcminutes across. This patch of sky lies in the Fornax constellation.
UDFy-38135539 is the Hubble Ultra Deep Field (UDF) identifier for a galaxy which was calculated as of October 2010 to have a light travel time of 13.1 billion years with a present proper distance of around 30 billion light-years.
UDF 423 is the Hubble Ultra Deep Field (UDF) identifier for a distant spiral galaxy. With an apparent magnitude of 20, UDF 423 is one of the brightest galaxies in the HUDF and also has one of the largest apparent sizes in the HUDF.
UDFj-39546284 is a high-redshift Lyman-break galaxy discovered by the Hubble Space Telescope in infrared Hubble Ultra-Deep Field (HUDF) observations in 2009. The object, located in the Fornax constellation, was identified by G. Illingworth, R. Bouwens and the HUDF09 Team during 2009 and 2010. It was reported with a redshift of z~10 using Hubble and Spitzer Space Telescope photometric data, with later reports in 2012 suggesting a possibly higher redshift of z = 11.9 Although doubts were raised that this galaxy could instead be a low-redshift interloper with extreme spectral emission lines producing the appearance of a very high redshift source, later spectroscopic observations by the James Webb Space Telescope's NIRSpec instrument in 2022 confirmed the galaxy's high redshift to a spectroscopically confirmed estimate of z = 11.58.
HUDF-JD2 is a distant, massive, post-starburst galaxy that was discovered with the Hubble Ultra Deep Field (HUDF) image. It was the most distant galaxy identified in the HUDF, in 2005. It is located at 03h 32m 38.7268s −27° 48′ 39.885″ in the constellation of Fornax.
MACS0647-JD is a galaxy with a redshift of about z = 10.7, equivalent to a light travel distance of 13.26 billion light-years. If the distance estimate is correct, it formed about 427 million years after the Big Bang.
The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) is the largest project in the history of the Hubble Space Telescope, with 902 assigned orbits of observing time. It was carried out between 2010 and 2013 with two cameras on board Hubble – WFC3 and ACS – and aims to explore galactic evolution in the early Universe, and the very first seeds of cosmic structure at less than one billion years after the Big Bang.
Bedin I is a dwarf spheroidal galaxy located in the constellation Pavo. It is situated around 28.38 million light-years from Earth, behind the globular cluster NGC 6752. Bedin I is possibly one of the oldest galaxies known, having formed around 10–13 billion years ago, and is one of the most isolated dwarf galaxies known, situated around 2.12 million light-years away from NGC 6744, its nearest neighbor with which it may be physically associated. As such, it has been deemed by astronomers as a "fossil" from the early universe. It was accidentally discovered by Italian astronomer Luigi Bedin, whose team was studying white dwarfs in NGC 6752 using the Hubble Space Telescope in September 2018; the discovery was announced in a paper published in January 2019.
The Hubble Legacy Field is an image of a small region of space in the constellation Fornax, containing an estimated 265,000 galaxies. The original release was composed of Hubble Space Telescope data accumulated over a 16-year period. Looking back approximately 13 billion years it has been used to search for galaxies that existed at that time. The image was taken in a section of the sky with a low density of bright stars in the near-field, allowing much better viewing of dimmer, more distant objects. It builds on the data collected for the Hubble Ultra-Deep Field, the Hubble eXtreme Deep Field and the Great Observatories Origins Deep Survey.
Webb's First Deep Field is the first operational image taken by the James Webb Space Telescope (JWST). The deep-field photograph, which covers a tiny area of sky visible from the Southern Hemisphere, is centered on SMACS 0723, a galaxy cluster in the constellation of Volans. Thousands of galaxies are visible in the image, some as old as 13 billion years. It is the highest-resolution image of the early universe ever taken. Captured by the telescope's Near-Infrared Camera (NIRCam), the image was revealed to the public by NASA on 11 July 2022.
JADES-GS-z13-0 is a high-redshift Lyman-break galaxy discovered by the James Webb Space Telescope (JWST) during NIRCam imaging for the JWST Advanced Deep Extragalactic Survey (JADES) on 29 September 2022. Spectroscopic observations by JWST's NIRSpec instrument in October 2022 confirmed the galaxy's redshift of z = 13.2 to a high accuracy, establishing it as the oldest and most distant spectroscopically-confirmed galaxy at the time, with a light-travel distance of 13.4 billion years. Due to the expansion of the universe, its present proper distance is approximately 33 billion light-years. In 2024, two older and more distant galaxies, JADES-GS-z14-0 and JADES-GS-z14-1, were found.